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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 of various shapes and sizes, with a dense cell wall, single or connected in a colony (coenobia). 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 of a multicellular thallus and is a combination of immobile cells in filaments, 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 important role plays the presence in the shell, first pectin, and then cellulose fractions, providing supporting and protective functions, as well as the ability to permeability and growth. 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, while terrestrial algae can be collected from snow-free areas 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 in order to further study the collected material in a living state or with a 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 organic world taxonomists use a set of the most significant features of organisms included in a particular taxonomic category. These signs include:

1) historical development groups of living organisms according to 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 adverse conditions certain types cysts with a weakly silicified bivalve membrane are formed. 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 a stigma located on the anterior edge of the chromatophore, under its sheath. 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 high content 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 more high 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 ( PhaeozOosporophyceae) 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 ( PhaeozoOsporophyceae)

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 into a new organism - the 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 ( WITHyclosporophyceae)

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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Plant taxonomy
The foundations of taxonomy were laid by C. Linnaeus in the 18th century. In his works, Linnaeus defined the concept of "species", introduced a binary nomenclature, established a clear subordination between systematic categories; created a classification of plants and animals. The name of each species should consist of two words: one for the genus, both words for the species. In the taxonomy of plants, 7 categories (or taxa) are distinguished: kingdom, division, class, order, family, genus and species.

Seaweed
About 30 thousand species. Algae are lower plants, most of them live in aquatic environment. The body of algae is represented by a thallus, or thallus, not differentiated into organs and tissues. Some algae with the help of rhizoids (special outgrowths of cells) are attached to the substrate. The algal cell is characterized by the presence of a cell wall; inside contains one or more nuclei, vacuole, chromatophore and other organelles.

Department of green algae
This is the largest division of algae. Chlorophyll is characteristic, which prevails over other pigments. The reserve substance is starch.
Unicellular green algae
Chlamydomonas is a freshwater algae. There are two flagella, at their base there are two contractile vacuoles. Cupped chromatophore; in the cytoplasm there is one nucleus, an eye (stigma) and other organelles typical of eukaryotes. The peephole is used to perceive the level of illumination. Reproduction occurs asexually (occurs under favorable conditions with the help of haploid zoospores) and sexually (isogamy, under unfavorable conditions) by. After the formation of the zygote, it is covered with a thick shell and hibernates in this state. In the spring, meiosis occurs in it, the shell breaks and 4 young haploid individuals emerge from it.
Chlorella is an algae that can live in water, soil, soil surfaces, or tree bark in damp places. There are no flagella, ocellus and contractile vacuoles; inside the cell there is a nucleus, chromatophore and cytoplasm with organelles typical of plants. Reproduction is only asexual (using aplanospores), the sexual process is not known.
colonial green algae
Volvox is a freshwater algae. The colony looks like a hollow ball, the surface of which is formed by cells interconnected by cytoplasmic strands. Each cell contains one nucleus, chromatophore and 2 flagella. As a result of divisions of generative cells, daughter colonies are formed, which are located inside the mother, and after her death they go outside.
Multicellular green algae
Spirogyra is a filamentous freshwater algae. Outside, it is covered with a shell. Inside each cell are several threads of a spiral chromatophore, a nucleus and cytoplasm with organelles; Most of the cell is occupied by the central vacuole. Asexual reproduction occurs by filament fragmentation; sexual - conjugation. Special germ cells are not formed: two cells of different filaments merge with each other, and a zygote (diploid stage) appears.
Ulothrix is ​​a filamentous freshwater algae. Consists of one row of cells, with the help of a basal cell is attached to the substrate. The cell does not have flagella, contains one nucleus, a chromatophore in the form of a girdle and a vacuole. Reproduction is asexual and sexual. During asexual reproduction, zoospores are formed in the filament cell, then the shell is torn, and they come out. After swimming for some time, the zoospores settle and form a new thread by dividing. During sexual reproduction, isogametes are formed inside one of the cells, which go outside and merge in pairs. After the formation of the zygote, meiosis occurs, zoospores are formed, giving a new plant.

Department of brown algae
Mostly marine forms, predominantly common in cold seas. Most brown algae are benthic forms that live at depths of 20-30 miles in the intertidal zone. Can form huge aggregations (Sargasso Sea).
The color varies from olive green to dark brown due to the presence of the brown pigment fucoxanthin, which masks other pigments. They also contain chlorophyll and carotenoids. The thallus is multicellular, ribbon-like (kelp), bushy (sargasso) or branched (fucus), usually attached to the substrate with the help of rhizoids.

Department of red algae (crimson)
Red algae live mainly in the seas, freshwater forms are less common. They inhabit significant depths (up to 260 m - an absolute record for photosynthetic plants). There are unicellular and multicellular forms. They contain chlorophyll, carotenoids and phycobilins (red pigments). Thallus filiform, bushy, lamellar (porphyry), in some dissected; many have rhizoids. The cell membrane is covered with a layer of pectins, from which agar-agar is obtained.

The value of algae in nature and their use by humans

• Give off oxygen.
• Food chains (phytoplankton are the basis of all ocean grazing chains).
• Shelter for animals.
• With mass reproduction, they cause "blooming" of water (chlamydomonas), in which the oxygen content in the water drops.
• Some species (chlorella) are used on spaceships and submarines to clean the air from carbon dioxide.
• Food (kelp, porphyry). Some algae are specially grown on underwater farms.
• Feed (fucus, chlorella).
• source of iodine.
• Industrial: obtaining sodium and potassium salts, agar-agar. Jelly, marmalade, marshmallow, a nutrient medium for growing bacteria are made from agar-agar.

1.4. DEPARTMENT OF CYANOBACTERIA (CYAN ABOUT BACTERIA), OR BLUE-GREEN ALGAE (CYANOPHYTA)

Cyanobacteria, or blue-green algae (or cyanes), are the most ancient, morphologically and physiologically unique group of organisms. Many properties of blue-green algae (nitrogen fixation, intravital release of organic substances, oxygenic type of photosynthesis) determine their extremely important role in soil and water bodies. Recently, cyanoeas have become objects of research by biochemists and physiologists, hydro- and microbiologists, geneticists and plant growers, as well as specialists in space biology.

The department includes unicellular, colonial and multicellular (filamentous), from microscopic to visible to the naked eye organisms of various morphological structures. Colonial forms exist throughout life or at separate stages of development of the alga. Multicellular cyanideas live in separate threads or are collected in sods. They have symmetrical or asymmetrical, simple or branched trichomes (bodies), intercalary or apical growth zones. A number of filamentous cyanides have specialized cells - heterocysts with strongly thickened colorless two-layer shells. They take part in the process of atmospheric nitrogen fixation.

The cell is dressed in a pectin membrane of complex structure and composition, often mucilaginous, under which there is a protoplast, usually devoid of vacuoles with cell sap. The cell lacks a separate nucleus, chromatophores, Golgi apparatus, mitochondria, and endoplasmic reticulum.

The cytoplasm is divided into the central part - the centroplasm (nucleoplasm) and the colored peripheral part - the chromatoplasm. The structure of the centroplasm - an analogue of the nucleus in blue-green algae - is close to identical structures bacterial cells and differs significantly from the structure of cells with formed nuclei.

Photosynthetic lamellar structures and pigments are located in the chromatoplasm: chlorophyll a, carotenoids and bilichromoproteins (blue phycocyanin and allophycocyanin and red phycoerythrin) red algae). Due to the unique and labile composition of pigments, cyanide is capable of absorbing light of various wavelengths.

Reserve substances are represented by glycogen, volutin, cyanophycin grains. Many blue-green algae have gas vacuoles in their cytoplasm.

Cyanides reproduce by simple binary cell division, the collapse of colonies, fragmentation of threads into separate sections of the thallus - hormogony, capable of germinating into new thalli, as well as gonidia, cocci, planococci. Gonidia - small cells with a mucous membrane, separated from the thallus or located inside the endospores.

cocci - unicellular fragments of the thallus that do not have a clearly defined shell.

Planococci - small naked cells capable of independent movement.

Many filamentous cyanides form spores (akinetes) from one, and sometimes from two or more adjacent vegetative cells, which serve mainly to endure unfavorable conditions. Sporulation is characteristic of Nostoc and Chamesiphon, the latter form exo- and endospores that serve for reproduction.

The sexual process and mobile flagellar forms and stages of development in cyanobacteria have not been identified.

Blue-green algae are common in fresh and salt waters, on the surface of the soil, rocks, in hot springs, and are part of lichens. Together with bacteria cyanide enrich the soil with organic matter and nitrogen, contribute to the eutrophication of water bodies, are food for zooplankton and fish, can be used to obtain a number of valuable substances produced by them in the course of their vital activity (amino acids, vitamin B 12 , pigments, etc.) During the period of mass reproduction in reservoirs, the so-called "bloom" of water, some cyanides are toxic to aquatic animals. Some species can be used for food.

Blue-green algae are divided into 3 classes: Chroococcophyceous, Hamesiphonophyceous and Hormogoniophyceous. The classification is based on the structural features of the thallus and the reproduction of cyanide.

Class Chroococcophytes ( Chroococcophyceae)

The class includes colonial and unicellular organisms. Colonies are formed mainly by cells that have not dispersed after division, less often by their adhesion. The cells in the colony are arranged mostly randomly. They are not differentiated into bottoms and tops. They reproduce vegetatively. Heterocysts, as well as endo- and exospores are absent. There are 2 orders and 35 genera in a class.

Order Chroococcal (Chroococcales). It combines widespread unicellular and colonial forms, free-floating or lying on the substrate. Some representatives lead an attached lifestyle.

Genus Microcystis (Microcystis)- These are microscopic, as a rule, shapeless lumps of mucus, in which randomly located small spherical cells are immersed. In many species, cells appear almost black under a microscope due to the abundance of gas vacuoles in them, due to which

nii float to the surface of the water. The outlines of the mucus of this colony can be very diverse, and sometimes peculiar cells appear in the mucus, due to which the colonies become reticulated (Fig. 1.1).

About 25 species are known, distributed in fresh and marine waters, as well as in the soil. In Belarus, 19 species and 26 varieties* have been identified. Found in reservoirs, lakes and rivers. The most common M. bluish-green (M. aeruginosa), M. Greville (M grevillei) and M. powdery (M pulverea). Some species are toxic.

Class Hormogoniophyceous ( Hormogoniophyceae)

The class includes multicellular algae of a filamentous or trichome form, in which the protoplasts of neighboring cells are interconnected by plasmodesmata. Trichomes are naked or covered with mucous sheaths. Many of them are characterized by heterocysts. Reproduction occurs by hormogonia, less often by akinetes. The class has over 10 orders. The most important of them are oscillatory and nostocal.

Order Oscillatory(Oscillatoriales). Includes species that have single-row homocytic trichomes, which consist of the same cells, with the exception of the apical one. Trichomes do not have heterocysts and are almost always devoid of spores, often mobile in a vegetative state.

Most of the filamentous blue-green algae belong to this order.

Genus Oscillatoria (Oscillatoria) includes species that often form blue-green films that cover wet ground after rain, underwater objects and plants, drag the muddy bottom and water surface of stagnant reservoirs.

The oscillator is a long blue-green filament. Looking at the end of the thread under a microscope, you can see it oscillatory movements. This oscillation is accompanied by the rotation of the thread around its own axis and its translational movement.

With a high magnification of the microscope, it can be seen that the threads are made up of identical cylindrical cells, with the exception of the apical ones, which are somewhat different in shape from the rest (Fig. 1.2).

Inside the cell, one can see granular inclusions - cyanophycin grains, located, as a rule, along the transverse partitions. The thread multiplies by breaking up into separate sections - hormogonia, growing into new threads.

More than 100 species are known. In Belarus, 39 species and 49 varieties have been identified. They live in the benthos and plankton of mainly fresh water bodies, sometimes causing them to "bloom". Attached to underwater objects. Live in the silt

wet sand or soil, and are also found in sewage. The most common in the plankton of ponds and lakes: O. lake ( O. limnetica), O. planktonic (O. planctonica), O. muddy (O. limosa), O. thin (O. tenuis). O. slender is found everywhere on piles, stones, and the surface of still waters. (O. formosa).

Nostocal order(Nostocales). It combines hormogonian algae with heterocytic unbranched filaments or filaments with false branching (due to the breakthrough of the trichomes to the side), often with akinetes. Trichomes come with or without sheaths.

Genus Anabena (Anabaena) of the family of the same name is represented by single or irregular clusters of trichomes. Trichomes are symmetrical, consisting of round or barrel-shaped vegetative cells with intermediate heterocysts, mostly free-floating, straight or curved. Anabena species are found both in plankton and in benthos. Reproduction is carried out by hormogonia, into which the threads break down, as a rule, along heterocysts. Hormogonia grow only due to transverse cell divisions. In addition, in these algae, individual vegetative cells, due to strong growth, turn into akinetes (Fig. 1.3). Akinetes are much larger than vegetative cells and are distinguished by their bright blue-green color against the background of other cells almost black from gas vacuoles. The contents of the akinetes are usually granular, which in most cases is due to the accumulation of cyanophycin grains. About 100 species are known, 28 of them are in Belarus. They are found in fresh water plankton, some in brackish water and on moist soil. The most common A. Gassala (A. hassalii), A. Sheremetyeva (A. scheremetievii), A. changeable (A. variabilis), A. spiral (A. spiroides), A. "blooming" water (A.flos-aquae) and etc.

Genus Nostoc (Nostoc) characterized by complex mucous or gelatinous colonies of various sizes (from microscopically small to large, reaching the size of a plum) and shape, often spherical. In the mucus there are intricately intertwined threads, similar to the threads of anabaena. Reproduces by hormogonia. They become mobile and leave the mother colony, the mucus of which is blurred by this time. After a certain period of movement, the hormogonia stop, lose their gas vacuoles (in benthic species), and grow into spirally twisted filaments. Then, as a result of repeated divisions of hormogony cells, a zigzag thread is formed by longitudinal or oblique partitions, which is characteristic of nostocs. These threads are covered with abundant mucus and thus a young colony appears (Fig. 1.4). Sporulation is also observed, in which many vegetative cells turn into akinetes, usually little different in shape and size from vegetative cells.

Nostok species (more than 50, including 8 in Belarus) are widespread in water bodies and on soil. Some species are edible. A typical representative of the genus - N. plum-shaped (N. pruniforme), listed in the Red Book of the Republic of Belarus.

Genus Gleotrichia (Gloeotrichia) includes species in which the threads are connected by a common mucus into spherical or hemispherical colonies. Asymmetrical string-like filaments inside the mucus are located radially, have widened ends, bearing heterocysts and akinetes facing the inside of the colony (Fig. 1.5). Reproduces by hormogonia. 15 species are known, including 3 in Belarus. They are found mainly in stagnant fresh water bodies; first attached to the substrate, then swim freely; of these, only two species are planktonic organisms. Widespread G. floating ( G. natans) and G. pisiform (G. pisum).

Tasks

1. Consider and draw a general view of a microcystis colony, several individual cells with gas vacuoles.

2. Place a drop from a bottle with an oscillatorium on a glass slide and examine it under a microscope, first at low magnification, then at high magnification. Draw part of the trichome. Note the cylindrical shape of the vegetative cells, the rounded shape of the apical cells, the thin pectin membrane, the strongly colored peripheral layer of the cytoplasm - the chromatoplasm and the lighter centroplasm, the grains of cyanophycin.

3. Consider and draw the thread of the anabaena. Mark vegetative cells with gas vacuoles, heterocysts and akinetes.

4. With dissecting needles, separate a piece of mucus from the peripheral part of the nostoc colony, place it in a drop of water on a glass slide and examine it under a microscope. Draw a general view of a part of the colony at low magnification and a separate thread at high magnification. Note vegetative cells and heterocysts.

5. Consider and draw a colony of gleotrichia. Then destroy the colony, take a piece of mucus containing gleotrichia filaments, and examine it under a microscope. Note that the heterocyst lies at the base of the thread. The cells that make up the thread, as they move away from the heterocyst, become thinner and at the top turn into a colorless hair.

Questions for self-control

1. How do cyanobacteria differ from phototrophic green and purple bacteria in terms of body structure, pigment set, and type of photosynthesis?

2. How does the cell structure of blue-green algae differ from the cell structure of other organisms?

3. What forms of thallus organization and reproduction are known in cyanide?

4. What pigments and reserve products are noted in the cells of blue-green algae?

5. What is the uniqueness of the photosynthetic apparatus of blue-green algae?

6. What are the features of the structure and function of heterocysts and akinetes?

7. What is the importance of blue-green algae in nature and national economy?

1.5. DEPARTMENT OF EUGLENIC ALGAE (EUGLENOPHYTA)

The department includes microscopic unicellular organisms equipped with one or two flagella and actively moving. The body shape of euglena algae is elongated, oval, elliptical or fusiform. There is no cellulose shell; its role is played by the outer compacted layer of the cytoplasm - the pellicle. Those species in which the pellicle is soft, elastic, have the ability to change the shape of the body. Few algae have a hard outer shell, usually impregnated with iron salts, which does not adhere tightly to the protoplast. The number and shape of chromatophores are different. They are spindle-shaped, ribbon-shaped, disc-shaped, stellate, lamellar. The green color of eugleno algae is due to the presence of chlorophylls. A And b. In addition to them, there are carotenes and xanthophylls. The reserve product is paramylon, a derivative of glucose; it is deposited on the outer parts of the pyrenoids protruding from the chromatophores in the form of shells or in the cytoplasm in the form of small grains.

At the anterior end of euglenoids is a depression, often called the pharynx. It is the output end for the system of contractile vacuoles, in which fluid accumulates with dissolved metabolic products.

The movement of euglena algae is carried out due to metabolic changes in the shape of the body and with the help of a flagellum.

Reproduction occurs by longitudinal division of the cell in half in a mobile or immobile state. Under unfavorable conditions, some euglena algae form dormant cysts with thick shells. The sexual process has not been proven.

Euglena algae are common inhabitants of small fresh stagnant water bodies, causing a “bloom” of water during mass development. This group of plants is characterized by all three main types of nutrition: phototrophic, saprotrophic and holozoic (ingestion of formed particles of organic matter or small organisms), sometimes mixed (mixotrophic).

The department includes class 1 Euglenophycia.

Class Euglenophycia (Euglenophyceae)

The class combines several orders, the differences between which are based mainly on the details of the structure of the flagellar apparatus.

Representatives of the order Euglenales (Euglenales) can serve as the genera Euglena, Trachelomonas and Facus.

Algae genus Euglena (Euglena) cells are motile, spindle-, ovoid- and ribbon-shaped, cylindrical, more or less spirally twisted. The anterior end is narrowed and rounded, the posterior end is pointed, rarely rounded or with a narrow styloid process (Fig. 1.6). At the anterior end of the cell there is a stigma, pulsating vacuoles and a pharyngeal opening, from which one of the flagella emerges, and the second, short, is located inside the pharynx. Single nucleus, one to several chromatophores, with or without pyrenoids.

155 species are known, distributed mainly in small fresh water bodies (puddles, lakes, rivers), swamps, and on wet soil. Some species cause the water to "bloom" green or red. 25 species are known in Belarus. Often found E. green ( E. viridis), E. spirogyra (E. spirogyra), E. needle (£. acus), E. caudate (E. caudata) and others. Euglenophytes can serve as indicators of water quality.

includes free-swimming organisms with a flagellum and a solid house. The structure of the house is hallmark kind. The houses have a different shape, as a rule, they are brown in color and in front there is a hole for the tourniquet to exit (Fig. 1.7). The walls are smooth or with pores, papillae, granules, spines. Chromatophores (two or more) green, with or without pyrenoids. There are species without chlorophyll - saprotrophs. During reproduction, the cell divides inside the house: one of the daughter individuals slips out through the hole and develops a new house.

About 200 species are known, in Belarus there are 57 and 84 varieties, common in shallow water bodies with fresh water. The most famous T. volvox ( T. volvocina), T. small-bristle (T. hispida), T. armed (T. armata), T. oblong (T. oblonga), T. ovoid (T. ovata) and etc.

Species genus Facus (Phacus)(Fig. 1.8) cells are flattened, more or less corkscrew-shaped, asymmetrical, ovoid, oval or spherical, with one flagellum, often with a colorless steering process at the posterior end of the body. The pellicle is dense, colorless, with streaks or rows of granules, papillae, or spines. Chromatophores numerous, small, discoid, near-wall, without pyrenoids. The nucleus is one (usually in the back of the cell). The protoplast contains paramylon grains.

About 140 species are known, distributed in shallow stagnant water bodies or in the coastal part of lakes and rivers polluted with organic substances. In Belarus, there are 18 species and 27 varieties. The most common F. longtail (Ph. longicauda), F. fine bubble (Ph. vesiculosum), F. round (Ph. orbicularis), F. caudate (Ph. caudatus) and etc.

Exercise

Examine at high magnification of the microscope and draw the cells of euglena, phacus and trachelomonas. Note the structural features of the house, a colorless straight process at the phacus and a neck or funnel in trachelomonas, a nucleus, chromatophores, a flagellum at the anterior end of the body. (To see the flagella, stain the slide with 2% methylene blue or iodine in potassium iodide.)

Questions for self-control

1. What are the features of the structure and lifestyle of euglena algae?

2. What is the significance of some representatives of euglena algae for characterizing the degree of water pollution?

3. In what cases do euglena algae switch to a mixotrophic mode of nutrition?

1.6. DIVINOPHYTE ALGAE DEPARTMENT (DINOPHYTA)

Most dinophyte algae have a monadic structure and are represented by single cells. Less common are amoeboid, palmelloid, coccoid and filamentous forms. They are characterized by a dorsoventral body shape: the dorsal and ventral sides are clearly expressed in the structure of the cells, the difference between the anterior and posterior ends of the body is clearly visible.

An important feature for all dinophytes is also the presence of two grooves in the cells. One of them - transverse - covers the cell in a ring or spiral, but does not close completely, the other - longitudinal - is located on the ventral side of the cell.

The cell cover in the most primitive forms is represented by a smooth thin periplast(spherical shapes). Most dinophytes are covered current, consisting of cyto- plasma membrane, under which the components of the theca are located in one layer - flattened blisters (vesicles, cisterns) surrounded by a membrane.

Two flagella different in length, structure, and even functions (one of them is swimming, the other is steering) are attached on the ventral side; one is almost completely hidden in the transverse groove, the other protrudes from the longitudinal groove and is directed along the backward movement of the cell. Many unicellular algae have a so-called pharynx (a kind of tube) and special mucous bodies that strongly refract light - trichocysts, located in the peripheral layer of the cytoplasm or in longitudinal rows on the inner surface of the pharynx. Contacting during movement with another algae or grain of sand, trichocysts are ejected in the form of long mucous threads, causing an abrupt movement of the cell.

Dinophyte algae are characterized by the so-called mesokaryotic type of cell organization with a nuclear apparatus, which still retains the features of some primitiveness. This is expressed in the chemical composition of chromosomes (absence of histones) and their behavior during mitosis, the phases of which are atypical; in particular, chromosomes that are poorly differentiated in length due to the absence of centromeres are constantly in a condensed state and are preserved in the interphase nucleus. There may be one or more nucleoli in the nucleus, which usually disappear during division. During mitosis, the nuclear envelope does not disappear and the fission spindle does not form.

The protoplast contains chromatophores of various colors (olive, brown or brown, yellow, golden, red, blue, blue). The color is due to the presence of chlorophylls a and c, carotenes a, , synthesizing organic matter(for comparison, higher plants are able to absorb only 1-2% of solar radiation) to create a cycle of things