Aquatic plants are divided into higher (Cormobionta) and lower (Thallobionta). The latter include all types of algae. They are one of the oldest representatives of the flora. Their main feature is spore reproduction, and the peculiarity lies in the ability to adapt to various conditions. There are types of algae that can live in any water: salty, fresh, dirty, clean. But for aquarists, they become a big problem, especially in the case of their violent growth.

There are types of algae that can live in any water: salty, fresh, dirty, clean.

Main characteristic

Depending on the species of algae, some are attached to underwater surfaces, while others live freely in the water. Cultures may contain only green pigment, but there are species with different pigments. They color algae pink, blue, purple, red and almost black.

The biological processes occurring in the aquarium are the basis for the independent appearance of algae. They are introduced when fish are fed live food or newly acquired aquatic plants.

Some algae look like a fluffy bunch, others resemble a spreading carpet, and others look like a mucous membrane. There are flat, thallus, branching, filamentous cultures. Unlike higher plants, they do not have roots, stems or leaves. Their shape, structure and size are varied. There are species that can only be seen under a microscope. In the natural environment, plants reach several meters in length.

Algae classification

Each species has its own requirements for the environment in which they grow - to the temperature of the liquid, to the intensity and duration of lighting. An important factor is the chemical composition of water.

The imbalance of algae in the aquarium indicates the occurrence of unfavorable conditions in it. Excessive increase in them in the tank worsens the quality of the water, which adversely affects the health of the inhabitants of the aquarium. An algal outbreak can be caused by:

1. Unregulated aquarium lighting. This is a lack of daylight hours or its excess.
2. Excess organics in the container. They may be in the form of leftover food, dead aquarium plants, fish sewage.
3. decomposition of organic matter. The appearance of nitrites and ammonia in the aquarium.

Having identified which factor is the cause of the appearance of crops, it is necessary to eliminate it or minimize it as much as possible.

The imbalance of algae in the aquarium indicates the occurrence of unfavorable conditions in it.

Algae are divided into 12 types. The aquarium is most often characterized by the presence of three main types of cultures.

Their presence is predictable where there is water, light and nutrients.

Green group

This is the most common and most diverse group of plants in structure and form, which has about 7 thousand species. They come in non-cellular, unicellular and multicellular forms. Algae form colonies on glass or soil.

Their peculiarity is that almost all cultures appear as a result of excessive lighting. They have a green color, despite the content in them, in addition to green chlorophyll, of a yellow pigment. Algae color the liquid green or brick green.

There are marine and freshwater species. Names of algae that are in the aquarium:

The main reason for the appearance of most species of green algae is excessive lighting, so when the biological balance is restored, this problem can quickly disappear.

Diatoms (brown) plants

If the liquid in the container has to be changed frequently, because it quickly becomes cloudy, - brown algae in it. It not only spoils the interior of the aquarium, but also causes inconvenience to its inhabitants. These are single-celled microscopic organisms that multiply rapidly and create a slimy coating on the leaves of aquarium plants and tank glasses. They live singly or in colonies in the form of a ribbon, thread, chain, film, bush.

On the initial stage the appearance of plaque in the container, it is easily removed, and in advanced cases it becomes multi-layered, and it can be difficult to get rid of it. Brown plants will not harm aquarium animals, but they are dangerous for aquarium plants. Plaque on cultures interferes with photosynthesis, which leads to their death.

Reproduction of diatoms is carried out using division. Plant cells have a hard shell with a silica composition. Their dimensions are at least 0.75 µm, maximum 1500 µm. This culture is easy to distinguish by the shell in the form of dots, chambers, strokes, edges arranged with geometric regularity.

Navicula live almost everywhere, start up in spring and autumn.

In nature, about 25 thousand varieties of brown crops. Most often found in containers:

1. Navicula. This genus has about 1 thousand species of algae. Planted in containers in spring and autumn. The method of reproduction is cell division. Cells are different in shape, shell structure and structure. They serve as food for the inhabitants of the aquarium, and they themselves eat phototrophically.
2. Pinnularia. Early autumn and summer are the time of appearance for this genus. As a result of cell division, each receives one leaflet from the mother cell. Single cells are rarely connected into ribbons. About 80 species of these algae are known.
3. Cymbella. The genus is a single free-living cell, which is sometimes attached to the substrate by a mucous stalk. In addition, they may be enclosed in gelatinous tubes.

Brown algae develop in those reservoirs where the water does not change in time or the lighting is poor. Their distribution is affected by the dense population of the aquarium, a large number of organics, clogged filter.

Red or "crimson"

Red algae, or purple algae, is a small species of crops, the vast majority are multicellular, numbering up to 200 varieties. All purples are divided into 2 classes, each of which contains 6 orders. They settle on the stems and ends of the leaves of aquarium plants, stones, grow quickly and multiply intensively.

The reason for the appearance of this type of plant is an excess of organic matter in the water, improperly installed lighting or overpopulation in the tank. These crops pose a danger to its inhabitants, so they must be destroyed in a timely manner.

Crimson, depending on the combination of pigments, change color from bright red to bluish-green and yellow, and freshwater ones are usually green, blue or brownish-black. A feature of plants is their complex development cycle. As a rule, these crops grow attached to other plants, stones, tanks. You can find colonies of cultures in the form of mucous deposits.

Red algae, or purple algae, is a small species of crops, the vast majority are multicellular, numbering up to 200 varieties.

For aquarists, there are two types of disaster:

1. Black beard. At the initial stage, it is a single black bushes that are concentrated in one place, or they can be scattered throughout the tank. If you do not start to fight it, then with the help of rhizoids, the culture clings to the substrate, as if growing into it. Very often, these algae appear after the purchase of new aquarium plants, or if the rules for caring for the tank are neglected.
2. Vietnamese. Such aquarium algae are filamentous species. Based on their appearance, aquarists call them bush, beard or brush. The plants come in a variety of colors and reproduce very quickly by spores. The culture prefers to sit on the tips of aquarium plants or tank decor.

The appearance of any kind of algae indicates microclimate problems in the tank. It takes months to fight some plants, while others can be quickly and easily disposed of.

3.2. Algae (Algae)

3.2.1. The main features and systematics of algae

Algae is a huge group of plants of great biological importance and very important for humanity (section 3.2.8). They are the most primitive of plants and do not have a body division into stem, root and leaves. Therefore, initially they were combined together with fungi in the department Thallophyta (see note on p. 43). However, after new scientific discoveries, it became clear that algae are no less diverse than all other groups of plants combined, and that they have very little common features. It is probably best to consider algae as all photosynthetic oxygen-producing organisms that have evolved in the aquatic environment and have fully mastered it. True, some algae also came to land, but on a global scale, the productivity of coastal and terrestrial forms is negligible in comparison with the productivity of oceanic and freshwater algae. If one adheres to this point of view, then blue-green algae (Cyanophyta) should also be included in the group of algae. However, since these algae are prokaryotes, it has been proposed to call them cyanobacteria (Cyanobacteria) in order to somehow distinguish them from eukaryotic algae. At the same time, one very important fact is overlooked, namely, that blue-green algae release oxygen during photosynthesis, while all other photosynthetic prokaryotes do not. In order for water to split into hydrogen and oxygen, the presence of chlorophyll and photosystem II (Sec. 9.4.2) is necessary, which is an important advantage over photosynthetic bacteria. Very little is known about how this advantage was achieved, although some forms have been found that are intermediate between blue-green algae and bacteria. This interpretation of the relationship between blue-green algae and other plants, including other algae, is supported by evidence supporting the symbiotic theory that plant chloroplasts originated from blue-green algae (Section 9.3.1).

Summing up, we can say that the term "algae" in itself is convenient, but its use in taxonomy introduces unnecessary complications. Blue-green algae should be classified as prokaryotes, and all other algae as eukaryotes.

Fortunately, eukaryotic algae fall quite naturally into well-distinguished groups, the main distinguishing feature being a set of photosynthetic pigments. In modern systematics, such groups have received the status of departments. Relationships between departments have not yet been elucidated, and this issue is very important in order to understand the origin of higher plants and the relationship between prokaryotes and eukaryotes.

All departments are listed in Fig. 3.11, and in fig. 3.12 gives modern ideas about what connections exist between these departments. The main features of algae and some of the main departments are given in table. 3.4.

3.2.2. asexual reproduction of algae

Algae have both asexual and sexual reproduction. The main types of asexual reproduction are briefly listed below, from the simplest to the most complex.

Vegetative reproduction. In some colonial forms, colonies can break up into separate fragments, which give rise to new smaller colonies. In larger algae, such as Fucus, additional thalli can form on the main thallus, which break off and form new organisms.

Fragmentation. This phenomenon is observed in filamentous algae such as blue-green algae and Spirogyra. The thread splits in a strictly defined way along, and two new threads are formed. This phenomenon can be considered as one of the forms of vegetative reproduction.

Binary division. In this case, a unicellular organism divides into two identical halves, while the nucleus divides mitotically. A longitudinal division of this type is observed in Euglena.

zoospores. These are motile spores with flagella. They form in many algae, such as Chlamydomonas, and in some fungi (see Oomycota, Table 3.2).

aplanospores. These immobile spores are formed, for example, in some brown algae.

3.2.3. Sexual reproduction in algae

Sexual reproduction combines the genetic material of two separate individuals of the same species. The easiest way of such reproduction is in algae; it consists in the fusion of two morphologically (ie, structurally) identical gametes. Such a process is called isogamy, and the gametes isogametes. Spirogyra isogamous and some species of Chlamydomonas.

If one of the gametes is less mobile or larger than the other, then this process is called anisogamy. In Spirogyra, the gametes do not differ in structure, but one of them moves, while the other is immobile. This can be seen as physiological anisogamy. There is another option, when one gamete is large and immobile, and the second is small and mobile. Such gametes are called female and male, and the process itself is called oogamy. Fucus oogamnas and some species of Chlamydomonas. Female gametes are large because they contain a supply of nutrients necessary for the development of the zygote after fertilization.

All three types of sexual reproduction correspond to an increase in the complexity of body structure, and therefore oogamy, although found in some simple algae, such as Chlamydomonas, is generally more common in more complex algae, such as Phaeophyta. Oogamy is the only mode of sexual reproduction in plants that are more highly organized than algae.

Unfortunately, the terminology used to describe gametes and reproductive organs in plants is very confusing, especially in algae. Below we will explain only the main terms.

In fungi and lower plants (algae, bryophytes and ferns), gametes are formed in special structures called gametangia. The male gametangia is called the antheridium, and the female gametanium is called the oogonium or archegonium.

Oogony* is a simple female gametangium that occurs in many algae and fungi, and the female gametes or gametes that are in it are called oospheres. The fertilized oosphere is called oospore; it turns into a thick-walled resting spore, capable of surviving adverse conditions. Common name for the female gamete - egg or egg, although sometimes the term "oosphere" is used to refer to the egg; however, this is not entirely accurate.

* (Oogonia are also called ovarian cells, from which oocytes are formed in animals (see Chapter 20).)

Archegonium- this is a more complex female gametangy, which is characteristic of bryophytes, ferns and many gymnosperms; archegonium will be described later in this chapter.

AT antheridia male gametes are produced which are called antherozoids or spermatozoa. They are mobile because they are equipped with one or more flagella. Such gametes are characteristic of fungi, algae, bryophytes, ferns, and some gymnosperms. In animals, the male gametes are called spermatozoa or sperm. The listed names are shown in fig. 3.13.

For the purposes of this chapter, it is not so important how to name different gametes of the same sex, so it is quite enough to distinguish between spermatozoa, i.e. all male gametes, and eggs, i.e. all female gametes .

As with fungi, some algae exhibit heterothallicity (Section 3.1.3).

3.2.4. Division Chlorophyta

The main properties of Chlorophyta are listed in Table. 3.4.

Table 3.4. Systematics and main features of some major groups of algae 1)

1) (An asterisk marks a systematic feature.)

Chlamydomonas (chlamydomonas) is a unicellular mobile algae that lives mainly in stagnant water, i.e. in ponds and ditches, especially if the water is also enriched with soluble nitrogenous compounds, such as runoff from stockyards. The cells of this algae are often found in such huge numbers that the water turns green. Some species live in sea water or in brackish estuaries.

Structure

Chlamydomonas is not at all like a plant, as it actively moves and has pulsating vacuoles. The structure of chlamydomonas is shown in fig. 3.14. The electron micrograph shows typical eukaryotic organelles: the Golgi apparatus, mitochondria, ribosomes, and small vacuoles. In the chloroplasts of many algae, a special structure was revealed - pyrenoid. This is a protein formation, consisting mainly of ribulose bisphosphate carboxylase, an enzyme that fixes carbon dioxide. The pyrenoid is involved in the storage of carbohydrates, such as starch. red eye perceives changes in light intensity, and the cell either moves to where the light intensity is optimal for photosynthesis, or remains in place if the light is sufficient. This response to light is called phototaxis(Section 15.1.2). The chlamydomonas cell moves due to the beating of two flagella and is screwed into the water like a corkscrew, rotating around the longitudinal axis.

Rice. 3.14. A. Chlamydomonas under a light microscope; x 600. B. Scheme of the structure of Chlamydomonas. B. Electron micrograph of Chamydomonas reinhardtii. × 1400

Life cycle

The life cycle of Chlomydomonas is depicted in fig. 3.15. The adult is haploid.

asexual reproduction

Asexual reproduction is carried out with the help of zoospores. The parent cell loses flagella and the cell's protoplast divides into two to four daughter protoplasts (usually four). At the same time, mitotic division of the nucleus occurs; in addition, the chloroplast also divides. The daughter protoplasts develop new cell walls, new eyes, and new flagella. Centrioles (basal bodies) are involved in the formation of new flagella. The cell wall of the parent cell becomes mucilaginous, and the daughter cells, now called zoospores, come out. From each zoospore grows a full-fledged adult Chlamydomonas cell. This process is shown in Fig. 3.16, A.

sexual reproduction

Some species of Chlomydomonas are homothallic, others are heterothallic; wherein different types may be isogamous, anisogamous or oogamous. Reproduction of isogamous species is shown in fig. 3.16, B. During germination, the nucleus of the zygote divides meiotically for the first time, and the haploid state characteristic of adult organisms is restored. Released young cells of Chlomydomonas can be called zoospores until they are fully mature.

In ponds and other bodies of water with stagnant, but clean water one more alga lives - the non-branching filamentous algae Spirogyra. Most species of spirogyra are floating forms, and its threads are slimy and slippery.

Structure

Cylindrical cells of spirogyra are connected end to end and form a thread shown in Fig. 3.17. All cells are identical, and there is no separation of functions between them. A thin layer of cytoplasm lies along the periphery of the cell, and a large vacuole is, as it were, wrapped in strands of cytoplasm. These strands hold the nucleus in the center of the cell. One or more spiral chloroplasts lie in a thin walled layer of the cytoplasm.

Growth and reproduction

The filaments of spirogyra grow intercalary, i.e., due to the division of any of the cells that make up the filament, regardless of where this cell is located. In most plants, the growth zone is limited to the apical region. The nucleus of the spirogyra cell divides mitotically, then a new transverse cell wall is formed from the outgrowths of the side walls. Two daughter cells are obtained, which grow to normal sizes, as a result of which the entire thread increases in length.

As we have already noted (section 3.2.1), asexual reproduction occurs by fragmentation.

Sexual reproduction is carried out in a very specific way, characteristic of filamentous algae: two filaments are located side by side and the opposite cells of both filaments are connected by short tubular outgrowths. The entire contents of the cell behaves like a gamete; this process can be regarded as anisogamous, since, although both gametes are morphologically identical, only one of them is mobile and flows into the other cell through a connecting tube. This process is called conjugation.

3.2.5. Division Phaeophyta

The main features of Phaeophyta are listed in Table. 3.4.

Along the rocky shores of the British coast, various algae from the genus Fucus are often found. They have adapted very well to the rather harsh conditions of the littoral zone, that is, the zone that is alternately exposed at low tide, then again covered with water.

The best known are three species of Fucus, which are most often found near the coast in three different zones at different depths; this phenomenon is called zonal distribution. These algae are categorized according to their ability to withstand exposure to air. We list the main signs by which they can be recognized, and the places on the coast where they can be found:

F. spiralis (these flat algae are washed ashore by the sea) - in highest point high tide. When immersed, the thallus is slightly twisted into a spiral.

F. serratus (what is called ordinary, serrated or serrated algae) - in the middle intertidal zone. The edges of the thallus are serrated.

F. vesiculosus (the so-called bubble algae) - at the highest point of low tide. There are air bubbles that cause buoyancy. On fig. 3.18 you can see the characteristic external signs F. vesiculosus, and in fig. 3.19 shows the main features of its internal structure.

Rice. 3.18. External structure of Fucus vesiculosus. Characteristic features and, in particular, adaptations to environment. fruitful end(receptacle) is a part of the thallus swollen and covered with small swellings (scaphidia or conceptacles), communicating with the external environment only through narrow holes. In female plants, the fruiting ends are dark green, in male plants, orange. air bubbles usually paired and give algae buoyancy. Adventitious branches(sometimes break off; this is one form of vegetative propagation). apex cell represents the growth point where cell division occurs. Edge- this is a rigid formation that performs mechanical functions and, possibly, is involved in the transfer of certain substances. Plate flat and elastic (skinny); greenish-brown color due to the photosynthetic layer close to the surface; covered with mucus, which prevents it from drying out at low tide. The rib together with the plate form a thallus. The rooting part of the thallus (in this case basal disc) is colorless and attaches very strongly to rocks with a thallus, etc. The size of the algae varies up to 1 m or more. Thallus flat and belt-like; the nature of branching is such that resistance to waves is minimized; air bubbles support the thallus near the surface, which promotes photosynthesis. Petiole- this is basically a rib; petiole is flexible and therefore successfully resists waves

In the body of the algae, or thallus, there is some separation of functions between different tissues. This trend is better seen in Phaeophyta than in all other groups of algae. We will look at the adaptations of algae to the environment a little later.

Reproductive organs

Sexual reproduction is oogamous. F. vesiculosus and F. serratus are dioecious, meaning they have both males and females. F. spiralis is a hermaphrodite, which has both male and female reproductive organs on the same plant in the same receptacles - scaphidia, or conceptacles. Reproductive organs develop inside scaphidia on the "fertile" tips of some thalli. Each scaphid has a narrow opening (pore) through which the reproductive organs are subsequently released. Their structure is shown in Fig. 3.19.

Adult plants are diploid, and gametes are formed as a result of meiotic division.

Adaptations to the environment

Before we consider the adaptations of Fucus to the habitat, a few words should be said about the environment itself, which is quite hostile. Being plants of the intertidal zone, various algae in varying degrees exposed to the air during low tide. Therefore, they must have protective devices from drying out. In addition, the temperature changes very sharply when cold sea waves pour into warm puddles left after low tide. Plants must be adapted to another factor, namely, to sudden changes in the salinity of the water, whether it is increased by evaporation from small pools formed after low tide, or decreased during rain. In order to withstand such factors as tides, surf and wave impacts, sufficient mechanical strength is needed. Large waves begin to roll stones, and this can cause very severe damage to plants.

Morphological adaptations (general structure)

Thallus algae is firmly attached to the ground rooted part of the thallus(rhizoids or basal disc) (Fig. 3.18). It binds so strongly to the ground (usually stones) that the algae is extremely difficult to tear off from it. As a rule, the stone does not withstand the first, and not the rooting part of the thallus.

Algae thallus is not continuous, but dissected; it branches dichotomously in the same plane, and this allows you to minimize the resistance of the water column. In addition, it is durable and resilient, but not rigid. The ribs of the thallus are strong and flexible.

The floating algae F. vesiculosus has special air bubbles that keep the thallus at the surface of the water, i.e., under conditions conducive to maximum light capture for photosynthesis.

physiological adaptations

Among the photosynthetic pigments, brown pigment predominates - fucoxanthin. This is one of the adaptations for underwater photosynthesis, since fucoxanthin strongly absorbs blue light, which penetrates much further into the water column than longer wavelengths, such as red ones.

The thallus secretes a lot of mucus, which fills all the internal cavities of the algae and seeps out. Mucus helps to retain water better and prevents dehydration.

The osmotic pressure in cells is much higher than in sea water, so no osmotic loss of water is observed.

Adaptations for sexual reproduction

The release of gametes is synchronized with the tides. During low tide, the thallus dries up, and the reproductive organs are squeezed out of the scaphidia, which are protected from drying out by mucus. During the tide, the walls of the reproductive organs dissolve, releasing gametes. Male gametes are motile and have positive chemotaxis for substances secreted by female gametes.

The development of the zygote occurs immediately after fertilization, minimizing the risk of being swept into the ocean.

3.2.6. Division Euglenophyta

The main features of Euglenophyta are given in Table. 3.4. This department is characterized by signs of both plants and animals, which greatly complicates the classification of organisms belonging to this area. For this reason, both botanists and zoologists usually include them in their systematic schemes. These problems will be discussed later, after the description of the genus Euglena.

Euglena is the most common single-celled algae found in freshwater ponds, ditches, and any other body of water rich in dissolved organic compounds. Like Chlamydomonas, it sometimes reproduces so intensely that the water turns green, because chlorophyll predominates among the pigments of euglena. The structure of euglena is shown in fig. 3.20, where some of its features are noted.

Rice. 3.20. Structure of Euglena gracillis. Channel- the place through which food enters in non-green species; the pellicle is absent here, which allows swallowing small particles. peephole(stigma) is red; involved in the phototaxis reaction. Photoreceptor detects a light source and causes the body to swim in the direction of optimal illumination (phototaxis); the direction of movement can change when the photoreceptor is shaded. Long flagellum used for locomotion; usually directed forward; wave-like movements pass along the flagellum from the base to the tip; the flagellum drags the cell behind it; while moving forward, the cell rotates around its axis, leaving a corkscrew-like trail behind it. Pulsating vacuole surrounded by accessory vacuoles; participates in osmoregulation, pumping out excess water into the reservoir, which entered the cell as a result of osmosis. short flagellum does not participate in locomotion. Paramylon granule is formed by a polymer of glucose, similar to starch and is a storage carbohydrate. pellicle located under plasma membrane; flexible. Chloroplasts contain photosynthetic pigments. AT cytoplasm there are contractile fibers that cause peristaltic waves of cell deformation; this movement is called euglenoid

Euglena does not have a cell wall. Outside, the cell is covered with a plasma membrane, immediately below which is a protein pellicle. The pellicle is quite flexible and this allows the cell to accept different shape. The pellicle completely surrounds the cytoplasm and can be seen as a kind of exoskeleton. It consists of a series of thickened longitudinal strips and microfibrils intertwined. When inside the cytoplasm, tiny fibrils called mionemy, the pellicle strips begin to slide relative to each other, as a result of which the shape of the body changes. This phenomenon is called euglenoid movement. Another, more common for euglena way of locomotion due to the rotation of a long flagellum is shown in fig. 3.20 (consider the ocellus, photoreceptor, and long flagellum) and is described in detail in sec. 17.6.3.

Asexual reproduction occurs through the longitudinal division of the cell in two. Sexual reproduction is not observed.

Food

Green species of Euglena are autotrophic and synthesize all the substances they need from carbon dioxide, water and mineral salts. At the same time, they need to receive vitamins B1 and B12 from outside, which they cannot synthesize themselves. In this, Euglena is no different from animals, although many other algae also have such a need for vitamins.

Several species of Euglena do not have chlorophyll and therefore are neither colored nor capable of photosynthesis (i.e., they are heterotrophic). They feed on the type of saprophytes, digestion occurs outside the cell. When a body of water is polluted, they thrive, as the decaying material is rich in organic compounds. Other colorless forms are able to swallow small particles of food, for which they have a kind of "pharynx", where there is no pellicle. These particles are then digested inside the cell (holozoic nutrition, Section 10.1.1). Food is driven into the pharynx by the movement of flagella. These species are in many ways reminiscent of the simplest Rerapema (Section 4.1.1).

If the green cells of Euglena are kept in the dark for a long time, the chloroplasts disappear and the cells become colorless. If there are enough organic substances in the medium, then the cells can live as saprophytes for a long time. When they are brought to light, chlorophyll reappears.

Problems of taxonomy of Euglena

As we have already said, and as follows from Table. 3.1, Euglena is characterized by features of both plants and animals. One of these animal signs, which we have not yet considered, is the presence in the eye astaxanthin- a pigment characteristic of animals.

The ease with which some euglena can change from green to colorless and vice versa indicates that the permanently colorless species appear to have evolved from the green. If subsequently the colorless forms evolved special adaptations for holozoic feeding, similar to those found in Peranema, then it is quite possible that the ancestors of the protozoa were similar to plants. It should not be forgotten, however, that evolution could also have gone in the opposite direction, since we already discussed at the beginning of this chapter the possibility that plant ancestors could be similar to animals (i.e., heterotrophic eukaryotes).

When deciding whether to place Euglena in the plant kingdom or in the animal kingdom, it must be remembered that Chlamydomonas also has some animal features, and yet it is usually classified as a plant. The main difficulties of taxonomists are connected with the method of nutrition. Apparently, euglena still should be attributed to plants, since the presence of chloroplasts is considered a unique feature inherent only in the plant kingdom. All this, however, once again reminds us how difficult it is to impose on nature an artificial taxonomy invented by people.

3.3. Make a table of plant and animal characters of Euglena. Use the table for this. 3.1, fig. 3.20 and the information above.

3.2.7. Directions of evolution of algae

Even the few examples that we have considered in the previous sections are enough to understand that there are many types of algae, including such unicellular forms as Chlamydomonas, and such relatively large organisms as Fucus, in which the body is differentiated and there is a certain division functions between individual tissues. Some large brown algae even have conductive tissues, although they do not have real conductive tissue - xylem and phloem.

In algae, there is a clear tendency to complicate the process of sexual reproduction from simple isogamy and anisogamy to oogamy. However, one or another trend should be used with a great deal of caution to explain the evolutionary relationships between individual groups of algae. Such relationships have not yet been fully elucidated, and the Chlorophyta (green algae) group from which they are believed to have originated land plants, is very diverse: it has both simple unicellular forms and much more complex ones, and sexual reproduction also varies from isogamy to oogamy.

3.2.8. The value of algae

The role of algae in the biosphere

Current estimates suggest that the ocean accounts for at least half of the world's primary production in terms of fixed carbon. This primary production is formed by algae - the only plants that inhabit the ocean. Given the vast area that the ocean occupies, we should expect that its productivity should be even greater, but we must not forget that photosynthesis is possible only in the surface layers, where light penetrates and where the limiting factor is the availability of nutrients, especially nitrogen and phosphorus.

Algae are very important primary producers (Ch. 12) that start most food chains, including virtually all marine and many freshwater chains. These chains reach fish through zooplankton*, crustaceans, etc. Many microscopic algae are single-celled, and they are the main component of phytoplankton * .

* (Plankton are the smallest plants (phytoplankton) and animals (zooplankton) that swim freely in the surface layers of oceans and lakes. Plankton is of great economic and ecological importance.)

Carbon fixation is only one of the consequences of photosynthesis (Section 9.2). In addition, photosynthesis maintains the level of oxygen in the atmosphere, with at least half of all oxygen produced by algae, and their contribution to this process is much greater than that of terrestrial forests.

Alginic acid, agar and carrageenan

Many useful products are obtained from algae, such as alginic acid, agar and carrageenan. Alginic acid and its derivatives (alginates) are polysaccharides that are extracted from the median lamina and cell walls of brown algae such as Laminaria, Ascophyllum and Macrocystis. Algae are harvested in large quantities in coastal shallow waters; Macrocystis, for example, is harvested off the coast of California. Purified alginates are non-toxic and easily form gels. They are widely used as hardeners and gelling agents for industrial products (for example, in cosmetics - for the manufacture of hand creams); as emulsifiers - for the preparation of ice cream; as jelly-forming substances - in the confectionery industry; in the manufacture of varnishes, paints and medicines; to obtain glazed ceramic dishes.

agar- a polysaccharide that is obtained from red algae. It forms the same gels as alginates, but is perhaps better known as a very convenient medium for growing bacteria and fungi. For this purpose, a dilute agar solution is prepared, then various nutrients are added to it, sterilized and allowed to solidify, obtaining a jelly-like mass. In addition, agar is used for the same purposes as alginates.

Carrageenan (carrageenan) is another cell wall polysaccharide that is derived primarily from the red algae Chondrus crispus. In its chemical structure, it is very similar to agar and is used for the same purposes.

Diatomaceous earth (kieselguhr)

Algae belonging to the department Bacillariophyta are mostly unicellular; they are called diatoms. These algae are characterized by a special structure of the cell wall, which contains silicon. After cell death, the remnants of diatoms fall to the bottom of the seas and lakes, and gradually large deposits accumulate there. Thus formed "diatomaceous earth" contains a lot (up to 90%) of silicon. After proper purification, this "earth" can be used as an excellent filter material (for example, in the production of sugar or to clarify beer), as a filler in the manufacture of paints or paper, and as an insulating material capable of withstanding sudden changes in temperature.

Fertilizer

On farms located near the coast, large algae (red and brown) are traditionally used as fertilizers, although on a small scale. Algae are rich in potassium, but they contain much less nitrogen and phosphorus than in simple manure. Therefore, their fertilizing effect is not very great. A more significant role is played by free-living blue-green algae, which are very important nitrogen fixers and are quite common in the soil (section 9.11.1).

food products

Some seaweed is served directly to the table, especially on Far East. Considered a delicacy, the red algae Porphyra and the large brown algae Laminaria are commonly eaten raw or used in various dishes. In South Wales, Porphyra is placed in one of traditional dishes, for the preparation of which boiled seaweed is mixed with oatmeal and then it is all stewed in oil. In the search for new food sources, much attention has been paid to the industrial cultivation of algae. However, very few algae are suitable for obtaining new food products, and so far any significant progress in this area has been achieved in the cultivation of bacteria and fungi. Of the blue-green algae, Spirulina is considered promising.

Cleaning of drains

Algae make a certain contribution to the work of microorganisms in wastewater treatment, since wastewater contains nutrients not only for bacteria, fungi and protozoa, but also for microscopic green algae. They are especially useful in open "oxidation ponds", which are widely used in tropical and subtropical countries. Open ponds with a depth of 1 to 1.5 m are filled with untreated wastewater. In the process of photosynthesis, algae release oxygen and thus ensure the vital activity of other aerobic microorganisms growing in wastewater. From time to time, algae are harvested and processed for livestock feed.

Scientific research

Unicellular algae have all the characteristic features of typical plants, so they are an ideal material for scientific research, since, firstly, they can be grown in large numbers under strictly defined conditions, and, secondly, this does not require a lot of space. An example of such algae is Chlorella, which rightfully holds a place of honor in photosynthesis research (Section 9.4.3). Algae are also used in the study of ion absorption. They were also of great use in pioneering studies of the structure of the cell wall and flagella.

Harm caused by algae

Under certain conditions, algae "bloom", that is, they accumulate in large quantities in the water. "Flowering" is observed when enough warm weather when there are a lot of nutrients in the water. Such a situation is very often artificially created by man when industrial effluents are dumped into the water or when fertilizers from the fields get into rivers and lakes. As a result, explosive reproduction of primary producers (algae) begins, and in violation of all the laws of nature, they begin to die off before they have time to be eaten. With the subsequent decomposition of the residues, an equally intensive reproduction of aerobic bacteria occurs and the water is completely deprived of oxygen. All this happens very quickly, and because of the lack of oxygen, fish and other animals and plants begin to die. The increase in the concentration of nutrients in the water that starts this whole process is called eutrophication reservoir, and if it occurs quickly, then we can assume that this is another form of environmental pollution.

Toxins formed during the "bloom" of water, especially during the reproduction of blue-green algae, increase the death of animals. Such bursts of algae are a serious problem for fish farms, especially where the intensive removal of fertilizers to the fields further increases eutrophication. Similar complications arise with the "bloom" of water in the ocean. In addition, toxins, accumulating in the body of mollusks and crustaceans that feed on algae, and then entering the human body, cause various poisoning and paralysis in him.

Algae is also associated with many difficulties in storing drinking water in reserve tanks when it becomes contaminated with algae waste products or when algae begin to grow on sand filters, completely clogging them.

3.4. The difficulties we have just discussed are more likely to occur in reservoirs located in lowlands. Explain why this is the way it should be.

3.5. Unlike many fungi and bacteria, algae do not cause any disease. What is it connected with?

The manual is written in accordance with the requirements of the Federal State Educational Standard of Higher Professional Education in the direction of "Pedagogical Education" and complements the knowledge of students in the theoretical part of the course "Botany" (systematics of plants and fungi). The material of the manual can be used by students for both independent work, and for work in the classroom under the guidance of a teacher.

* * *

The following excerpt from the book Botany. Plant Systematics: a textbook (S. K. Pyatunina, 2013) provided by our book partner - the company LitRes.

Seaweed (algae)

A large and diverse group of lower thallus plants whose primary habitat is water. Algae unite several independent and, in all likelihood, independently evolved departments. Representatives of the departments differ in the set of pigments, details of the fine structure of chromatophores, in the products of photosynthesis that accumulate in the cell (reserve substances), and in the structure of the flagellar apparatus. Lower plants are unicellular, colonial or coenobial and multicellular organisms. Colonies are called cenobia, in which the number of cells is determined in the early stages of development and does not change until the next stage of reproduction (reproduction). The growth of coenobia occurs due to an increase in the size of cells, and not their number. There are the following types of morphological organization of the thallus:

1. Monadic- cells that actively move with the help of flagella.

2. coccoid- immobile cells.

3. rhizopodial (amoeboid)- vegetative cells are not covered with membranes and can develop cytoplasmic processes - rhizopodia.

4. palmelloid, or capsal, the type of organization is represented by immobile cells immersed in a common mucus.

5. filamentous- cells connected in threads, simple or branched.

6. heterotrichous, or multifilamentous,- a complicated version of the filamentous structure, which is characterized by two systems of threads: creeping along the substrate and vertical threads extending from them.

7. lamellar- thalli in the form of plates.

8. Siphonal- thalli, often large, formally represent one cell, usually with a large number of nuclei.

9. siphonocladal the organization is represented by multinuclear cells connected in filamentous or other forms of multicellular thalli. At the first stages of thallus formation, it has a siphonal type of structure.

Algae can reproduce in three ways: vegetatively, asexually and sexually. Vegetative propagation consists in separating a part of the vegetative thallus from the whole plant, giving rise to a new thallus. Asexual reproduction is carried out with the help of specialized cells - dispute, produced in sporangia. Spores are mobile (zoospores) or motionless (aplanospores). They may be identical in shape to the parent thalli. (autospores unicellular algae) or differ sharply from them (unicellular spores of multicellular algae).

Sexual reproduction in algae is extremely diverse. The simplest forms of the sexual process - the fusion of morphologically indistinguishable vegetative individuals - hologamy and conjugation. In a significant part of algae, the formation of specialized germ cells - gametes. The following behavior of hemets is distinguished:

1. Isogamy - fusion of gametes of the same size and shape.

2. Heterogamy - both types of copulating gametes have flagella, but the female is larger and less mobile than the male.

3. Oogamy - fusion of an immobile female egg and a mobile male cell. Copulate gametes that have arisen on the same individual (homothallism) or on different individuals (heterotallism). Heterotallism is observed in any form of the sexual process. In isogamous forms, gametes with morphological identity turn out to be physiologically different and are designated by the conventional signs "+" and "-". Male gametes that have flagella are called spermatozoa, not having flagella, but able to move with the help of amoeboid movements are called spermatozoa. As a result of the sexual process, a diploid cell is formed - zygote.

Life cycle, or algae reproduction cycle, includes vegetative growth, asexual sporulation, sexual process, resting stages. The ratio of diploid and haploid phases in the life cycle of algae is not the same. In some cases, the germination of the zygote is accompanied by a reduction division (meiosis) of the zygote. (zygotic reduction), while developing plants are haploid. In many green algae, the zygote is the only diploid stage in the development cycle; the entire vegetative phase passes in the haploid state. This life cycle is called monohaplobiont. In some other algae, on the contrary, the entire vegetative phase is diploid, the haploid phase is represented only by gametes, before the formation of which the reduction division of the nucleus occurs. (gametic reduction), life cycle - monodiplobiontic. In still others, the reduction division of the nucleus precedes the formation of spores that develop on diploid thalli. (sporic reduction). They grow into haploid sexually reproducing plants. (gametophytes). After the fusion of gametes, the zygote develops into a diploid plant, bearing organs of asexual reproduction ( sporophytes). Thus, these algae have an alternation of generations (generations): diploid and haploid. Life cycle - haploid-diploid. Both generations may be morphologically the same ( isomorphic change of generations) or drastically different in appearance (heteromorphic change of generations).

In practical classes, they study the departments: green (Chlorophyta), diatoms (Bacillariophyta or Diatomeae), brown (Phaeophyta), red (Rhodophyta) algae.

Department of Green Algae (Chlorophyta)

The Department of Green Algae is the largest in terms of the number of species (up to 20,000 species) and morphologically diverse department of algae. There are also microscopic small, unicellular forms (monadic and coccoid) and quite complexly arranged filamentous, heterotrichous, siphonal, siphonocladal and lamellar forms, reaching several tens of centimeters. The area of ​​distribution of green algae is also extensive (they are found all over the globe) and their ecological amplitude is wide. They live in fresh and marine waters, some live out of water. But with all the diversity, green algae have a number of common features:

1) pigment composition: chlorophyll a and in, carotenoids and xanthophylls;

2) the main reserve product of a carbohydrate nature, starch, is deposited in the chromatophore around the pyrenoid;

3) photosensitive eye - stigma, located in the stroma of the chromatophore;

4) thylakoids bearing pigments tend to stack;

5) flagella are isomorphic (same in structure) and isocontoid (equal in length).

Class Actually green, or equal flagella, algae (Chlorophyceae, Isocantae)

Representatives of this class are characterized by asexual reproduction with the help of immobile aplanospores or mobile zoospores with two to four, less often many isocont and isomorphic flagella. Sexual processes - chologamy or copulation of gametes - isogamy, heterogamy, oogamy. The zygote usually goes through a dormant state and germinates when favorable conditions occur, and its diploid nucleus immediately divides by reduction. In accordance with the steps of morphological differentiation of the thallus, the class is divided into orders.

Order Volvox (Volvacales)

The order includes unicellular, colonial and coenobial algae equipped with flagella, that is, a monadic organization.

Genus Chlamydomonas (Chlamydomonas)

Chlamydomonas is an extensive genus of about 500 species, widely distributed in nature. Its species can be found in shallow, well-heated reservoirs, puddles, ditches. With mass development, it causes flowering of water, especially in reservoirs polluted with organic substances. The thallus of chlamydomonas is unicellular, of a monadic organization, that is, being in an active state, chlamydomonas quickly move with the help of two equal flagella attached to the anterior end of the body. The phase of active movement is replaced by a state of rest. This is the so-called palmelle-like stage, when the cells lose their flagella, their membranes become strongly mucilaginous and form aggregations of Chlamydomonas cells immersed in the common mucus. In this form, chlamydomonas cells multiply by division. Getting into favorable conditions of existence, chlamydomonas again produce flagella and move on to active movement.

Chlamydomonas has a cellulose-pectin cell membrane, a cup-shaped chromatophore with one or more pyrenoids located in the lower part, and a light-sensitive eye (stigma) in the upper part. The nucleus is located in the deepening of the chromatophore, there is a pair of pulsating vacuoles. Asexual reproduction by zoospores occurs in favorable habitat conditions. Each Chlamydomonas can potentially reproduce both vegetatively and asexually, as well as participate in the sexual process. During asexual reproduction, the protoplast divides into 4 or 8 parts, zoospores are formed. The sexual process in most species is isogamous. Gametes are formed in the same way as zoospores, but in larger numbers (32 or 64). The zygote is well adapted to endure adverse conditions. Its germination is accompanied by reduction division. The development cycle of chlamydomonas is monohaplobiont.

Rod Volvox (Volvox)

The genus Volvox is a colonial or coenobial algae. A small genus of Volvox lives in clean standing water, ponds and small lakes. This is the most highly organized representative of the Volvox order. It is a large ball, reaching 2–3 mm in diameter, covered with a thin layer of mucus (involucrum), under which biflagellated cells are located in one layer along the periphery of the ball. Their number ranges from 500 to 60,000. The inner cavity of the ball is occupied by liquid mucus. The cells of the colony are similar in structure to the cells of chlamydomonas. But the shell of each cell is strongly mucus, so the protoplasts of neighboring cells are distant from each other and the cytoplasmic processes penetrate the thickness of the mucus membrane. Plasmodesmata are formed at the points of contact.

In asexual reproduction, 8-10 cells are involved, located in the back, relative to the direction of movement, part of the sphere. These are gonidia. Among others, these cells are distinguished by larger sizes. When they divide, a flat 16-cell plate is first formed (gonic stage), further division leads to the formation of an open sphere with a small open hole directed towards the outer surface of the parent colony. The forming cells of the new organism are turned with their flagella into the sphere. The normal orientation of the cells (with the anterior ends directed outward) is achieved by completely turning the open sphere inside out, only after that its opening closes. Reproductive cells differentiate very early, so that not only daughter colonies, but granddaughter colonies can be observed inside the maternal organism. Young colonies are released after the destruction of the mother colony.

Cells that serve for sexual reproduction are oogonia and antheridia. Dark green oogonia are much larger than other cells and lack flagella. One large egg develops in the oogonium. Antheridia form packets of spermatozoa. The sexual process in Volvox is oogamous. There are bisexual and dioecious species, as well as homo- and heterothallic clones. A resting zygote is formed, which germinates as a young daughter colony after the reduction division of diploid nuclei. The development cycle is monohaplobiont.

Objects: r. chlamydomonas, r. volvox.

Progress

1. Consider chlamydomonas first at low magnification (m. magnified), then in more detail at high magnification (b. magnified), study immobile individuals, observe the movement of chlamydomonas.

2. Make two drawings:

a) the appearance of chlamydomonas. Designate the shell, chromatophore;

b) a diagram of the structure of the chlamydomonas cell, using the table. Designate the membrane, cytoplasm, nucleus, chromatophore, ocellus (stigma), pyrenoid, flagella, pulsating vacuoles.

3. Consider at m. and sketch spherical coenobia of volvox with daughter colonies from the preparation.

4. Make a schematic drawing using the table, reflecting the structural features of the coenobia. Name the protoplasts, cytoplasmic processes, plasmodesmata, flagella, oogonia, antheridia.

Order Chlorococcal (Chlorococcales)

The order includes unicellular and coenobial forms with coccoid cell organization.

Genus Chlorococcus (Chlorococcus)

The genus Chlorococcus contains 38 species and is found in a variety of habitats: in water, both in plankton and in benthos; in the soil, as well as on the bark of trees, on old wooden buildings. Chlorococcus is a part of lichens.

It is a unicellular coccoid algae, immobile in the vegetative state. The cells have a cupped chromatophore with a pyrenoid, but lack flagella, ocelli, and pulsating vacuoles. The nucleus is located in the recess of the chromatophore. In old individuals, several nuclei can be observed, the cells are covered with a thick cellulose membrane.

Chlorococcus reproduces asexually with the help of elongated biflagellate zoospores. The protoplast of the mother cell divides and forms from 8 to 32 zoospores, which are released after the destruction of the wall of the mother cell. The period of active movement is short; after swimming for some time, zoospores lose their flagella, dress in a shell, grow, reaching sizes characteristic of a particular species. The sexual process is isogamous. The development cycle is monohaplobiont.

Genus Hydrodition (Hydrodiction)

Hydrodition is a small but widespread genus. It is found in backwaters of rivers, ponds and other stagnant water bodies enriched with nitrogen. This is a macroscopic coenobial alga, composed of a large number (up to 20,000) of cells. Old specimens reach a meter in length, and their cells are up to one and a half centimeters.

Hydrodiction looks like a closed network, consisting of 5-6-coal cells formed by giant cells connected at their ends. Adult reticulum cells contain one giant vacuole, the cytoplasm is parietal and contains a reticulate chromatophore with numerous pyrenoids and a large number of small nuclei. The shell is cellulose. Each cell performs all the functions of the body (nutrition and reproduction).

Reproduction of the water mesh is asexual and sexual. Cells that have already reached a sufficiently large size (0.2 mm) begin asexual reproduction. In the protoplast, such a number of zoospores is formed that is characteristic of this type of reticulum. Zoospores do not leave the mother cell, but move inside the cell for some time.

Then the flagella are shed and folded into a young mesh, sticking together with each other in those places where the strands of microtubules pass. The cells of the young reticulum are mononuclear, with a lamellar chromatophore bearing one pyrenoid. For some time, the young mesh lives under the shell of the mother cell, but its size rapidly increases, the cells are elongated. In the end, the shell of the mother cell is destroyed, and the reticulum begins to live independently.

Sexual reproduction is isogamous, gametes are formed more than zoospores, and they are much smaller. The zygote is stained with hematochrome brick red. After a dormant period, the zygote divides by reduction and germinates into four large zoospores. They are inactive, soon lose their flagella and again become covered with a thick, but already sculptural shell, turning into the so-called polyhedron Polyhedra, the shells of which have processes, and the contents are rich in fatty inclusions, apparently, are important for the distribution of algae. Polyhedra can tolerate desiccation well and are thus the second dormant stage in the water network development cycle.

Genus Chlorella (Chlorella)

Chlorella is a very widespread algae. In nature, it is found in plankton and benthos of various water bodies, on the soil, participates in the formation of the body of lichens, and also lives in symbiosis with small animals, forming the so-called zoochlorella. It is one of the cultivated algae. Thanks to high speed reproduction, chlorella gives a large yield of biomass.

Chlorella is a single-celled spherical coccoid algae. The protoplast contains a bell-shaped chromatophore with a large depression. In the cavity of the chromatophore, a nucleus can be found. Chlorella reproduces only asexually by autospores. The sexual process is unknown. The development cycle is asexual, monohaplobiont.

Objects: r. chlorococcus, r. water mesh, r. chlorella.

Progress

1. Consider at b. led away. and draw chlorococcus. Designate a thick shell (an adaptation to an aerophilic lifestyle), a cup-shaped chromatophore.

2. Consider at m. a fragment of the coenobium of the water mesh and draw, showing 5-6-angled cells that form the coenobium. Designate the cell of coenobia, chromatophores.

3. Consider at b. led away. and draw a cell of a coenobium with a young coenobium inside the cell. Designate the shell of the mother cell, the young coenobium.

4. Sketch chlorella at b. led away. Name the thick shell, chromatophore.

Order Ulotrix (Ulothrichales)

The order combines algae that have a thallus in the form of an unbranched thread, composed of mononuclear cells, less often a lamellar or tubular thallus.

Rod Ulotrix (Ulothrix)

Ulothrix is ​​a fairly large genus, found in fresh and slightly brackish water bodies, preferring clean running water. In the coastal zone of rivers and streams, especially in areas with a suitable climate, Ulothrix zonata can be found. Ulothrix is ​​a benthic, attached algae that forms aggregations on coastal rocks.

Ulothrix is ​​a multicellular filamentous unbranched algae. All cells, with the exception of the basal, which serves for attachment, are of the same type. They are covered with a thin, sometimes mucilaginous, cellulose membrane. The chromatophore is parietal in the form of a closed or open belt with a large number of pyrenoids. There is only one nucleus in the cells. The number of cells in the filaments is indeterminate, since the cells in the upper parts are constantly dividing in the same plane. Ulothrix reproduces vegetatively (by fragmentation of the thread), asexually and sexually. Asexual reproduction is carried out by zoospores equipped with four isocont and isomorphic flagella. Zoospores, germinating, form ulotrix filaments. Any but the basal cell of the filament can potentially become a zoosporangium. Ulothrix forms biflagellated isogametes. After fusion, a planosygote is formed (a mobile cell with four flagella), which then loses flagella and differentiates into a unicellular peculiar sporophyte - an expanded body covered with a thick shell on thin leg. The zygote-sporophyte stays in such a resting state for some time, and then, after reduction division, 4-16 zoospores are formed in it. Such a life cycle is characteristic of Ulothrix zonata. In some species, the zygote grows into a diploid filament. Thus, the cycle of development in Ulothrix zonata is with a heteromorphic change of a multicellular filamentous haploid sporogametophyte and a unicellular diploid sporophyte.

Rod Ulva (Ulva)

The genus Ulva is known as "Sea Lettuce" and is widely distributed but prefers shallow waters. Ulva is a seaweed, but it tolerates desalination well. It lives in estuaries, shallow estuaries, marshes; well tolerates, and partly prefers waters with significant organic pollution. The local population uses it for food, but the ulva has no commercial value.

The ulva thallus is multicellular, lamellar, consists of two layers of cells, the edges of the plate are corrugated due to more intense cell divisions in the marginal, compared with the median, zones. At the base, the plate narrows into a short petiole with a sole, with which it is attached to a solid substrate. Cell differentiation in the ulva thallus is low. There are no special reproductive organs. Potentially, each cell can become a sporangium in the diploid generation or a gametangium in the haploid one. Some cells have tubular outgrowths descending along the central part of the thallus.

Asexual reproduction is carried out by four-flagellated zoospores, which are formed on diploid plants after reduction division. Zoospores germinate into a single-row non-branching thread, but even before the start of division, polarization is detected in the zoospore that has lost flagella and settled on the ground. The upper end is thicker, while the lower end is thin and elongated, from which attachment structures are subsequently formed. The sexual process is iso- or heterogamous, the gametes are biflagellated. The cycle of development is haplodiplobiont with an isomorphic change of generations.

Objects: r. ulotrix, r. ulva.

Progress

1. Consider at b. led away. and draw a section of the ulotrix filament, pay attention to the structure of the chromophore. Label the cells of the thallus: cell membrane, chromatophore, pyrenoids.

2. Sketch the appearance of the ulva thallus using a wet preparation.

Chaetophore order (Chaetophorales)

The order includes multicellular filamentous forms of the heterotrichous type with thallus differentiation into a horizontal, extended along the substrate, and a vertical system of filaments.

Rod Draparnaldia (Draparnaldia)

Species of this genus are demanding on cleanliness and aeration of reservoirs and prefer fast-flowing rivers and streams. They grow en masse at fairly significant depths (10 m), forming whole thickets there. Draparnaldia benthic is an attached algae of a filamentous heterotrichous structure. It has long (unlimited growth) weakly branching filaments with a girdle-shaped chromatophore with jagged edges. The chromatophore in such branches is small relative to the total volume of the cell, so the cells of the main filaments are pale. Bunches of short highly branched branches of limited growth depart from these threads in whorls, these are assimilators. The chromatophores in them are parietal, large; green cells. Each short thread ends with a colorless long hair. The reproductive organs are placed among the assimilators. Asexual reproduction by four flagellar zoospores. The sexual process is isogamy or heterogamy. The development cycle is monohaplobiont.

Genus Trentepolia (Trentepohlia)

Trentepolia is an aerophilic terrestrial alga, well adapted to the lack of moisture. She settles on the bark of trees, stones, wooden buildings. Especially many species of this genus are found in humid tropical and subtropical regions, where trentepolia often leads an epiphytic lifestyle. Trentepolia is easy to recognize among other terrestrial algae due to hematochrome, an oil-soluble carotenoid that gives it a brick red or yellow. The thallus of trentepolia is filamentous, heterotrichous. The filaments that creep along the substrate consist of rounded or oval cells covered with a thick layered membrane. They are connected to each other by pores with plasmodesmata, but, nevertheless, the creeping filaments easily disintegrate into short fragments or individual cells. These fragments and cells in the dry state are dispersed and carried by the wind. Thus, trentepolia has a fairly effective mechanism of vegetative reproduction, which is especially important in conditions of water deficiency. The cells contain several disc-shaped or ribbon chromatophores devoid of pyrenoids and a large number of nuclei, especially in old cells. In addition to the horizontal, there is a system of vertical threads, consisting of more elongated cells. Both horizontal and vertical filaments branch profusely due to the division of apical cells; layered caps form on the latter.

Asexual reproduction occurs by two- or four-flagellated zoospores, which are formed in special apical cells - sporangia, sitting on tubular cells - legs. The sporangia are detached and carried in their entirety by air currents. Zoospores are formed only if the sporangium is in the water. Then the multinuclear content very quickly, in a few minutes, breaks up into single-nuclear sections, and zoospores are produced. Gametangia also differ morphologically from vegetative cells, but are located mainly on creeping filaments. Unlike sporangia, globular gametangia do not have legs. Gametangia are also carried by air currents. Once in the water, they germinate with biflagellate isogametes. However, copulation is rare, and gametes develop parthenogenetically (without fertilization). In the case of the formation of zygotes, they germinate as zoospores after a dormant period. The development cycle is monohaplobiont.

Objects: r. draparnaldia, r. trentepoly.

Progress

1. Consider at m. and draw a section of the heterotrichal filamentous thalom of Draparnaldia, note the structural features of the “stem” filaments and assimilators, show the difference in the structure of chromatophores in the cells of the axial filament and in the cells of the lateral branches. Designate the axial thread, assimilator threads.

2. Consider at b. led away. and draw the cell of the axial thread and the cell of the assimilator thread. Label the cell wall, the chromatophore.

3. Consider at b. led away. and sketch a section of the trentepoly thread. Designate the layered membrane, reserve substances (in the form of oil drops stained with hematochrome), disk-shaped chromatophores.

Order Cladophoraceae (Cladophorales)

The order includes non-cellular algae, filamentous branched, divided by transverse partitions into unequal segments, each of which contains many nuclei. Transverse partitions arise independently of nuclear fission.

Genus Cladophora (Cladophora)

Cladophora is a very large and widespread genus of mainly marine and partly freshwater algae. About 150 species have been described. It occurs in shallow waters in the surf zone, on rocks protruding into the sea, in lagoons, ponds, lakes. Young plants are attached to the ground or to various underwater objects, but later break off and swim, forming large clusters or hard mud; as well as large (10–15 cm in diameter) globular clusters. The thallus is highly branched, with a siphon-clad structure. The segments formed by the transverse partitions are not cells in the true sense. The formation of transverse septa is qualitatively different from cytokinesis and is not associated with nuclear fission. The segments are unequal in size and contain a different number of cores. The mesh chromatophore is also formed by contact and fusion of initially free chloroplasts. The outer shell is thick, cellulose, never mucus, so Cladophora mud is tough and not slippery.

Reproduction is asexual and sexual. Any segment of the alga can become zoosporangium or gametangium. Tetraflagellated zoospores emerge from the sporangium through a pore and germinate first into a vesicular body devoid of septa (siphonal stage), later transverse septa appear and branching of filamentous structures occurs. The sexual process is isogamous. The zygote grows into a diploid plant. In most species of cladophores living in the seas, an isomorphic change of generations, in which case zoospores are formed after reduction division (meiozoospores), but in freshwater species a monodiplobiont cycle was noted, when the reduction division precedes the formation of gametes.

Objects: r. cladophora.

Progress

Consider at b. led away. and draw a section of the branching thallus of the cladophora with zoosporangia. Designate thallus cells, unicellular zoosporangia.

Class Conjugates (Conjugatophyceae)

Representatives of this class have a special type of sexual process - conjugation, there are no flagellar stages, there is no asexual reproduction by spores.

Zignemov order (Zygnematales)

Order Zignemovye - filamentous unbranched multicellular algae, their shell is mucilaginous, and therefore they are slippery to the touch. The zygote germinates as one seedling, the other three nuclei formed in the process of reduction division die off.

Genus Spirogyra (Spirogyra)

The genus Spirogyra is one of the largest and most widespread around the globe: it is found even in Antarctica. A rare ditch, puddle, pond or lake is devoid of mucous to the touch, floating on the surface of mud. The spirogyra thallus is filamentous, unbranched, all cells in the filament are equivalent and of the same type. The cell has one or more parietal, spiral, ribbon-like chromatophores, with a large number of pyrenoids located along the longitudinal axis. The edges of the chromatophore are uneven. The cell has one or more vacuoles with cell sap. In the first case, the cytoplasm occupies a lean position. In the presence of several vacuoles, in addition to the parietal layer of the cytoplasm, there are cytoplasmic cords and a central cytoplasmic sac, in which there is a large, clearly visible without color, nucleus. The inner layer of the cell membrane is cellulose, the outer layer is pectin, which provides mucus and the formation of a gelatinous cover, which gives the threads a silkiness. In spirogyra, living in reservoirs with a strong current, various kinds of rhizoids are produced that hold the algae in place. Spirogyra, like other conjugates, does not have a flagellar stage in the development cycle and does not form spores. It reproduces either by fragmentation of threads vegetatively or sexually. During conjugation, numerous zygotes are formed, which, after a dormant period, germinate with one thread. Of the four haploid nuclei formed in the process of reduction fission, three small ones die off, and one large viable nucleus remains. All the nutrients accumulated in the zygote go to the formation of one seedling. Zygotes are well adapted to endure adverse conditions. They are covered with a thick three-layer sculpted shell. The structure of the zygote shell is an important taxonomic feature.

Objects: r. spirogyra.

Progress

Consider at m. and sketch the appearance of the multicellular thallus of Spirogyra. Label the thallus cell.

1. Consider at b. led away. and draw a spirogyra cell. Name the cell membrane, chromatophore, pyrenoids,

nucleus, strands of cytoplasm.

2. Observe and draw the different stages of the conjugation process.

Designate the stages: formation of conjugative processes, contraction and overflow of the protoplast, formation of the zygote.

Order Desmidia (Desmidiales)

Order Desmidia - unicellular organisms or filamentous colonies. The cell consists of two equal halves - semi-cells. During vegetative propagation, each semi-cell completes the construction of the second half.

Rod Closterium (closterium)

Klosterium is a freshwater benthic algae that requires good lighting, it lives in small reservoirs, ponds, quiet backwaters of rivers and in fouling of underwater objects. With mass development, mucous accumulations are formed. Closterium loves clean water, but tolerates organic pollution, and is sometimes found in wastewater. This is a unicellular form, its sickle-shaped body consists of two symmetrical halves - semi-cells. The nucleus is located in the center, in the cytoplasmic sac. The closterium does not have an external constriction characteristic of other desmid algae, but the internal structure corresponds to the features of representatives of this order. Closterium has two identical axial chromatophores, a peculiar structure. Several plates extend radially from the central rod so that the chromatophore looks like a multi-beam star in a cross section. Large pyrenoids are located along the shaft or randomly scattered at the base. The base of the chromatophore, facing the center of the cell, is wide; at the ends of the cell, the chromatophore narrows conically. At the poles of the cell there are two small vacuoles with cell sap, in which small crystals of gypsum are immersed, which are in constant motion (Brownian motion), and special mucous bodies. The three-layer shell of the closterium is permeated with numerous conical pores. Particularly large pores are located at the ends of the cells. These pores secrete mucus, thanks to which the alga moves slowly. While one end of the body is attached to the substrate, the other end oscillates. The algae is then attached to the substrate with the other end. So tumbling, the closterium moves towards the light source.

Closterium reproduction is vegetative. Cells divide transversely. Each daughter cell receives half of the mother cell with one chromatophore. The second half, that is, the half-cell, is being completed anew. First, the young semi-cell does not have a chloroplast, and only then the chromatophore of the old semi-cell divides, and one half of it passes into a new semi-cell. Thus, each individual of the closterium consists of two halves of different ages: one is older and the other is younger. The sexual process is the conjugation of two individuals immersed in a common mucus. The zygote is covered with a thick layered membrane and is well adapted to endure adverse conditions. All winter the zygotes are at rest, and for a long time the nuclei remain unfused. From the zygote, two young closteriums are formed, each receiving two haploid meiotic nuclei. One, small, soon degenerates. The second one becomes the nucleus of a new individual. The development cycle is monohaplobiont.

Objects: r. closterium.

Progress

1. Consider the closterium at m. and watch it move.

2. Examine the closterium cell at b. led away. and draw it. Designate the cell membrane, nucleus, chromatophores, pyrenoids, terminal vacuoles with gypsum crystals.

Questions and tasks

1. List the main types of morphological organization in green algae. Describe each type. Give examples.

2. What signs are typical for representatives of the green algae department?

3. What classes are the department of green algae divided into? What is the difference between representatives of each class?

4. What are colonies and coenobia in green algae? Give examples of colonial and coenobial green algae. What is the difference between colonial and multicellular organisms?

5. How does vegetative reproduction occur in green algae? Give examples.

6. How does asexual reproduction occur in green algae? Give examples.

7. What sexual processes are characteristic of green algae? Give examples.

8. Sketch schematically the life cycle of chlamydomonda, ulotrix, ulva, spirogyra. Sign on the diagram which generation is a sporophyte and which is a gametophyte, a set of chromosomes (haploid or diploid) for each generation and cells used for reproduction, the type of reduction division and the sexual process. Indicate the type characteristic of these algae life cycle.

9. Fill in the table:

Comparative characteristics classes and orders

10. Describe the role of green algae in the life of water bodies. Give examples of green algae that lead a terrestrial existence.

Department of Diatoms (Bacillariophyta, Diatomae)

An extensive department of unicellular and colonial organisms, uniting more than 10,000 species. Diatom cells are covered with a silica shell, consisting of two halves that fit on top of each other, like a lid on a box. The larger half is the epithecus and the smaller half is the hypotheca. Each half consists of a sash (bottom) and a girdle ring (girdle) soldered to it. Moreover, the belt of the epithecus is superimposed on the belt of the hypotheca. Under the shell is a pectin shell. Diatoms belong to the group of brown-colored algae, which are characterized by the presence of chlorophylls. a and With, masked by the yellow pigment fucoxanthin. The reserve product of carbohydrate nature is chrysolaminarin. Monadic cells are spermatozoa with one pinnate flagellum. Diatoms reproduce vegetatively, by longitudinal cell division with the completion of one valve - hypotheca. Sexual processes - conjugation and oogamy. After the sexual process, a zygote is formed that has the ability to grow (auxospore). Diatoms live in a diploid state and only their gametes are haploid.

Class Centric (Centrophyceae)

The Centric class combines algae with a radially symmetrical shell and the absence of a suture-nodular apparatus. All centric algae are immobile. The sexual process is oogamy.

Rod Melozira (Melosira)

Melozira is a filamentous colonial alga, consisting of the same type of cylindrical cells, interconnected by the contact of small spines located on the rounded surfaces of the valves. The shell of the melozira has wide belts, therefore, most often the algae is viewed from its lateral surface. The cells have several lobed chromatophores located along the wall, the center of the cell is occupied by a large vacuole with cell sap.

Melozira does not have a suture-nodal structure and therefore is immobile.

Reproduces by division and sexually. The sexual process is oogamy. In some cells, after reduction division, one egg is formed, in others - four spermatozoa with one flagellum. The zygote is covered with a thin, well extensible pectin membrane. Intensively growing zygotes are called auxospores. Since cells crushed after repeated divisions participate in the sexual process, the auxospore restores their original volume. Having reached a certain size, the auxospore develops its own shell. The developmental cycle of Melosyra is monodiplobiont.

Objects: r. melozira.

Progress

1. Examine the site of the Melosyra colony at b. led away. and sketch the algae from the side of the girdle and from the side of the sash. Label the colony cell, epithecus, hypotheca.

2. Locate and draw the auxospore.

Class Pennate (Pennatophyceae)

The Pennate class includes algae with bilateral shell symmetry, having a suture-nodular apparatus, and have the ability to move. The sexual process is conjugation.

Genus Pinnularia (Pinnularia)

The genus Pinnularia includes more than 150 species. It lives in fresh, lime-poor water bodies. Leads a benthic way of life at the bottom or in fouling of underwater objects. Pinnularia, like other diatoms, is of great importance as a food base for small animals and is the initial link in food chains in aquatic ecosystems. This is a unicellular algae with a suture-nodular structure and, as a result, is mobile. Among other unicellular diatoms, pinnularia is large and therefore convenient for study. From the girdle, the shell has a rectangular outline, and the valves are from linear to elliptical. The ends of the valves are mostly rounded, but may be attenuated and capitate. Nodules and two s-shaped slit-like openings (suture) extending from the peripheral nodules to the central one are clearly visible in the center and at the ends of the valve. Along the edges of the sash is clearly visible, especially on empty shells, a clear pattern of parallel partitions - sept, not reaching the seam. Pinnularia cells are mononuclear with two lamellar chromatophores, with curved edges. The wide flat side of the chromatophore faces the side of the girdle, and with its edges it goes to the side of the valve. Living active cells of Pinnularia are colored yellowish-brown, as fucoxanthin masks green pigments, but in dying cells, fucoxanthin is washed out, and the chromatophore becomes green. The cells have two vacuoles separated by a central cytoplasmic bridge. It contains the core. Pinnularia stores volutin, visible under a light microscope as dimly shining spherical bodies, and drops of oil. Under the shell, the cell is dressed in a mucilaginous pectin membrane. Pinnularia, which has a suture-nodular apparatus, actively moves, crawling along the substrate.

Pinnularia reproduces by division, running parallel to the valves. Each child valve receives one parent valve, while the second, completed valve, is always a hypotheca. As a result of this feature, at each division, one daughter cell is always somewhat smaller than the mother cell, and individuals of different sizes can be found in the population. The sexual process in Pinnularia was not found, auxospores are not formed. It can be assumed that large cells divide more often than small ones, and the smallest ones do not divide at all. The life cycle is monodiplobiont.

Object: r. pinnularia.

Progress

1. Consider pinnularia at b. led away. Sketch the cage from the side of the sash. Designate the cell membrane, suture, nodules, septa, chromatophore.

2. Sketch the cage from the side of the girdle. Label the epithecus and hypotheca.

Questions and tasks

1. What levels and types of morphological organization are typical for representatives of diatoms?

2. What are the structural features of diatom cells?

3. What is the structure of the shell of diatoms?

4. What are the principles of classification of diatoms?

5. What methods of reproduction are typical for diatoms?

6. How are sexual processes carried out in diatoms? What is an auxospore?

7. Where do diatoms live? What features of adaptation to the planktonic and benthic way of life do diatoms have? Give examples of planktonic and benthic diatoms.

8. Sketch schematically the life cycle of pinnularia and melosira. Sign on the diagram which generation is a sporophyte and which is a gametophyte, a set of chromosomes (haploid or diploid) for each generation and cells used for reproduction, the type of reduction division and the sexual process. Indicate the type of life cycle typical for these algae.

Department Brown algae (Phaeophyta)

The main pigments in brown algae are chlorophylls. a and With, carotenoids and xanthophylls, including fucoxanthin, which masks green pigments and gives algae a characteristic brown color. Spare products - laminarin (substance of carbohydrate nature); mannitol is a sugar alcohol and a small amount of fat. The pheoplasts are lamellar or more often numerous discoid (granular chromatophore) located in the perinuclear space under the outer nuclear membrane, which covers each pheoplast, forms a pheoplast endoplasmic reticulum. Pyrenoids protrude above the surface in the form of a kidney. The cells have one nucleus, large vacuoles with cell sap and small vacuoles containing tannins and called physodes.

The shell consists of two layers: the outer mucilaginous, containing alginic acid, and the inner, formed by a special kind of cellulose - alguose. Monadic cells with two heterocont and heteromorphic flagella are located on the lateral side of the cell. The anterior is long pinnate, covered with mastigonemes, the posterior is short and smooth. The range of morphological structures is large: from filamentous heterotrichous to differentiated lamellar tissue forms. In all brown algae, with the exception of representatives of the Fucus order, which lack asexual reproduction and are diplobionts, a change in generations is observed: in some it is isomorphic, in others it is heteromorphic. These different types life cycle are the basis for the modern division of the department of brown algae into three classes.

With few exceptions, brown algae are marine algae, especially abundant in the cold waters of the northern and southern hemispheres.

Class Isogenerate (Isogeneratophyceae)

The class Isogenate includes algae with isomorphic alternation of generations or with heteromorphic, but with the dominance of the gametophyte.

Order Ectocarp (Ectocarpales) includes heterotrichous forms.

Genus Ectocarpus (Ectocarpus)

Ectocarpus is a widespread marine, benthic algae, found in all latitudes in coastal strip seas and oceans. Algae settles on rocks and other underwater objects, including plants. Being tolerant to different water salinity, ectocarpus participate in fouling of ships. The temperature range of ectocarpus habitats is also wide. It grows both in cold and warm seas, and is active in both summer and winter. Ectocarpus is a macroscopic (up to 60 cm) algae, filamentous heterotrichous, having the appearance of branched bushes.

At the base are horizontal creeping rhizoids that attach the algae to the substrate. The vertical branches at the base of the thallus, covered with a bark of rhizoidal filaments, become thinner towards the apex and end in long colorless cells. The increase is due to the division of cells located in different parts of the thallus. In the cells of the ectocarpus, there are small vacuoles with cell sap, one nucleus in the parietal layer of the cytoplasm, and several ribbon-like chromatophores with pyrenoids. In senescent cells, the chromatophore becomes disc-shaped.

Ectocarpus reproduction is asexual and sexual. Meiozoospores, kidney-shaped with two unequal flagella attached to the lateral surface, are formed in unicellular sporangia sitting on a unicellular stalk. Such sporangia are formed on diploid sporophyte plants. On haploid plants, multi-nested reproductive organs are laid. Each nest produces one reproductive cell of the monad organization. Most often, these cells behave like gametes and merge to form a zygote. They are morphologically the same type, but their behavior differs: physiologically, female gametes are less mobile and quickly settle to the bottom; physiologically male are more active. The zygote develops into a diploid sporophyte. The cycle described above corresponds to the diplo-haplobiont type with isomorphic alternation of generations, but the ectocarpus has deviations from this cycle, for example, gametes can germinate parthenogenetically without fertilization, giving new haploid individuals. Thus, apparently, the possible complete adaptation of the ectocarpus to the conditions of existence is achieved and its wide ecological amplitude is explained.

Objects: r. ectocarpus (herbarium specimens, micropreparations).

Progress

1. Consider the herbarium specimens of the ectocarpus. Sketch the appearance of the heterotrichous thallus of the ectocarpus.

2. Consider at b. led away. and draw from the preparation areas of the ectocarpus thallus with multi-chambered gametangia and single-chambered sporangia. Name the cells of the thallus, gametangia, sporangia.

Class Heterogenerate (Heterogeneratophyceae)

The heterogeneous class is characterized by a heteromorphic alternation of generations with sporophyte dominance and microscopic small gametophytes.

Includes algae with a complex thallus having a tissue structure. The growth is carried out due to the division of cells located at the point of transition of the leaf-shaped part of the thallus to the petiole (intercalary growth).

Genus Laminaria (Laminaria)

Two types of kelp are known and widespread in the northern seas: L. sugar (L.saccharina (L.) Lamour) and L. palmate (L.digitata (Hudz.Lam)), which form entire plantations in the upper sublittoral and are commercial algae . Laminaria is called "seaweed" and is a valuable food product used in animal feeding, as well as the manufacture of various food products and medicines for humans.

Laminaria is a large, complexly differentiated benthic attached algae, with a true tissue structure. Its meristematic cells are able to divide in three mutually perpendicular directions and form three-dimensional structures in which all cells are connected to each other by plasmodesmata. The thallus of the kelp is differentiated into three clearly distinguishable parts: powerful claw-like rhizoids, with which it attaches to the substrate, a radially symmetrical part, the so-called petiole, and a flattened plate. The first two structures are perennial, while the lamina dies and grows again due to the intercalary meristem located in the upper part of the petiole. The internal organization of the kelp body is also quite complex. The petiole from the surface has densely closed cells containing grains of pheoplasts. In the deeper layers, the cells are colorless and elongated in the longitudinal direction. In the center of the cell are located loosely and form the core. The petiole gradually grows in thickness, and layers resembling growth rings are clearly visible on the transverse section. In the anatomical structure of the plate, the small cell cortex is also distinguished. In the center there is a "vein", the cells of which resemble in their structure the sieve cells of higher plants.

Laminaria reproduce sexually and asexually. Sporangia are located on the surface of the plate, forming whole spore-bearing areas or fields, on which sac-like sporangia and elongated sterile paraphyseal processes are located in a palisade layer. In sporangia, after reduction division, biflagellate reniform meiozoospores are formed, germinating into haploid organisms. The female and male gametophytes differ from the sporophyte. These are microscopic filamentous, underdeveloped plants (growths). They are short-lived, their main function is the production of gametes. The sexual process is oogamy. The zygote germinates without a dormant period and develops into a diploid sporophyte. Thus, almost all active life of kelp occurs in the diploid state. The development cycle is diplohaplobiont with heterotrophic alternation of generations, with sporophyte dominance.

End of introductory segment.

ALGAE: CLASSIFICATION OF ALGAE

To the article ALGAE

In the past, algae were considered primitive plants (without specialized conductive or vascular tissues); they were isolated in the subdivision of algae (Algae), which, together with the subdivision of fungi (Fungi), constituted the division of thallus (layer), or lower plants (Thallophyta), one of the four divisions of the plant kingdom (some authors use the zoological term instead of the term "department" type of"). Further, the algae were divided by color - into green, red, brown, etc. Color is strong enough, but not the only basis for general classification these organisms. The types of formation of their colonies, methods of reproduction, features of chloroplasts, cell wall, reserve substances, etc. are more essential for the selection of various groups of algae. The old systems usually recognized about ten such groups, which were considered classes. One of the modern systems refers to "algae" (this term has lost its classification value) eight types (divisions) of the protist kingdom (Protista); however, this approach is not recognized by all scientists.

Green algae make up the division (phylum) Chlorophyta of the protist kingdom. They are usually the color of grass green (although the color may vary from pale yellow to almost black), and their photosynthetic pigments are the same as those of ordinary plants. Most are microscopic freshwater forms. Many species grow on the soil, forming felt-like raids on its moist surface. They are unicellular and multicellular, form filaments, spherical colonies, leaf-shaped structures, etc. Cells are motile (with two flagella) or immobile. sexual reproduction - different levels difficulty depending on the type. Several thousand species have been described. The cells contain a nucleus and several distinct chloroplasts. One of the well-known genera is Pleurococcus, a single-celled algae that forms the green patches often seen on tree bark. The genus Spirogyra is widespread - filamentous algae that form long fibers of mud in streams and cold rivers. In spring, they float in sticky, yellowish-green clumps on the surface of ponds. Cladophora grows in the form of soft, strongly branched "bushes" that attach themselves to stones along the banks of rivers. Basiocladia forms a green coating on the back of freshwater turtles. The water mesh (Hydrodictyon) consisting of many cells, living in stagnant waters, really resembles a "string bag" in structure. Desmidia - unicellular green algae that prefer soft swamp water; their cells are distinguished by a bizarre shape and a beautifully ornamented surface. In some species, the cells are connected in filamentous colonies. In the free-floating colonial algae Scenedesmus, sickle-shaped or oblong cells are arranged in short chains. This genus is common in aquariums, where its mass reproduction leads to the appearance of a green "fog" in the water. The largest green algae is sea lettuce (Ulva), a leaf-shaped macrophyte.

Red algae (crimson) make up the department (type) Rhodophyta of the protist kingdom. Most of them are marine leafy, bushy or crusty macrophytes living below the low tide line. Their color is predominantly red due to the presence of the pigment phycoerythrin, but may be purple or bluish. Some purples are found in fresh water, mainly in streams and clear fast rivers. Batrachospermum is a gelatinous, highly branched algae composed of brownish or reddish, bead-like cells. Lemanea is a brush-like form often growing in fast-flowing streams and waterfalls where its thalli attach to rocks. Audouinella is a filamentous alga found in small rivers. Irish moss (Chondrus cripus) is a common marine macrophyte. Purples do not form mobile cells. Their sexual process is very complex, and one life cycle includes several phases.

Brown algae make up the Phaeophyta division (type) of the protist kingdom. Almost all of them are inhabitants of the sea. Only a few species are microscopic, and among the macrophytes are the largest algae in the world. The latter group includes kelp, macrocystis, fucus, sargassum and lessonia ("sea palms"), the most abundant along the coasts of cold seas. All brown algae are multicellular. Their color varies from greenish yellow to dark brown and is due to the pigment fucoxanthin. Sexual reproduction is associated with the formation of motile gametes with two lateral flagella. Instances that form gametes are often completely different from organisms of the same species that reproduce only by spores.

Diatoms (diatoms) are combined into the class Bacillariophyceae, which, in the classification used here, is included, together with golden and yellow-green algae, in the department (type) Chrysophyta of the kingdom of protists. Diatoms are a very large group of unicellular marine and freshwater species. Their color is yellow to brown due to the presence of the pigment fucoxanthin. The protoplast of diatoms is protected by a box-shaped silica (glass) shell - a shell consisting of two valves. The hard surface of the valves is often covered with a complex pattern of striae, tubercles, pits, and ridges characteristic of the species. These shells are one of the most beautiful microscopic objects, and the clarity of distinguishing their patterns is sometimes used to test the resolving power of a microscope. Usually the valves are pierced with pores or have a gap called a seam. The cell contains the nucleus. In addition to cell division in two, sexual reproduction is also known. Many diatoms are free-swimming forms, but some are attached to underwater objects with slimy stalks. Sometimes cells are combined into threads, chains or colonies. There are two types of diatoms: cirrus with elongated bilaterally symmetrical cells (they are most abundant in fresh waters) and centric, whose cells, when viewed from the valve, look rounded or polygonal (they are most abundant in the seas).

As already mentioned, the shells of these algae persist after cell death and settle to the bottom of water bodies. Over time, their powerful accumulations are compacted into a porous rock- diatomite.

Flagella. These organisms, due to their ability to “animal” nutrition and a number of other important features, are now often referred to as the subkingdom of protozoa (Protozoa) of the protist kingdom, but they can also be considered as a division (type) of Euglenophyta of the same kingdom that is not included in the Protozoa. All flagella are unicellular and motile. Cells are green, red or colorless. Some species are capable of photosynthesis, while others (saprophytes) absorb dissolved organic matter or even swallow its solid particles. Sexual reproduction is known only in some species. A common pond dweller is Euglena, a green algae with a red eye. She swims with the help of a single flagellum, is capable of both photosynthesis and nutrition of ready-made organic matter. Euglena sanguinea can turn pond water red in late summer.

Dinoflagellates. These single-celled flagellar organisms are also often referred to as protozoa, but they can also be distinguished as an independent department (type) Pyrrophyta of the protist kingdom. They are mostly yellow-brown, but they can also be colorless. Their cells are usually mobile; the cell wall is absent in some species, and sometimes it is of a very bizarre shape. Sexual reproduction is known only in a few species. The marine genus Gonyaulax is one of the causes of the "red tides": near the coasts, it is so abundant that the water takes on an unusual color. This algae releases toxic substances, sometimes leading to the death of fish and shellfish. Some dinoflagellates cause water phosphorescence in tropical seas.

Golden algae are included, along with others, in the Chrysophyta division (type) of the protist kingdom. Their color is yellow-brown, and the cells are mobile (flagellated) or motionless. Reproduction is asexual with the formation of silica-impregnated cysts.

Yellow-green algae are now usually combined with golden algae into the division (type) Chrysophyta, but they can also be considered an independent division (type) Xanthophyta of the protist kingdom. In form, they are similar to green algae, but differ in the predominance of specific yellow pigments. Their cell walls sometimes consist of two halves entering one another, and in filamentous species these valves are H-shaped in longitudinal section. Sexual reproduction is known only in a few forms.

Charovye (rays) are multicellular algae that make up the Charophyta division (type) of the protist kingdom. Their color varies from grayish green to gray. Cell walls are often encrusted with calcium carbonate, so the dead remains of chars are involved in the formation of marl deposits. These algae have a cylindrical, stem-like main axis, from which lateral processes extend in whorls, similar to plant leaves. Characeae grow vertically in shallow water, reaching a height of 2.5-10 cm. Sexual reproduction. Characeae are unlikely to be close to any of the groups listed above, although some botanists believe that they are descended from green algae. See also PLANT SYSTEMATICS.

Collier. Collier's Dictionary. 2012

See also interpretations, synonyms, meanings of the word and what ALGAE is: CLASSIFICATION OF ALGAE in Russian in dictionaries, encyclopedias and reference books:

• SEAWEED in the Encyclopedia of Biology:
  , an extensive group of photosynthetic organisms, sometimes allocated to a separate kingdom of plants. Includes 12 divisions (blue-green algae, brown algae, green algae, ...
• SEAWEED
  (Algae) - lower plant organisms, ranked as a sub-kingdom of spore, or cryptogamous, plants (Sporophyta s. Kryptogamae). Together with mushrooms and lichen ...
• SEAWEED
  (algae)? lower plant organisms classified as a sub-kingdom of spore-bearing, or cryptogamous, plants (Sporophyta s. Kryptogamae). Together with mushrooms and lichen ...
• SEAWEED in Collier's Dictionary:
  (Algae), a vast and heterogeneous group of primitive, plant-like organisms. With few exceptions, they contain the green pigment chlorophyll, which is essential for...
• CLASSIFICATION in the Newest Philosophical Dictionary:
  (lat. classis - category, class and facio - I do, lay out) - a multi-stage division of the logical volume of a concept (logic) or any ...
• CLASSIFICATION
  GOODS - assignment by customs authorities Russian Federation specific goods to the items specified in the Commodity Nomenclature for Foreign Economic Activity (TN VED). …
• CLASSIFICATION in the Dictionary of Economic Terms:
  FIXED ASSETS - a grouping of fixed assets established by the USSR State Statistics Committee and including 12 types: buildings; structures; transmission devices; cars and equipment; transport …
• CLASSIFICATION in the Dictionary of Economic Terms:
  BUDGET - see BUDGET CLASSIFICATION ...
• CLASSIFICATION in the Dictionary of Economic Terms:
  - distribution, spacing of objects, concepts, names into classes, groups, categories, in which objects with c.-l. fall into one group. general ...
• CLASSIFICATION in the Encyclopedia of Biology:
  in biology, the distribution of the diversity of living organisms in a certain order according to a system. Classification is based on a set of features that enable ...
• SEAWEED in the Bible Encyclopedia of Nicephorus:
  or SEA GRASS (Jon 2:6) sea, water grass, as read in the Russian translation in the indicated quote. Was embraced by sea grass ...
• SEAWEED in Medical terms:
  (algae) a group of autotrophic chlorophyll-bearing, usually aquatic lower plants, not divided into roots, stems and leaves, capable of absorbing carbon dioxide in ...
• CLASSIFICATION
  (from lat. classis - category class and ... fication), in logic - a system of subordinate concepts (classes of objects) of any field of knowledge or ...
• SEAWEED in the Big Encyclopedic Dictionary:
  a group of lower aquatic plants that usually contain chlorophyll and produce organic matter through photosynthesis. The body of the algae is a thallus that does not have ...
• SEAWEED in big Soviet encyclopedia, TSB:
  (Algae), a group of lower, autotrophic, usually aquatic plants; contain chlorophyll and other pigments and produce organic matter through photosynthesis. …
• CLASSIFICATION in the Encyclopedic Dictionary of Brockhaus and Euphron:
  a very important logical device that is used in the study of the subject and which is based on the logical division of concepts. Indeed, the classification is not ...
• CLASSIFICATION in the Modern Encyclopedic Dictionary:
  
• CLASSIFICATION
  (from the Latin classis - category, class and ... fication) (in logic), a system of subordinate concepts (classes of objects) of any field of knowledge or activity ...
• CLASSIFICATION in the Encyclopedic Dictionary:
  and, well. 1. pl. no. The distribution of certain objects into classes depending on their properties.||Cf. RUBRICATION. 2. …
• CLASSIFICATION in the Encyclopedic Dictionary:
  , -i, f. 1. see classify. 2. System, according to a swarm of something. .classified. K. Sciences. Library k. II adj. classification, th, ...
• CLASSIFICATION
  CLASSIFICATION OF LANGUAGES, the study and grouping of the world's languages ​​in various ways. features: genetic K.I. (genealogical) - on the basis of kinship, i.e. common origin...
• CLASSIFICATION in the Big Russian Encyclopedic Dictionary:
  CLASSIFICATION OF SCIENCES, disclosure of the interconnection of sciences on the basis of a definition. principles (objective, subjective, coordination, subordination, etc.) and the expression of their connection ...
• CLASSIFICATION in the Big Russian Encyclopedic Dictionary:
  CLASSIFICATION (hearth), separation of particles of crushed minerals into homogeneous products (classes) in terms of size, density, and other products. K. is produced in ...
• CLASSIFICATION in the Big Russian Encyclopedic Dictionary:
  CLASSIFICATION (from lat. classis - category, class and ... fication) (in logic), a system of subordinate concepts (classes of objects) c.-l. areas…
• SEAWEED in the Big Russian Encyclopedic Dictionary:
  ALGAE, preim group. water. organisms, usually containing chlorophyll and producing organic. in-va in the process of photosynthesis. The body of V. is a thallus that does not have ...
• CLASSIFICATION in the Encyclopedia of Brockhaus and Efron:
  ? a very important logical device that is used in the study of the subject and which is based on the logical division of concepts. Indeed, the classification is ...
• CLASSIFICATION
  classification, classification, classification, classification, classification, classification, classification, classification, classification, classification, classification, classification, classification, classification, ...
• SEAWEED in the Full accentuated paradigm according to Zaliznyak:
  grow up, grow up, grow up, grow up, grow up, grow up, ...
• CLASSIFICATION in the Dictionary of Linguistic Terms:
  (from lat. classis - rank + facere - to put) vowels, see vowel sounds ...
• CLASSIFICATION in the Popular Explanatory-Encyclopedic Dictionary of the Russian Language:
  -and, well. 1) The system of subordinate concepts (classes of objects) in some branch of knowledge, compiled on the basis of taking into account the properties of objects and regular ...
• CLASSIFICATION in the Thesaurus of Russian business vocabulary:
  
• CLASSIFICATION in the New Dictionary of Foreign Words:
  (lat.; see classify) 1) a system of subordinate concepts (classes of objects, phenomena) in some. branch of knowledge, compiled on the basis of ...
• CLASSIFICATION in the Dictionary of Foreign Expressions:
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1. ALGAE ( ALGAE)

1.1 GENERAL CHARACTERISTICS

Algae are a group of predominantly aquatic organisms. A characteristic feature of all algae is that their body is not divided into vegetative organs (root, stem, leaf), but is represented by a thallus, or thallus. For this reason, they are called thallus, or thallus organisms. Unlike higher plants, they usually lack tissues, and the organs of sexual reproduction are usually unicellular. Common to algae is their ability to autotrophic mode of nutrition due to the presence of a photosynthetic apparatus. At the same time, in some algae, along with autotrophic nutrition, heterotrophic nutrition also exists.

More than 40,000 species of algae are known, which are combined into 11 divisions: diatoms - about 20,000 species, green - 13-20,000, red - about 4,000, blue-green - about 2,000, brown - about 1,000, dinophytes and cryptophytes - more than 1,000, yellow-green, golden, characeae - more than 300 in each division, euglenoids - about 840 species. According to the well-known Belarusian algologist T.M. Mikheeva (1999) found 1832 species of algae in Belarus, and together with intraspecific taxa - 2338 representatives. The discovered species belong to 363 genera in 134 families from 10 divisions. At the same time, 21 species of algae are listed in the Red Book of the Republic of Belarus.

Algae structure. Algae within the thallus type of structure are distinguished by exceptional morphological diversity. Their body can be unicellular, colonial, multicellular. Their sizes within each of these forms differ in a huge range - from microscopic (1 micron) to gigantic (there are species reaching several tens of meters). Taking into account the great morphological diversity of the vegetative body, algae can be divided into several categories according to their structure, forming the main stages of morphological evolution.

The monadic (flagellar) structure is characteristic of unicellular and colonial organisms and is characterized by the presence of cells of one, two or more flagella in them, which determine active movement in the water. This structure prevails in dinophytes and cryptophytes, golden and euglena algae. In more highly organized algae, cells that serve for asexual (zoospores) or sexual (gametes) reproduction have a monadic structure.

The amoeboid (rhizopodial) structure is characterized by the absence of a permanent cell shape, a dense membrane and flagella. These algae, like amoeba, move with the help of pseudopodia, which are preserved in dinophytes, golden and yellow-green algae.

The palmelloid (hemimonasal or capsal) structure is a combination of many immobile cells immersed in a common mucus, but without plasma connections. The palmelloid structure is widely represented in green, yellow-green and golden algae; in other departments, it is less common or absent altogether.

The coccoid structure is characterized by immobile cells various shapes and sizes, with a dense cell wall, single or connected in a colony (cenobia). Such a structure is found in almost all departments (with the exception of euglena) algae, and in diatoms it is the only one; in other representatives it is observed in development cycles (aplanospores, akinetes, tetraspores, etc.).

The filamentous (trichal) structure in the world of algae is the simplest form multicellular thallus and is a connection of immobile cells in threads, between which physiological interaction is carried out with the help of plasmodesmata. Threads can be simple and branching, free-living, attached and united most often in mucous colonies. The filamentous structure is presented among green, golden, yellow-green, red algae.

The multifilamentous (heterotrichal) structure is a more complex variant of the filamentous structure, which is characterized by two systems of filaments: those that creep along the substrate and those that extend vertically from them.

The heterotrichous structure is characteristic of many blue-green, green, char, golden, yellow-green, red and brown algae and can be a permanent or temporary form.

Pseudoparenchymal (false tissue) structure is characterized by the formation of large voluminous thalli as a result of the fusion of threads of a multi-filamentous thallus, sometimes accompanied by differentiation of "tissues". Since the latter, in terms of the method of formation, differ from the real ones, they are called false tissues. Found in some red algae.

The siphonal (siphon) structure is a thallus, often of large size and complex morphological differentiation, without cell partitions and usually with many nuclei. The siphonal type of organization is present in some green and yellow-green algae.

The siphonocladal structure is found in some filamentous green algae, which are characterized by segregational division of multinucleated cells: the protoplast breaks up into rounded parts surrounded by a membrane, giving rise to new segments of the thallus.

Cell structure. The organization of the cell of most algae (except blue-green ones) differs little from the organization of typical cells of higher plants, but it also has its own characteristics. The cell of most algae is dressed in a permanent cell membrane, has a two-phase system, consists of an amorphous matrix, hemicellulose or pectin substances, in which fibrous skeletal elements - microfibrils are immersed. In many algae, additional components are deposited: calcium carbonate (characeae, acetobularia, padina), alginic acid (brown), iron (red). In the life of a plant cell, an important role is played by the presence in the shell of first pectin and then cellulose fractions, which provide support and protective functions, as well as the ability to permeate and grow. The cell membrane can be whole or consists of two or more parts, penetrated by pores, and can carry various outgrowths. Under the shell is the protoplast, including the cytoplasm and nucleus.

Algae is the only group where there are all three types of cellular organization: prokaryotic (blue-green algae, where there are no nuclei, their role is played by the nucleoid); mesokaryotic (dinophytes, there is a nucleus, but primitive) and eukaryotic (algae of other divisions are real nuclear organisms).

The cytoplasm in most algae is located in a thin wall layer, surrounding a large central vacuole with cell sap. The vacuole is absent in the cells of blue-green algae and monads (pulsating vacuoles are noted in freshwater monads). In the cytoplasm of eukaryotic algae, elements of the endoplasmic reticulum, ribosomes, mitochondria, the Golgi apparatus, chromatophores, and cell nuclei are clearly distinguishable; there are also lysosomes, peroxisomes, spherosomes.

In algal cells (with the exception of blue-green ones), chromatophores (chloroplasts) are especially noticeable from organelles, which, unlike chloroplasts of higher plants, are diverse in shape, color, number, structure, and location in the cell. They can be cup-shaped (chlamydomonas), spiral (spirogyra), lamellar (pennate diatoms), cylindrical (edogonium). In many algae, chromatophores are numerous and look like grains or discs located in the parietal cytoplasm (green with a siphon organization, brown, red). Chromatophores are sheathed, composed of stroma, lamellar structures that resemble flattened sacs and are called thylakoids. They contain pigments. In addition, the chromatophore matrix contains ribosomes, DNA, RNA, lipid granules, and special inclusions of pyrenoids. The pyrenoid is a specific formation inherent in all algae (with the exception of blue-green ones) and a small group of mosses.

Algae reproduction. Asexual reproduction in unicellular algae is carried out by cell division, in colonial and filamentous algae - as a result of the breakdown of colonies or filaments into separate fragments; in a few algae, special reproductive organs are formed, for example, nodules in characeae, akinetes (special cells with a large amount of reserve substances and pigments) in greens, etc. Such reproduction is often called vegetative.

Asexual reproduction also occurs through immobile spores (aplanospores) or zoospores (flagellated spores), which are formed by protoplast division of ordinary or special cells called sporangia. In a number of representatives of green algae, aplanospores sometimes acquire all the distinctive features of this cell already in the mother cell. In such cases, they talk about autospores. Reproduction by means of spores is called proper asexual reproduction.

Sexual reproduction is characterized by the presence of a sexual process, one of the most important stages of which is fertilization, i.e. fusion of haploid sex cells - gametes. As a result of fertilization, a zygote is formed with a new combination of hereditary traits, which becomes the ancestor of a new organism.

In algae, the following forms of the sexual process are distinguished: chologamy - the fusion of two single-celled individuals; isogamy - the fusion of mobile gametes that are identical in structure and size; heterogamy - the fusion of mobile gametes of different sizes (the larger one is considered female); oogamy - the fusion of a large immobile egg with a small mobile male gamete - a spermatozoon or an immobile spermatozoon without a shell (in red algae); conjugation - the fusion of protoplasts of unspecialized cells. Gametes are formed in cells that do not differ from vegetative cells, or in special cells called gametangia. Gametangia containing an egg (rarely several) are called oogonia, and those in which spermatozoa or spermatozoa are formed are called antheridia. In primitive algae, each individual is able to form both spores and gametes, depending on the season and external conditions; in others, the functions of asexual and sexual reproduction are performed by different individuals - sporophytes (form spores) and gametophytes (form gametes). The main types of life cycles of algae.

1. The haplophase type is characterized by the absence of alternation of generations. The entire vegetative life of algae takes place in a haploid state, that is, they are haplonts. Only the zygote is diploid, the germination of which is accompanied by a reduction division of the nucleus (zygotic reduction). The plants that develop in this case are haploid. Examples are many green (volvox, most chlorococcal, conjugates) and char algae.

2. The diplophase type is distinguished by the fact that the entire vegetative life of algae is carried out in a diploid state, and the haploid phase is represented only by gametes. Before their formation, a reduction division of the nucleus occurs (gametic reduction). The zygote without nuclear division grows into a diploid thallus. These algae are diplonts. This type of development is characteristic of many green algae with a siphon structure, all diatoms and some representatives of brown algae (Fucal order).

3. The diplohaplophase type is characterized by the fact that in the cells of diploid thalli (sporophytes) of many algae, the reduction division of the nucleus precedes the formation of zoo- or aplanospores (sporic reduction). Spores develop into haploid plants (gametophytes) that reproduce only sexually. A fertilized egg - a zygote - germinates into a diploid plant that carries organs of asexual reproduction. Thus, in these algae there is an alternation of developmental forms (generations): a diploid asexual sporophyte and a haploid sexual gametophyte. Both generations may not differ in appearance and occupy the same place in the development cycle (isomorphic change of generations) or sharply differ in morphological features (heteromorphic change of generations). An isomorphic change in generations is characteristic of a number of green (ulva, enteromorph, cladophora), brown and most red algae. A heteromorphic change of generations occurs with a predominance of both gametophyte and sporophyte (characteristic mainly of brown, less often green and red algae).

Water is the main living medium for algae. In addition, such factors as light, temperature, water salinity, chemical composition of the substrate, etc., play an extremely important role in their life. Depending on the environmental conditions, algae form various groups or communities (cenoses), each of which is characterized by a more or less certain species composition.

1.2 METHODS FOR COLLECTING, STORING AND STUDYING ALGAE

Algae can be collected from early spring to late autumn, and ground - in places not covered with snow, throughout the year. To collect them, you need to take jars with a wide mouth and well-fitting corks, a bag for them, a knife, a sharp scraper, plankton net, a vial of formalin, boxes or plastic bags for collecting terrestrial algae, writing paper for labels, a notepad, a pencil.

Methods for collecting and studying algae are determined primarily by the ecological and morphological features of representatives of various departments and ecological groups. Let us consider the main methods of collecting and studying algae from various water bodies for the purposes of floristic-systematic and partially hydrobiological studies.

Collection of phytoplankton. The choice of phytoplankton sampling method depends on the type of reservoir, the degree of development of algae, research objectives, available instruments, equipment, etc. preliminary concentration of microorganisms living in the water column. One such method is filtering water through plankton nets (description of plankton nets and other devices and devices for collecting algae).

When collecting plankton from the surface layers of a reservoir, the plankton net is lowered into the water so that the upper opening of the net is at a distance of 5-10 cm above the water surface. A vessel of a certain volume draws water from the surface layer (up to 15-20 cm deep) and pours it into the net, thus filtering 50-100 liters of water. In large reservoirs, plankton samples are taken from a boat: a plankton net is pulled on a thin rope behind a moving boat for 5-10 minutes. For vertical collections of plankton, nets of a special design are used. In small bodies of water, plankton samples can be collected from the shore by carefully scooping water in a vessel in front of you and filtering it through a net, or by throwing a net on a thin rope into the water and carefully pulling it out. For the quantitative accounting of phytoplankton, the volume of samples is made by special devices - bathometers - of various designs. The bathometer of the Rutner system has received wide application in practice. Its main part is a cylinder made of metal or plexiglass, with a capacity of 1 to 5 liters. The device is equipped with top and bottom covers tightly closing the cylinder. Under the water, the bathometer is lowered with the lids open. When the required depth is reached, as a result of strong shaking of the rope, the covers close the holes of the cylinder, which, when closed, is removed to the surface. The water enclosed in the cylinder is poured into the prepared vessel through a side branch pipe equipped with a tap. When studying phytoplankton of the surface layers of water, samples are taken without the help of a bathometer by scooping water into a vessel of a certain volume.

Collection of phytobenthos. To study the species composition of phytobenthos on the surface of a reservoir, it is sufficient to extract a certain amount of bottom soil and sediments on it. In shallow waters (up to 0.5-1.0 m deep), this is achieved using a test tube lowered to the bottom or a siphon - a rubber hose with glass tubes at the ends, into which silt is sucked. At depths, quality samples are taken using a bucket or a glass attached to a stick, as well as various rakes, "cats", dredges, bottom grabs, silos, etc.

Collection of periphyton. In order to study the species composition of periphyton, plaque on the surface of various underwater objects (pebbles, gravel, stones, stems and leaves of higher plants, mollusk shells, wooden and concrete parts of hydraulic structures, etc.) is removed using an ordinary knife or special scrapers. However, many interesting organisms die in the process; some of them are carried away by water currents, the organs of attachment of algae to the substrate are destroyed, the picture of the mutual placement of the components of the biocenosis is disturbed. Therefore, it is better to collect algae together with the substrate, which is completely or partially carefully removed to the surface of the water so that the current does not wash away the algae from it. The extracted substrate (or its fragment), together with algae, is placed in a vessel prepared for the sample and filled with only a small amount of water from the same reservoir for the purpose of further study. collected material live or 4% formaldehyde solution. Ground or air algae are collected, if possible, together with the substrate in sterile paper bags or in glass vessels with a 4% formaldehyde solution.

Labeling and fixation of samples. Keeping a field diary. To study algae in a living and fixed state, the collected material is divided into two parts. Living material is placed in sterile glass vessels (test tubes, flasks, jars), closed with cotton plugs, and not filled to the top, or in sterile paper bags. In order to better keep the algae alive in expeditionary conditions, water samples are packed in wet wrapping paper and placed in boxes. Samples should be periodically unpacked and exposed to diffused light to support photosynthetic processes and enrich the environment with oxygen.

Collected samples are carefully labeled. The labels, filled in with a simple pencil or paste, indicate the sample number, the time and place of collection, the collection tool and the name of the collector. The same data are recorded in the field diary, in which, in addition, the results of measurements of pH, water and air temperature, a schematic drawing, a detailed description of the studied reservoir, the higher aquatic vegetation developing in it, and other observations are entered.

Qualitative study of the collected material. The material is preliminarily examined under a microscope in a living state on the day of collection in order to note the qualitative state of the algae before the onset of changes caused by storage of live material or fixation of samples (formation of reproductive cells, colonies, loss of flagella and motility, etc.). In the future, it is studied in parallel in a living and fixed state. Preparations are prepared for microscopic examination of algae: a drop of the liquid under study is applied to a glass slide and covered with a coverslip. If algae live out of water, they are placed in a drop of tap water or hydrated glycerin. If long-term observations of the same object are required, the hanging drop method gives a good result. A small drop of the test liquid is applied to a clean cover slip, after which the cover slip, the edges of which are coated with paraffin, paraffin oil or petroleum jelly, is placed drop down on a special glass slide with a hole in the middle so that the drop does not touch the bottom of the hole. Such a preparation can be studied for several months, keeping it between work in a humid chamber. When identifying algae, it is necessary to achieve the accuracy of their determination. When studying the original material, it is necessary to note any, even minor deviations in size, shape and other morphological features, fix them in descriptions, drawings and microphotographs.

Method of quantitative accounting of algae. Samples of phytoplankton, phytobenthos and periphyton can be subjected to quantitative accounting. Data on the abundance of algae are the initial data for determining their biomass and recalculating other quantitative indicators per cell or biomass unit. The number of algae can be expressed in the number of cells, coenobia, segments of threads of a certain length, etc. The number of planktonic algae is counted using counting chambers (Fuchs-Rosenthal, Nageott, Goryaev, etc.) with a microscope magnification of 420 times. The average amount of algae obtained from at least three counts is recalculated for a given volume of water. Since the substrate for the settlement of algae can be underwater objects (stones, piles, plants, animals, etc.), in some cases the amount of algae is calculated per unit surface, in others - per unit mass.

1.3 POSITION OF ALGAE IN THE PRESENT SYSTEM OF THE ORGANIC WORLD

To create a natural system of the organic world, taxonomists use a set of the most significant features of organisms included in a particular taxonomic category. These signs include:

1) the historical development of a group of living organisms based on fossil remains;

2) features of the morphological and anatomical structure of modern species;

3) features of reproduction and embryonic development;

4) physiological and biochemical features;

5) karyotype, determined by the number, size and shape of chromosomes;

6) type of reserve nutrients

7) distribution on our planet and a number of others.

The generally accepted system of the organic world has not yet been created. Until now, the number of empires, kingdoms, sub-kingdoms, types (departments) distinguished by different authors is not the same. A fundamentally new moment in this system of the organic world in comparison with the previous one is the allocation of the kingdom of Protista. The name "kingdom of Protista" ( Protista) proposed in 1866 by E. Haeckel. During most of the 20th century, supporters of the separation of protists into a separate kingdom strengthened their positions, although they excluded bacteria and sponges from it, but supplemented it with the rest of the protozoa, as well as some fungi and algae. Currently part of the kingdom Protista many authors include all single-celled and colonial eukaryotic organisms, regardless of the type of nutrition and functioning. This means that they are considered as a special level of organization of living matter. Understanding protists precisely as pretissue (rather than unicellular) allows various authors of systems to include in their composition (depending on what the author understands by tissue) all or some groups of multicellular algae (green, red, brown), mushroom-like organisms, or "pseudo-fungi" - hypochytridia ( Hyphochytridiomycota), oomycetes ( Oomycota) and labyrinthine ( Labyrinthulomycota). As a result, the kingdom of Protista united an extremely heterogeneous group of organisms, some of which were previously included in the kingdom of Animals (Protozoa), the kingdom of Fungi (acrasia and plasmodial mixomycetes, most of the lower fungi - chytridiomycetes and oomycetes), as well as in the kingdom of Plants (euglena, dinophytes, cryptophytes). , diatoms, golden, yellow-green, green algae).

Thus, the modern taxonomy of algae is characterized by the presence of many systems that differ from each other to a greater or lesser extent not only at the level of small taxa (genera, families, orders, classes) but also at the highest taxonomic levels (departments, subkingdoms, kingdoms,) . For example, charophytes in the same volume are considered by different authors as a department, class, or even order. Moreover, in one system they are assigned to the kingdom Plants, in another - to the kingdom Protista or Chromista. At the same time, according to a number of essential features (the presence, like in green plants, of chlorophyll a, carotenoids, as well as phycobilins like in red algae, oxygenic type of photosynthesis, etc.) cyanobacteria are very similar to algae. In this regard, they are often called blue-green algae and are considered in the course of algology.

2. CHARACTERISTICS OF ALGAE

2.1 DIVISION YELLOW GREEN ( XANTHOPHYTA)

The yellow-green algae department includes organisms that are at different stages of morphological differentiation of the thallus - unicellular, colonial and multicellular. Among them, predominantly coccoid, palmelloid or filamentous structures are found, less often - amoeboid, monadic, siphonal and lamellar. Mobile forms of yellow-green algae (including zoospores) are characterized by the presence of two unequal-sized flagella (lateral - short, beetle-shaped and anterior - long with mastigonemes) and yellow-green color of chromatophores, due to the presence of chlorophylls a and c, carotenes in and e, xanthophylls (antheraxanthin, lutein, zeaxanthin, washriaxanthin, violaxanthin and neoxanthin). Depending on the predominance of certain pigments, there are species with a light or dark yellow color, less often green, and in some - blue. Spare products - volutin, fat, often chrysolaminarin. In primitive forms, the contents of the cell are surrounded by a thin periplast, while in more highly organized representatives there is a pectin or cellulose membrane (solid or bicuspid). The cell membrane is often impregnated with iron salts, silica, lime, and has various sculptural decorations.

There are several chromatophores in the protoplast of the cell, which can be disc-shaped, lamellar, ribbon- or cup-shaped or star-shaped. One nucleus or many. Some species have pyrenoids. Movable forms have a stigma. Yellow-green algae can reproduce by longitudinal cell division, disintegration of colonies or filaments into separate sections, as well as by zoo- or aplanospores. The sexual process (iso- or oogamy) is known to a few. To endure unfavorable conditions, some species form cysts with a weakly silicified bivalve membrane. The algae of this division are found mainly in clean freshwater reservoirs, less often in the seas and brackish waters and soil.

2.1.1 Class Xanthophytaceae ( Xanthophyceae)

This class includes unicellular and multicellular organisms, predominantly of a coccoid structure; less commonly, a monadic, rhizopodial, palmelloid, filamentous, multifilamentous, or siphon body structure is observed. Monadic forms and stages with two unequal flagella and stigma located on cutting edge chromatophore, under its shell. The chromatophores are surrounded by a canal of the endoplasmic reticulum that continues into the outer membrane of the nuclear envelope.

In accordance with the types of organization of the thallus, the class is divided into six orders: heterochloride ( Heterochloridales), rhizochloride ( Rhizochloridales), heterogleal ( Heterogloeales), mischococcal ( mischococcales), botridial ( Botrydiales) and tribonemal ( Tribonematales).

Order Botridial ( Botridiales). Representatives of the order are characterized by a siphonal structure of the thallus. Outwardly, they can have a complex shape, but according to the structure of the protoplast, they are one giant multinucleated cell. As a rule, the thallus is differentiated into colored ground and colorless underground parts. Typical representatives of the order are the genera Botridium and Vosheria.

Genus botridium ( Botrydium) combines terrestrial attached siphon algae having a spherical, pear- or club-shaped form. Their underground part is a dichotomously branched system of colorless rhizoids. The cell is covered with a pectin membrane, which, saturated with lime, coarsens with age. Lamellar or disk-shaped chromatophores and numerous oil drops are located in the wall layer of the cytoplasm. Small nuclei are visible only after staining.

Botridium reproduces by zoospores, sometimes by auto- or aplanospores. Under unfavorable conditions (prolonged drying), the contents of the ground part (ball) move into rhizoids and break up into separate parts covered with a thick shell, forming resting cysts - rhizocysts. With the onset of favorable conditions, rhizocysts germinate into new individuals directly or through the zoospore stage.

More than 10 species are known, including 1 species - B. granular ( B. granulatum) - in Belarus. They develop on clay-silt deposits on the banks of water bodies, at the bottom of drying ponds, in the ruts of country and forest roads, on moist, nutrient-rich soils with a high content of lime.

Vosheria clan ( Vaucheria) includes algae, the thallus of which is irregularly and rarely branching filaments of delicate light green color with colorless branching rhizoids. This is one giant multinucleated cell. Its central part is occupied by a large vacuole with cell sap. Numerous disc-shaped chromatophores without pyrenoids and oil droplets are located in the wall layer of the cytoplasm.

Asexual reproduction is carried out by multi-flagellated and multi-nuclear zoo- and aplanospores. At the same time, the content at the ends of the branches becomes denser and darker, is separated by a septum from the common thread and turns into a zoosporangium, where one large zoospore is formed with numerous paired flagella along the periphery.

The sexual process in Vosheria is oogamous. Antheridium and one or two or several oogonia are formed on a thread or on special short branches. When the egg matures, a drop of contents emerges from the spout of the oogonium, attracting spermatozoa. One of them (with two flagella of unequal length) is introduced into the oogonium through the hole formed and fertilizes the egg. After fertilization, an oospore develops in the oogonium with a thick shell containing a lot of oil and hematochrome. After a dormant period, the reduction division of the nucleus occurs in it and it grows into a new haploid thread.

62 species are known, distributed throughout the globe. In Belarus, 1 species is noted - Vaucheria De Candolle sp.

Tribonemal order ( Tribonematales). It combines forms characterized by a filamentous structure of the thallus. These are the most highly organized representatives of yellow-green algae. In appearance, they are similar to ulothrixes from the Greens department and many species from the Golden algae department. A typical representative of this order is the genus Triboneme.

Tribonema genus ( Tribonema) includes algae whose filaments are unbranched. At first, they are attached to some substrate with the help of a basal cell, then, due to its death, they float to the surface of the reservoir and are already found as free-floating, forming a yellow-green mud. A characteristic feature by which tribonema filaments are easily distinguished from other filamentous algae is the peculiar outline of their ends in the form of two horns. This is due to the fact that the cell membrane of the triboneme is strong, bicuspid and consists of two identical halves. The edge of one half is on the edge of the other in the middle of the cage. During cell division, a cylindrical section of a new membrane is formed from its middle part, in which a transverse septum is laid. Thus, the halves of neighboring cells are firmly connected to each other, and when the thread breaks into pieces or breaks up into individual cells, characteristic H-shaped fragments of the shell are formed. There are usually several chromatophores in each cell of the triboneme, disc-shaped, without pyrenoids. During reproduction, one or two multiflagellate zoospores or aplanospores are formed in the cells, at the exit of which the valves diverge and the algae thread disintegrates. To endure adverse conditions, akinetes with a thick cell wall or cysts are used. 22 species of tribonemes are known, 6 of them are in Belarus. Distributed mainly in the coastal zone of various reservoirs on aquatic plants, stones, some - in the soil; often form soft cotton-like, non-mucilaginous, yellow-green sods.

2.2 DIVISION BROWN ALGAE ( PHAEOPHYTA)

The department Brown algae includes numerous, mainly macroscopic, multicellular algae of simple and complex structure. Their sizes vary from a few millimeters to several meters (sometimes up to 60 m or more). The thallus grows as a result of intercalary growth or due to the activity of the apical cell. In appearance, these are branched bushes, crusts, plates, cords, ribbons, complexly dissected into stem- and leaf-shaped organs. The thalli of some large representatives have air bubbles that hold the branches in the water in an upright position. For attachment to the ground, rhizoids or disc-shaped growths at the base of the thallus are used - the basal disc.

According to the morphological and anatomical differentiation of the thallus, brown algae are at a higher level than all other groups. Among them, neither unicellular nor colonial forms, nor thalli in the form of a simple unbranched thread are known. The thallus of the simplest living brown algae is heterotrichous, while the vast majority have thalli of a false or true tissue structure (assimilatory, storage, mechanical, conductive tissues are distinguished).

The shell of the cells is mucilaginous on the outside, consists of pectin substances and an inner cellulose layer. Mucus protects cells from mechanical influences, drying out during low tide, etc. In the cytoplasm there is one nucleus and chromatophores of a discoid, less often ribbon-like or lamellar form, vacuoles, in many types of pyrenoids.

Chromatophores of brown algae cells contain chlorophylls a and c, carotenes and several xanthophylls - fucoxanthin, violaxanthin, antheraxanthin and zeaxanthin. These pigments determine the brown color of algae. The stock products are the polysaccharide laminarin, the hexahydric alcohol mannitol, and lipids. In brown algae, both forms of reproduction occur: asexual and sexual.

Asexual reproduction is carried out by sections of the thallus. Some algae have specialized twigs (brood buds) that are easily detached and produce new plants. In addition, in most brown algae, asexual reproduction occurs through zoospores, in some representatives - tetraspores, and in single species - monospores. Zoospores develop in single- or multi-celled sporangia. The formation of spores is preceded by meiosis (with the exception of cyclospores, in which meiosis occurs before the formation of gametes).

The sexual process is iso-, hetero- and oogamous. With iso- or heterogamy, gametes are formed in multi-celled, multi-chamber gametangia, which can develop from one or many cells. In the most highly organized brown algae, the sexual process is oogamous. The egg is fertilized outside the oogonium. The zygote without a dormant period germinates into a diploid plant.

For most brown algae, a change in development forms is characteristic: for some it is isomorphic, for others it is heteromorphic. These different types of life cycle were previously used as the basis for dividing the Brown Algae into 3 classes: isogenerate with an isomorphic development cycle, heterogenerate with a heteromorphic development cycle, and cyclosporic with one Fucal order, where there is no alternation of generations. However, the division of brown algae into isogenerate and heterogeneous is rather arbitrary, since in both classes there are representatives with the opposite type of change in developmental forms. Therefore, a more correct approach to the classification of brown algae is considered to be dividing them into two classes - Phaeozoospores ( Phaeozaboutosporophyceae) and Cyclosporaceae ( Cyclosporophyceae).

Almost all brown algae live in the seas as benthic, epiphytic, or secondary planktonic organisms. Thickets of brown algae are food, breeding and sheltering places for many animal species, a substrate for micro- and macroorganisms, and one of the main sources of organic matter in temperate and subpolar latitudes. They are widely used in industry (food, perfume, textile) due to the presence of such valuable substances as alginic acid, alginate, mannitol, etc.

2.2.1 Class Phaeozoosporophyceous ( Phaeozoaboutsporophyceae)

Most algae of the Phaeozoosporophyceous class are characterized by 2 independent forms of development - sporophyte and gametophyte or gametosporophyte, which can be similar in appearance, structure and size and different, i.e. there is an isomorphic and heteromorphic change in the forms of development. In primitive representatives, there is no change in the forms of development.

The Phaeozoosporophyceous class is divided into 11 orders, of which 5 are given below.

Order Ectocarnal ( Ectocarpales). Includes brown algae, thalli (both sporophyte and gametophyte) of which are built from single-row filaments capable of branching. Their sizes vary from microscopic to 30 and more centimeters. These algae form plaque or bushes on rocks or other algae. They reproduce asexually and sexually. Reproductive organs are single and multi-nested receptacles. Uniloculars are always sporangia, while multiloculars can also function as gametangia.

Species of the genus Ectocarpus (ectocarpus) have a bushy thallus 0.1-30 cm high. It consists of thin single-row creeping and branching vertical threads. Filament growth is intercalary or diffuse. Attachment to the substrate is carried out by rhizoids, which in large specimens form a kind of bark at the base of the branches. To the top of the branches, the cells narrow and end in a long, colorless hair.

Sporangia and gametangia are arranged as lateral outgrowths of branches. Inside the unilocular sporangia, meiosis and mitosis occur, followed by the formation of biflagellated zoospores. Zoospores grow into haploid dioecious organisms with multi-celled gametangia. Gametes are isomorphic, but differ in behavior: the female loses mobility and releases an odorous substance that attracts male gametes, one of which fertilizes her. The zygote without a dormant period germinates into a diploid sporophyte.

Sfacelarial order ( Sphacelariales). Includes algae with hard bushy thalli from a few millimeters to 30 cm high; cylindrical branches. Unlike other brown algae, in sphacelial algae, each branch ends in a large cell, due to the division of which the algae have a strictly apical growth. Their thallus is characterized by a base in the form of a cortical plate of several layers of cells.

Vegetative reproduction occurs through stolons (filaments of several rows of cells creeping along the ground) or special brood buds that separate from the branches. Sphacelarians have an isomorphic change in the forms of development.

Seaweed sphacelaria genus (Sphacelaria) found in all seas. The thallus of its representatives has the appearance of a bush up to 4 cm high, consisting of a lamellar sole and branched threads extending from it. Each branching of the thread at the top carries a large cell, which divides only in the transverse direction and causes the growth of the thallus in length. The cells detached in this way are further divided in the longitudinal direction, due to which narrow cells are formed, and the thallus becomes multi-layered and outwardly consisting, as it were, of segments.

Cutlerial order ( Cutleriales). Includes brown algae, which are characterized by a trichothallic structure of the thallus due to the growth zone located in the basal part of multicellular hairs, which are located on the edges of the lamellar thallus or at the top of the branches of the bushy thallus. The cells of the growth zone divide, separating the cells towards the periphery and towards the thallus.

Dictyotal order ( Dictyotales). Combines species that are characterized by apical growth and usually dichotomous branching in the same plane. Asexual reproduction by means of aplanospores (tetraspores). The sexual process is oogamous. Change of forms of development is isomorphic. Most dictyotals grow in tropical and subtropical seas. Quite often they are found in the Black (species of the genera dictyota, dilofus and padina) and the Sea of ​​Japan (dictyota) seas.

Kinds kind of dictyota (Dictyota) are characterized by a forked-branched thallus with flat, usually located in the same plane branches without a longitudinal rib. The thallus develops from a cylindrical rhizome attached to the substrate by rhizoids. The top of each branch ends in one large cell . Inside the branches there is a layer of large colorless cells, surrounded on the outside by a bark of one layer of small intensely colored cells.

On sporophytes, sori of single-celled sporangia develop from surface cells, where four immobile tetraspores are formed. Tetraspores germinate into gametophytes. Dictyota is a dioecious algae: on the female gametophytes, sori of single-nested oogonia are formed with one egg in each. Antheridia are produced on male gametophytes. The eggs are released from the oogonium and are fertilized by spermatozoa in water. The zygote immediately germinates new organism- sporophyte. The most common dictyota is dichotomous (D. dichotoma).

Genus kelp (Laminaria) includes species whose thallus is divided into a leaf-shaped plate, trunk and rhizoids . Leaf-like plates are even or wrinkled, entire or dissected. The trunk and rhizoids are perennial, the leaf-shaped plate changes annually. On longitudinal sections from the petiole and organs of attachment, their rather complex anatomical structure is revealed. The outer part of the petiole is a cortex consisting of several layers of cells with chromatophores; the intermediate layer is represented by a large cell storage tissue and, finally, the inner (core) - conductive and mechanical. The conducting system includes tubular filaments with funnel-shaped extensions at the sites of cell walls. These partitions have pores and are called sieve plates, and the threads - sieve tubes . The petiole grows in thickness due to the division of the cells of the cortex, which occurs periodically, as a result of which concentric layers are clearly visible on the transverse section of the petiole, resembling the growth rings of higher plants.

During reproduction on the surface of the leaf-shaped plate of cortical cells, groups (sori) form unilocular zoosporangia, each of which forms from 16 to 128 two-flagellated zoospores. Under favorable conditions, zoospores germinate into microscopically small filamentous outgrowths - male and female gametophytes.

The sexual process in kelp is oogamous. The mature egg leaves the oogonium and attaches to its upper end. In this position, fertilization occurs. The zygote develops into a sporophyte without a dormant period. The female gametophyte provides not only the formation of germ cells, but also the place of attachment for the future sporophyte.

2.2.2 Class Cyclosporophycea ( FROMyclosporophyceae)

The Cyclosporophyceous class includes algae that do not have alternation of generations in the development cycle. Their diploid thalli bear only organs of sexual reproduction, which develop in special rounded receptacles - conceptacles, or scaphidia. Meiosis in cyclosporids occurs before the formation of gametes. There is no asexual reproduction by spores. All cyclosporophyces are large algae. Fucalia order (Fucales). Combines algae, which are characterized by a bushy form of thallus with apical growth. The cells of the axial parts of the thallus are weakly divided. They are elongated and form the core. genus fucus (Fucus) includes species with a flat, belt-like, dichotomously branched thallus up to 1 m long. A median vein runs along the lobes of the thallus with smooth or serrated edges, passing in the lower part into a petiole, which is attached to the substrate by a basal disc. In some types of fucus, air bubbles in the form of swellings are located on the sides of the midrib. The thallus grows due to the activity of the apical cells. During reproduction, the ends of the thallus swell, take on a light yellow-orange color and turn into receptacles, on which scaphidia with holes are formed. Between the paraphyses on the walls of the female scaphidium, oogonia are formed, while the male - antheridia. The zygote germinates without a dormant period. Fucus species are common along the coasts of the cold and temperate seas of the Northern Hemisphere, often forming large thickets in the intertidal zone, which facilitates their collection and use. Fucus species are used as fertilizers, livestock feed, feed flour, alginates and other chemicals. In the seas of Russia there are 5 species of this genus. The most famous F. vesiculosus (F. vesiculosus) and F. bilateral (F. distichus).

2.3 Department Red algae, or Crimson (RHODOPHYTA)

Representatives of the department in the overwhelming majority are multicellular organisms of a complex morphological and anatomical structure, and only a few, the most primitive, have a unicellular or colonial thallus of a coccoid structure. Many purple algae are large algae, reaching a length of several centimeters to two meters, but among them there are many microscopic forms.

In form, red algae are in the form of filaments, bushes, plates, bubbles, crusts, corals, etc. Lamellar forms reach a great variety. There are plates whole and complexly dissected, with additional outgrowths along the edge and on the surface. Some crimsons are highly calcified and resemble fossils.

With all the variety of external forms, red algae are characterized by a single structural plan of the thallus - it is based on a heterotrichous structure in all multicellular purple algae.

Branches of red algae fall into two categories. Some are the main long branches that grow in length during the entire period of plant growth, the so-called branches of unlimited growth. Others grow only up to a certain limit and always remain more or less short - these are branches of limited growth. In addition, they also have specialized branches that act as antennae, or rhizoids, which serve for additional attachment or adhesion to each other. The parenchymal type of organization is virtually absent. The only example of such a thallus is a representative of the class Bangiaceae (porphyry). In the majority of purple thalli, the pseudoparenchymal type (due to the interlacing of the branches of one axis - a uniaxial structure or many - multiaxial). The increase in the size of thalli in primitive forms is carried out due to diffuse cell division, in more organized ones, as a result of the division of apical cells, and in a number of species, due to the apical or marginal meristem. Organs of attachment to the substrate are rhizoids, suckers, soles or creeping rhizoidal plates.

The cells of red algae are covered with a membrane in which the inner, cellulose, and outer, pectin, mucilaginous layer are distinguishable. The agar-agar obtained from the latter contains, in addition to pectin, sugars and proteins. The casing can be impregnated with lime, magnesium or iron salts. The cytoplasm is distinguished by increased viscosity, adheres tightly to the walls, and is sensitive to changes in the salinity of the medium. In highly organized algae, the cells are multinucleated, in less organized ones, they are single-nuclear.

The shape of the chromatophores depends on the intensity of illumination, the size and age of the cells. However, the higher the organization of the alga, the more chromatophores in its cells and the more constant their shape (mainly lenticular). Pyrenoids are absent in many species. Like other algae, the color of plastids and the entire body of red algae is due to a combination of several pigments: chlorophylls a and d, phycobilins (phycocyanin, phycoerythrin, allophycocyanin) and carotenoids. The color of the thallus varies from crimson red (the predominance of phycoerythrin) to bluish-steel (with an excess of phycocyanin). The methods of reproduction of red algae are very diverse. Vegetative reproduction is peculiar only to primitive ones. It is carried out due to the formation of additional shoots, the growth of a new thallus from the sole of the old, dead, and also by cell division. Torn off sections of thalli die. Asexual reproduction is carried out by mono-, bi-, tetra- and polyspores formed in sporangia. Tetraspores are formed on diploid asexual plants - sporophytes (tetrasporophytes). In tetrasporangia, meiosis occurs before the formation of tetraspores.

The sexual process is oogamous. Karpogon usually consists of an expanded basal part - the abdomen (with a nucleus inside) and a tubular outgrowth - trichogyne, which receives sperm. Spermatangia are small colorless cells, the contents of which are released in the form of small, naked, devoid of flagella, male gametes - spermatozoa.

Fertilization of the egg is carried out by moving the sperm along the trichogyne into the carpogon. After fertilization, the basal part of the carpogon is separated by a septum from the trichogyne, which dies off and undergoes further development, leading to the formation of carpospores. The details of this development are important in the classification of purples. In some red algae, the contents of the zygote are divided with the formation of motionless naked spores - carpospores, in others, a system of special filaments is formed from the fertilized carpogon - gonimoblasts, the cells of which turn into carposporangia, producing one carpospore each. In most purple plants, the development of carpospores takes place with the participation of auxillary cells. In such cases, the gonimoblast develops not from the abdomen of the carpogon, but from the auxillary cell. If the auxillary cells are removed from the carpogon, connecting (oblastemic) threads grow from its abdomen after fertilization; their cells are diploid. The oblastemic filaments grow to the auxillary cells and dissolve at the point of their contact, after which plasmogamy occurs, resulting in the development of a gonimoblast with carpospores - a carposporophyte. Consequently, auxilary cells perform an auxiliary function - they stimulate the division of the cell nucleus of the connective thread and supply additional nutrition. In the most highly organized red algae (florideeficiaceae), auxilary cells develop after fertilization of carpogon in its immediate vicinity. Ooblastic filaments are not formed in these algae. The auxillary cell, located next to the abdomen of the carpogon, merges with it and forms a procarp.

The development cycles of red algae are varied. In some representatives of florideeficiaceae, there is a change in three forms of development: haploid gametophyte, diploid carpo- and tetrasporophyte. In this case, the zygote divides without reduction in the number of chromosomes, forming a sporophyte, on which, as a result of meiosis, tetraspores are formed, giving rise to gametophytes. Thus, there are two free-living forms of the same plant - tetrasporophyte and gametophyte. In other algae (with a heteromorphic change in developmental forms), the tetra- and carposporophyte is often poorly developed and even reduced, sometimes the gametophyte is reduced (it forms on the sporophyte).

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