Projects, diagrams, drawings
Zoospores of yellow-green algae drawing. Lecture: Department of yellow-green or heteroflagellate algae

Zoospores of yellow-green algae drawing. Lecture: Department of yellow-green or heteroflagellate algae

Plan:

1 Cell structure
- 1.1 Flagella
- 1.2 Chloroplast
- 1.3 Cell wall
- 1.4 Other structures
- 1.5 Core
2 Reproduction
3 Ecology
4 Meaning
5 Phylogeny
6 Diversity and systematics

Introduction

Yellow-green algae(lat. Xanthophyceae, or Xanthophyta), or Multiflagellate algae(lat. Heterocontae), or Tribophyceae(lat. Tribophyceae) - a class of lower plants, including algae, the chloroplasts of which are colored yellow-green or yellow. Representatives are unicellular, colonial and multicellular, mainly freshwater organisms. Similar to golden algae, the division of yellow-green algae into classes is based on the diversity of the morphological organization of the thallus. Class named after type genus Tribonema(from Greek tribe- experienced, skillful, nema- a thread).

1. Cell structure

1.1. Flagella

Monad representatives (zoospores and gametes) have two flagella of unequal length and morphology: the main flagellum has feathery ciliated hairs, the lateral flagellum is whip-shaped. The exception is synzoospores Vaucheria, in which numerous pairs of smooth flagella of slightly different lengths are located on the surface. Flagella are attached subapically to the cell (in sperm Vaucheria lateral attachment). Mastigonemes are synthesized in the cisterns of the endoplasmic reticulum. The short flagellum ends with an acroneme.

The basal bodies of tribophycean flagella have a typical structure, located at right angles to each other. The radicular system is represented by a cross-striated root - rhizoplast and three microtubular roots, each of which consists of 3-4 microtubules.

1.2. Chloroplast

The chloroplast has a structure typical of ochrophytes. Typically, a cell contains several green or yellow-green disc-shaped plastids. Their color is due to the absence of fucoxanthin, which is responsible for the golden and brown color of other ochrophytes. Of the carotenoids in Tribophyceae, there are α- and β-carotenes (predominant), voucheriaxanthin, diatoxanthin, diadinoxanthin, heteroxanthin, lutein, violaxanthin, neoxanthin, etc. Chlorophylls - a And c. In the cells of Tribophyceae, in addition to disc-shaped ones, there are plastids of other forms: lamellar, trough-shaped, ribbon-shaped, cup-shaped, stellate, etc. In a few species, pyrenoids of the semi-constricted type were found. The ocellus consists of a number of lipid globules, located at the anterior end of the body in the chloroplast, oriented towards the basal swelling of the flagellum.

1.3. Cell wall

Species with amoeboid, monadic and palmelloid organization lack a cell wall, they are covered only by a cytoplasmic membrane and can easily change shape. Sometimes “naked” cells are located inside houses, the walls of which can be painted brown with manganese and iron salts. The vast majority of tribophyceae have a cell wall that is solid or consisting of two parts. In its composition, studied by Tribonema And Vaucheria, cellulose predominates and contains polysaccharides consisting mainly of glucose and uronic acids. Young cells have a thin membrane, but with age it thickens. Iron salts can be deposited in it, the compounds of which color it in various shades of brown and red. Most often, silica is present in the cell wall, giving it hardness and shine. It can also be inlaid with lime and be sculptured in various ways (spines, cells, warts, bristles, denticles, etc.). In attached forms, an outgrowth of the shell may form - a leg with an attaching sole.

In filamentous algae with bivalve membranes, when the filaments disintegrate, the cell membranes fall apart into H-shaped fragments, which are tightly connected halves of the membranes of two neighboring cells. As filaments grow, an H-shaped fragment of the cell wall of two adjacent daughter cells is inserted between the two halves of the mother cell wall. As a result, each of the daughter cells is half covered with the old membrane of the mother cell and half with the newly formed membrane.

1.4. Other structures

Contractile vacuoles are present in motile representatives. Usually there are 1-2 of them per cell, sometimes more. The Golgi apparatus has a unique structure. Dictyosomes are small, containing 3-7 cisternae.

Reserve nutrients are oils, some have volutin, chrysolamine and leukosin.

1.5. Core

There is one nucleus, less often there are many nuclei; in coenotic representatives the cells are always multinucleated. The details of mitosis have been studied in detail only in Vaucheria. Its mitosis is closed, with centrioles located at the poles outside the nucleus. No kinetochores were found. During anaphase, the interpolar microtubules of the spindle greatly elongate, which leads to a significant distance between the daughter nuclei and each other. The nuclear membrane is preserved, so in telophase the daughter nuclei have the shape of a dumbbell. It is believed that such mitosis is not typical for the entire group of Tribophyceae.

2. Reproduction

Most yellow-greens have known vegetative and asexual reproduction. Vegetative propagation is carried out by dividing cells in half, disintegrating colonies and multicellular thalli into parts. During asexual reproduction, amoeboids, zoospores, synzoospores, hemizoospores, hemiautospores, autospores, and aplanospores can be formed. Zoospores are “naked” and usually pear-shaped with two flagella. The sexual process (iso-, hetero- and oogamous) is described in a few representatives.

When unfavorable conditions occur, the formation of cysts is observed. Cysts (statospores) are endogenous, mononuclear, less often multinucleate. Their wall often contains silica and consists of two unequal, or less often, equal parts.

3. Ecology

Tribophyceae are found on all continents, including Antarctica. They live mainly in fresh waters of temperate latitudes, are also common in soil, and are less common in terrestrial, brackish-water and marine habitats. They inhabit both clean and polluted waters, with varying pH values, but are rarely found in abundance. Tribofyceous algae are significantly more diverse and abundant in soils, where, developing in masses, they can cause a “blooming” of the soil surface. Aerophytic representatives are found on tree trunks, rocks, and walls of houses, sometimes causing them to turn green. They often live in accumulations of filamentous algae and aquatic higher plants along the banks of rivers, ponds, lakes and reservoirs.

Yellow-green algae are included in various ecological groups - plankton, less often periphyton and benthos. The vast majority of them are free-living forms, but intracellular symbionts - zooxanthellae - are also found in protozoan cells. Seaweed chloroplasts form an interesting intracellular symbiosis V. litorea with clam Elysia chlorotica. For 9 months, this mollusk is capable of photoautotrophic carbon dioxide fixation in culture. This is the longest symbiosis of this type, when the symbiotic plastid is in direct contact with the cytoplasm of the animal. In nature, mollusk larvae feed on threads Vaucheria. As a result of phagocytosis, algae chloroplasts enter the cytoplasm of the mollusk epithelial cells. During this process, the chloroplast envelope becomes three-layered, and the outer membrane of the chloroplast endoplasmic reticulum is lost. This phenomenon can serve as evidence that in the process of evolution, as a result of secondary symbiogenesis due to the loss of membranes, chloroplasts with three membranes could arise.

4. Meaning

Tribophycean algae are producers of oxygen and organic substances and are part of trophic chains. They participate in the self-purification of polluted waters and soils, the formation of silts and sapropels, and the process of accumulation of organic substances in the soil, affecting its fertility. Their economic importance comes down to their use as indicator organisms in determining the state of water pollution; they are part of a complex of microorganisms used for wastewater treatment.

5. Phylogeny

At the end of the 19th - beginning of the 20th centuries. various genera of Tribophyceae were classified as green algae, which was primarily due to the color and morphological similarity of the thalli. But A. Pascher already included this group in the same evolutionary series with golden algae and diatoms. This point of view was subsequently confirmed by studies at the cytological, biochemical and molecular level. Currently, Tribophyceae are considered as a class within the Ochrophytae division. From tribophyceae, eustigmatophyceae were isolated in the rank of the same class, but, as it turned out, in evolutionary terms they are far from each other. In phylogenetic trees built on the analysis of nucleotide sequences of a number of genes, tribophyceae among ochrophytes are much closer to brown algae than to golden algae, diatoms, sinuraceae and eustigmatophyceae.

6. Diversity and systematics

About 90 genera and more than 600 species have been described, which are grouped into 6-7 orders (H. Ettl, 1978). The identification of orders is based on the type of differentiation of the thallus and the characteristics of the life cycle. The number of orders depends on the point of view on coenotic tribophycean algae: whether they are classified as one or two orders.

Notes

According to EOL. See card.

Literature

Plant life. In 6 volumes / Ch. ed. Al. A. Fedorov. - M.: Education, 1977. - T. 3. Seaweed. Lichens. Ed. M. M. Gollerbach. - 487 p. - 300,000 copies.
"Course of lower plants", ed. M. V. Gorlenko - M.: “Higher School”, 1981
V. A. Kryzhanovsky, G. L. Bilich “Biology. Full course. In 3 vols. Volume 2. Botany." - M.: LLC Publishing House "ONICS 21st Century", 2002
“Small workshop on lower plants” - M.: “Higher School”, 1976
N. P. Gorbunova “Algology”, M.: “Higher School”, 1991

The yellow-green department includes algae whose chloroplasts are colored light or dark yellow, very rarely green and only sometimes blue. This color is determined by the presence of the main pigments in the chloroplasts - chlorophyll, carotenes and xanthophylls. However, in the chloroplasts of yellow-green algae, carotenes always predominate, which determines the originality of their color. In addition, their cells lack starch, and droplets of oil accumulate as the main assimilation product, and only in some, in addition, lumps of leukosin and volutin.

Yellow-green algae are characterized by great morphological diversity. Among their many representatives, almost all the main types of algae body structure are found: amoeboid, monadic, palmelloid, coccoid, filamentous, heterofilamentous, lamellar and siphonal.

Yellow-green algae are distributed throughout the globe. They are found mainly in clean freshwater bodies of water, less often in seas and brackish waters, they are also common in soil; can live in both acidic and alkaline waters; preferring moderate temperatures, they most often develop in spring and autumn, although there are species found throughout all periods of the year, including winter.

Yellow-green algae are mainly representatives of plankton, mainly passive plankters; they are less common in the periphytope and benthos. Most often they can be found in accumulations of filamentous plants and among thickets of higher aquatic plants in the coastal zone of rivers, ponds, lakes and reservoirs, less often in clear water.

, ,
, ,

Among the yellow-green algae there are representatives with a thallus of unicellular (Fig. 188, 1, 2, 5; 190; 191), colonial (Fig. 189), multicellular (Fig. 192, 1, 2) and noncellular structure (Fig. 192 , 3). In addition, very peculiar algae with a multinucleate thallus in the form of naked plasmodium are known here (Fig. 188, 3).

Regardless of the external structure, the internal structure of the cell of yellow-green algae is quite uniform. In the protoplast, several yellow-green chloroplasts are usually observed, having a disc-shaped, trough-shaped, lamellar, less often ribbon-shaped, stellate or cup-shaped with solid or lobed edges. In motile forms, a red eye is usually located at the anterior end of the chloroplast. A few species usually have a two-shelled pyrenoid. There is one nucleus in a cell, usually small in size, noticeable only after treating the cell with special dyes, but there are also species with multinucleated cells.

In a small number of species, the morphologically anterior part of the cell has one or two pulsating vacuoles.

A distinctive feature of yellow-green algae is the presence of two unequal flagella in vegetative cells of a monadic structure and zoospores. It was this feature that at one time served as the basis for naming this group of algae heteroflagellates, or heterokonts(Heterocontae). In addition to differences in length, the flagella here also differ morphologically: the main flagella consists of an axis and ciliated hairs pinnately located on it, the lateral flagella is whip-shaped.

In contrast to the internal contents of the cell, its shell in yellow-green algae shows significant diversity. In the simplest representatives, the cell is surrounded only by a thin and delicate periplast, allowing it to produce protrusions in the form of pseudo- and rhizopodia (Fig. 188, 1 - 4). But in most species the cell is covered with a real dense membrane, which determines the constant shape of the body. This shell can be solid or bicuspid, with valves of equal or unequal size. In most representatives, the valves are usually difficult to distinguish; they become clearly visible only under the influence of a 60% solution of caustic potassium or when stained.

Usually the shell is colorless, transparent, less often colored brown or yellowish. In many representatives it has various sculptural decorations and can be inlaid with lime, silica or iron salts.

Yellow-green algae reproduce by simple cell division or the disintegration of colonies and multicellular thalli into separate parts. Asexual reproduction is also observed with the help of biflagellate zoospores or autospores, less commonly, amoeboids. The sexual process is known in few species and is represented by iso- and oogamy. In some species, in the development cycle, exo- and endogenous cysts with a bivalve, often silicified shell are known (Fig. 189, 3).

The importance of yellow-green algae as phototrophic organisms lies primarily in the creation of primary production in water bodies and their participation in the food chain of aquatic organisms. Yellow-green algae, along with many others, form sapropel (silt). Living in bodies of water rich in organic residues, they can serve as indicative forms in determining the degree of water pollution. In soils, they actively participate in the accumulation of organic matter, helping to increase fertility.

Yellow-green algae are a group that has not yet been sufficiently studied. Its origin has not been reliably determined. At present, the prevailing opinion is that they are an independent department, since they show a clearly defined parallelism of forms with golden and green algae, the separation of which into independent departments no one doubts. Undoubtedly, yellow-green algae are related to golden algae and diatoms.

According to the latest data, the department of yellow-green algae (Xanthophyta) can be divided into six classes: xanthopodaceae(Xanthopodophyceae), xanthomonas(Hapthomonadophyceae), xanthocapsaceae(Xanthocapsophyceae), xanthococcal(Xanthococcophyceae), xanthotrichaceae(Xanthotrichophyceae) and xanthosiphonaceae(Xanthosiphonophyceae).

Life of plants: in 6 volumes. - M.: Enlightenment. Edited by A. L. Takhtadzhyan, editor-in-chief, corresponding member. USSR Academy of Sciences, prof. A.A. Fedorov. 1974 .

These algae contain, in addition to chlorophyll, yellow pigments - xanthophyll and carotene; their color varies from light to dark yellow-green. less often green and for some – blue. Representative: botridium.

Yellow-green algae are organisms at different stages of morphological differentiation of the thallus, – unicellular, colonial and multicellular. Among them there are predominantly coccoid, palmelloid or filamentous structures, less often – amoeboid, monadic, siphonal, heterofilamentous and lamellar.

Motile forms of yellow-green algae (including zoospores) are characterized by the presence of two flagella of unequal size (lateral – short, flagellated and anterior – long with mastigonemes) and yellow-green color of chromatophores. Spare products – volutin, fat, often chrysolamine. In primitive forms, the cell contents are surrounded by a thin periplast, while in more highly organized representatives there is a pectin or cellulose shell (solid or bicuspid). The cell membrane is often impregnated with iron salts, silica, lime, and has various “sculptural decorations”.

The protoplast of a cell contains several chromatophores, which can be disc-shaped, plate-shaped, ribbon- or cup-shaped or star-shaped. One or many cores. Some species have pyrenoids. Stigma is noted in mobile forms.

Yellow-green algae can reproduce by longitudinal cell division, the disintegration of colonies or filaments into separate sections, and also by zoo- or aplanospores. The sexual process (iso- or oogamy) is known to few. To withstand unfavorable conditions, some species form cysts with a slightly silicified bivalve shell.

The department includes 2500 species. Representatives of the department are widespread in various habitats, especially in clean fresh water bodies; they are also common in soil. These algae are mainly passive plankters. More often they can be found in accumulations of filamentous algae and among aquatic plants.

These are predominantly microscopic unicellular algae, including colonial, multicellular and noncellular.

The predominant type of thallus structure is coccoid. Monadic, amoeboid, coccoid, palmelloid, filamentous, lamellar and siphonal.

Motile forms and stages have two flagella. Characteristics of flagella.

Outer covers: Some cells are covered only with plasmalemma - these are all amoeboid forms, some are monadic. They form pseudopodia and rhizopodia. Sometimes there are houses inlaid with iron or manganese salts. The vast majority have a dense cell membrane, solid or bicuspid. The cell wall is pectin, sometimes with cellulose and hemicellulose; in the genus Vaucheria it is cellulose. In many representatives, the shell is impregnated with silica or iron salts.

Features of the internal structure: One core, or many cores. Monad forms have 1-2 pulsating vacuoles. Motile and some coccoid forms have a stigma. Chloroplasts come in various shapes. They are surrounded by four membranes. Sometimes chloroplasts contain a pyrenoid. When lamellae form, thylakoids are grouped into groups of 3. Chloroplasts also contain a girdle thylakoid.

Pigments G-Z algae: chlorophylls “a” and “c”, carotenoids. Assimilation products are lipids, chrysolamine and volutin.

Reproduction: vegetative - by longitudinal cell division or disintegration of multicellular organisms into parts, asexual - by biflagellate zoospores, autospores, less often - amoeboids. In the genus Vaucheria, the spores are called synzoospores. The formation of endogenous cysts with a bicuspid membrane containing silica is also known. The sexual process is reliably known only in species of the genus Vaucheria, this is oogamy.

Distributed throughout the globe. They are found mainly in clean freshwater bodies of water, less often in brackish waters and seas. Many representatives are also common in soil. The relatively small division Xanthophyta is distinguished by a wide ecological amplitude.

Representatives: Tribonema, Vaucheria, Botrydium. Morphological and anatomical characteristics of the thallus, features of reproduction.

The most common representatives are:

Botrydium is a terrestrial alga that requires lime in the soil. In summer it can be found on damp soil near the shores of reservoirs, around puddles. It is visible to the naked eye in the form of green shiny bubbles 1-2 mm with a typically siphonal structure.

Vaucheria (Vaucheria) - thallus - sparsely branching threads without partitions, this is one giant multinucleated cell. It is found at the bottom of reservoirs with fast-flowing water, in stagnant reservoirs near the shore, and on heavily moist soil.

Representatives Xanthophyta

with monadic and amoeboid type of thallus structure

1 - Chlorocardion pleurochloron; 2 - Rhizochloris stigmatica:

A- periplast, b- rhizopodia, V- chloroplast, G- stigma, d- pulsating vacuoles.

3 - Stipitococcus vas; 4 – Myxochloris sphagnicola.

Representatives Xanthophyta with coccoid type of thallus structure

1 -2 – Botrydiopsis eriensis: 1 - an adult, 2 - formation of motor sports.

3 – Chlorothecium crassiapex;

4 – Peroniella curvipes.

Representatives Xanthophyta with a filamentous type of thallus structure

1 - Tribonema viride: A- part of the thread, b- exit of zoospores, G- shell structure. 2 - Heteropedia polychloris.

Lecture 4

Division of diatoms. Department of brown algae. Department of euglena algae

Division of diatoms –Bacillariophyta.

Diatoms are a completely special group of unicellular organisms (about 16,000 species), sharply different from other algae: their cells are surrounded on the outside by a hard silica shell - a shell. These are unicellular microscopic organisms, solitary or colonial in the form of chains, threads, asterisks, coccoid type of thallus structure. The sizes of individual specimens range from 4 microns to 2 mm. The cell membrane is a shell made of silica - silicon oxide with a thin layer of pectin substances. Pores, shell structure, epitheca, hypotheca, girdle ring, suture. The presence of a shell in diatoms predetermined interesting features of the structure of their cells, lifestyle and reproduction. The color of algae depends on a set of pigments, among which brown pigments predominate - carotene, xanthophyll and diatomine, which mask chlorophylls a and c in a living cell. Spare nutrients: oil, volutin, leukosin. Mechanism of movement of diatoms.

There are two evolutionary lines of diatoms, which differ primarily in the shape of the shell valves - centric (Centrophyceae) and pennate (Pennatophyceae). These are the two classes of this department.

Centric ones have radially symmetrical shell valves, most live in the water column, and their type of sexual process is oogamy. Class Centric - cells are single or connected in filamentous colonies. The valves are round in outline, the areoles are arranged randomly or radially, and along the edges of the valves there are outgrowths, spines, and setae. Mostly seaweed.

Pennates have no more than 2 planes of symmetry, sometimes only one plane of symmetry, many are mobile, the vast majority inhabit the bottom of reservoirs. Pennate diatoms produce amoeboid gametes, the type of sexual process is isogamy and anisogamy. Class Pennate - the shell is symmetrical along the longitudinal axis. The valves are linear, lanceolate, elliptic. These are freshwater and marine forms that live in benthos on various substrates.

1 – empty shell and living cellNeidium sp.; 2 – shell structure

centric diatoms; 3 – structure of the shell of pennate diatoms

d – hypovalva, p – girdle (po1 – epivalva girdle, po2 – hypovalvular girdle

valva, r – ribs, s – valve, e – epivalva, w – suture).

Cytoplasm, vacuoles, nucleus, chloroplasts. In most centric ones they are small and granular. In pennates, chloroplasts are usually large, lamellar, 1-2 per cell. Chloroplasts are surrounded by four membranes. Thylakoids in chloroplasts are grouped into lamellae of 3; there is a girdle thylakoid. The color of chloroplasts has various shades of yellow-brown. Diatom pigments: chlorophylls a and c, carotenoids. Nutrients accumulate in the cytoplasm in the form of lipid droplets and chrysolaminarin granules.

Reproduction. All diatoms are diploid, meiosis is gametic.

The hard shell determines the interesting characteristics of the reproduction of diatoms. The most common way is to divide the cell into 2 halves. Characteristics of the fission process and its consequences.

Restoration of the original cell size occurs as a result of the sexual process, leading to the formation of auxospores (growing spores). Presumably, the formation of auxospores is associated with cell shrinkage as a result of their division and the need to restore size. Auxospore formation is always associated with the sexual process. In pennate diatoms two cells come together, the valves move apart, reduction division of the nuclei occurs, after which the haploid nuclei of different cells merge in pairs and one or two aucospores are formed (the remaining haploid nuclei are reduced). In centric algae an aucospore is formed from one cell, in which the maternal diploid nucleus first divides into four haploid nuclei, two of them are reduced, and two merge, a zygote is formed, which, without a resting stage, sharply increases in size, forming an aucospore. After the aucospore matures, a new cell develops in it, in which an epitheca is first formed, then a hypotheca. All diatoms are diploid organisms.

The sexual process is isogamous, anisogamous and oogamous. The iso- and anisogamous process is carried out through gametes lacking flagella. In the oogamous process, the male gamete has a flagellum. This flagellum is unique in that it does not have central microtubules. Features of the sexual process of centric and pennate diatoms.

diagram of the sexual process

1-3 - in pennate diatoms,

4-5 – in centric diatoms

Possible ancestors of diatoms.

Type of nutrition: autotrophs and mixotrophs. Some are able to switch from autotrophic to heterotrophic nutrition. Very few forms have lost photosynthetic pigments and become heterotrophs.

Ecological features. Diatoms live everywhere: in various types of reservoirs, on soil, stones and rocks, in snow, on the surface and in small depressions, cracks, and ice. Sometimes under these conditions they develop in such masses that they turn it brown. Only mobile forms live in soil and outside water. The main habitat of diatoms is the aquatic environment. Diatoms are diversely represented in continental waters, as well as in sea waters. Most diatoms are cold-loving forms, so diatoms reach their most intensive development in spring and autumn. Diatoms serve as a constant food supply and the initial link in food purposes for many organisms. The nutritional value of planktonic diatoms is high, in particular the protein and fat content is higher than in potatoes and cereals. Some species serve as good indicators of seawater pollution by various wastewater and petroleum products; they are used in assessing the sanitary condition of coastal sea waters. Diatoms play a primary role in sedimentation - diatoms. The “diatomite” breed is known, which consists of 50-80% shells of diatoms. Due to their porosity and adsorption capacity, diatomites are used in the food, chemical and medical industries and in construction.

Systematics of diatoms. Class Centrophyceae - centric diatoms. Radially symmetrical shell valves, immobile. Most live in the water column. Their type of sexual process is oogamy. Chaetoceros, Cyclotella, Melosira

Class Pennatophyceae - pennate diatoms with bilaterally symmetrical shell valves, with and without a suture; forms with a suture are mobile. the vast majority inhabit the bottom of reservoirs. Pennate diatoms produce amoeboid gametes, the type of sexual process is isogamy and anisogamy. Pinnularia, Navicula.

The most common diatoms are:

Navicula, boat-shaped valves with sharp or tapered ends.

Pinnularia, valves are elongated-elliptical with a suture and clearly visible streaking.

Cymbella, the valves are sickle-shaped.

Navicula, pinnularia and cymbella are benthic algae and belong to the class Pennate. Of the centric planktonic species, you can find Cyclotella in our reservoirs, the single cells of which look like a low round box.

Department of brown algae -Phaeophyta.

The department of brown algae (about 1,500 species) includes numerous macroscopic algae, the common external feature of which is the yellowish-brown color of their thalli, due to the presence of yellow and brown pigments. Mostly disc-shaped chloroplasts contain chlorophylls a and c, carotenes and xanthophylls. The pyrenoids are very small. Spare nutrients - laminarin, mannitol (sugar alcohol), and in small quantities - fat. In addition to the usual organelles, the cells contain physodes, structures containing tannins. The cell membranes on the outside are mucilaginous - pectin, the inner layer is cellulose.

The type of structure of the thallus of brown algae is predominantly lamellar, often very complexly organized, and rarely multi-filamentous. The vast majority of representatives of this group are marine forms.

Thallus of brown algae range in size from several tens of micrometers to tens of meters (macrocystis - up to 50 m). In highly organized forms, the thalli are differentiated and resemble flowering plants. Some large representatives have air bubbles. All brown algae grow attached to soil or other algae. For attachment, they form rhizoids or a basal disk. In a cross section of large thalli of brown algae, zones are distinguished, occupied by cells of different structures, specialized to perform individual functions.

The cells are mononuclear, covered with thick membranes with large pores. The shell consists of an inner cellulose and outer layer, the basis of which is proteins combined with alginic acid and its salts. Algulose. Physodes. Chloroplasts are usually small, disc-shaped, less often ribbon-shaped and lamellar. A number of taxa have a pyrenoid in their chloroplasts. In chloroplasts, thylakoids are grouped into lamellae of 3. Pigments: chlorophyll a, c, carotenoids. Reserve nutrients in cells outside chloroplasts are laminarin (a polysaccharide) and mannitol (six-hydroxy alcohol), and lipids in small quantities.

Reproduction. At B.V. All main types of reproduction are found - vegetative, asexual and sexual. Vegetative propagation occurs when branches are accidentally separated from the thallus; these branches do not form organs of attachment and do not form organs of asexual and sexual reproduction. Reproductive organs are formed on them if their development has already begun by the time the thallus is detached from the ground. Asexual reproduction is carried out by zoospores (there are species that reproduce by mono- or tetraspores). The structure of zoospores. Pear-shaped zoospores have two unequal flagella on the side: the anterior one is long, the posterior one is short. The formation of zoospores and gametes in brown algae occurs in containers of two main types: single-locular and multilocular. Meiosis occurs when spores form in single-locular sporangia. The sexual process is isogamous, heterogamous and oogamous. All brown algae, with the exception of Fucus, have alternating generations; in the asexual generation (sporophyte) in zoosporangia (or tetrasporangia), after reduction division, zoospores (or tetraspores) are formed; from them grow haploid sexual plants (gametophytes), dioecious or bisexual. After fertilization, the zygote develops into a new asexual diploid plant (sporophyte) without a dormant period. In Fucus, the entire life of algae occurs in the diploid phase; only sperm and eggs are haploid, before the formation of which reduction division occurs.

Depending on the nature of the alternation of generations and the change of nuclear phases, brown algae are divided into 3 classes.

Class Isogenerate (Isogeneratae)

In most algae of this class, the sporophyte and gametophyte are the same in shape and size or do not differ very sharply in size. The sexual process is iso-, hetero- or oogamous. Representatives of the genus Ectocarpus are widespread in the seas; There are especially many of them in cold seas. They grow in the littoral and sublittoral zones. They participate in the fouling of ships and buoys. They look like small bushes or tufts, consisting of abundantly branching single-row filaments, often ending in colorless multicellular hairs. The growth of filaments is intercalary. Single-celled zoosporangia form on the sides of the branches. In them, reduction division and a number of divisions of the cell nucleus occur and the formation

many zoospores that emerge from the zoosporangium, after swimming for a short time, germinate into a plant of the same appearance, but haploid. On it, on short lateral branches, multicellular gametangia are formed, in which gametes that are identical in shape and size, but differ in behavior (+ and -) develop. The zygote, without a dormant period, grows into a new diploid thread with a zoosporangium. Ectocarpus is characterized by an isomorphic change of generations. The sexual process is isogamy.

Kutlariya (Cutleria) - distributed along the European shores of the Atlantic Ocean and the Mediterranean Sea. It has the appearance of dichotonically branched multilayered ribbons up to 20 cm in length, ending in hairs. Externally, cutleriaceae differ from other algae by the presence of a fringe of delicate hairs at the top or along the edge of the thallus. At the base of the hairs, on some specimens large-celled macrogametangia develop, producing biflagellate macrogametes; on other specimens, small-celled microgametangia develop, yielding microgametes. After fertilization, the zygote develops without a rest period into a new diploid plant - a sporophyte, which has the shape of a multilayer plate or crust, tightly pressed to the substrate. It is so unlike a gametophyte that it has been described under the new generic name Aglaozonia. On its upper side, unicellular zoosporangia develop, in which zoospores are formed after reduction division. Zoospores germinate into a ribbon-shaped bushy gametophyte. The genus Cutlaria is the most famous. She serves as an example of a heteromorphic change of generation; her sexual process is heterogamy.

Dictyota (Dictyota) grows mainly in tropical and subtropical seas, and is also found in the Black Sea. It is characterized by a forked-branched thallus with branches located in the same plane. The height of the plant is about 20 cm, the width of the branches is 4-8 mm. Dictyota has an isomorphic alternation of generations. On the sporophyte, large spherical tetrasporangia develop from the surface cells, in which, after reduction division, 4 haploid, immobile, naked tetraspores are formed. From tetraspores, male (with numerous antheridia, producing up to 30,000 sperm) and female (with oogonia, producing one egg) gametophytes develop. Mature eggs fall out of the oogonia. After fertilization, the zygote develops into a new sporophyte. Dictyota is an example of the development of algae with an isomorphic change of generations, in which the sexual process is oogamy.

Class Heterogeneous (Heterogeneratae)

In the development cycle of algae of this class, a macroscopic (in many powerfully developed) sporophyte and a microscopic small gametophyte alternate, which is often called a prothallus by analogy with ferns. The sexual process is isogamous or oogamous. Sporophytes of different genera differ sharply and are the largest lower plants, reaching a length of 60-100 m with significant morphological division and a complex anatomical structure. Sporophytes are divided into leaf blade, petiole and rhizoids or basal disc. At the junction of the plate and petiole there is an intercalary meristem. The sporophyte is perennial, with the exception of the plate, which dies off annually and is replaced by a new one. In the meristoderm of the plate, before its destruction, unicellular zoosporangia are formed. In each zoosporangium, after preliminary reduction division, from 16 to 64 (sometimes 128) zoospores are formed. Billions of zoospores are formed on one algae specimen. After a short period of movement, the zoospores germinate into microscopically small filamentous male and female gametophytes (prothallus). Antheridia produce one sperm, and oogonia produce one egg. After fertilization, a new powerful sporophyte gradually develops from the zygote.

So, heteromorphic alternation of generations is characteristic of heterogenate algae. The sexual process is oogamy.

Kelp (Laminaria) , species of the genus are widespread in the northern seas. The thallus is divided into leaf blade, trunk and rhizoids. It is found vertically from the sea surface to a depth of 200 m.

Longitudinal section of the petiole of a young kelp thallus

1 – at low magnification, 2 – at high magnification: a – tubular threads.

Macrocystis (Macrocystis) , growing at a depth of 10-20 m, has a multi-branched trunk up to 50-60 m long. In front of each plate, the branch is usually expanded into a pear-shaped air bubble. Thanks to air bubbles and long branches, the main part of the macrocystis thallus floats at the surface of the sea. It is mined throughout the world and processed into alginates and other chemical products.

Nereocystis (Nereocystis) It is represented by a long trunk (petiole) up to 15-25 m, which gradually expands upward, carries at the end a bubble with a diameter of 12-20 cm, from which narrow plates extend (up to 9 m).

There are 24-40 such plates in total. Nereocystis grows at depths of up to 20 m, while the upper part of the trunk with a bladder floats near the surface.

The life cycles of the above representatives are similar. Zoosporangia form on leaf blades.

Class Cyclosporae (Cyclosporeae)

This class includes brown algae, which do not have an alternation of generations, but only a change in nuclear phases: the entire algae is diploid, only the gametes are haploid. There is no asexual reproduction. The class contains only one order - Fucus.

Fucuses have leathery, olive- or yellow-brown, dichotonically branched, belt-like thalli 0.5-1 m long, 1-5 cm wide; some have swellings filled with air. Apical growth.

By the time of sexual reproduction, bean-shaped yellowish swellings are formed at the ends of the branches - receptacles, on which the genital organs are located. Gametophytes develop on the receptacles in the form of a layer lining the depressions (conceptacles or scaphidia). Gametangia form in depressions in a layer of cells that arises from a single cell called the conceptaculum initial cell or prospore. The lining layer of the conceptaculum developing from the prospore is the gametophyte. Fucus gametophytes form vertical branched and simple mononuclear multicellular filaments, some of them bear gametangia, and the rest serve as paraphyses.

Diploid life cycle of representatives of the genus Fucus

Oogonia in Fucus sit directly on the surface of the gametophyte. Antheridia are formed at the ends of branched branches. Developing oogonia (8 eggs) and antheridia (64 sperm) are excreted with mucus

they shoot out from the concentaculum, here the germ cells are released from them. Fertilization occurs in the surrounding water. The fertilized egg grows into a new plant without a dormant period.

Genus fucus (Fucus) distributed in the northern seas, it is the main inhabitant of the coastal zone.

Sargassum - “leaves” are lamellar or subulate. The trunk is short, long branches carrying receptacles extend from its upper part; these branches die off annually. Representatives are distributed mainly in tropical and subtropical seas. Sargassum is used to produce alginates; some species with non-rigid leaves are used as food. In the Sargasso Sea on an area of 4.4 million square meters. km swim two species of sargassum, which reproduce vegetatively and do not have organs of attachment.

Isomorphic or heteromorphic variants of the haploid-diploid life cycle or isomorphic and heteromorphic change of generations. Life cycles of the genera Ectocarpus, Laminaria, Fucus, Conceptacula, Receptacula or Scaphidia.

Distribution and ecology of B.V. Almost exclusively marine plants. They are distributed everywhere from the Arctic to the Antarctic. But the largest species grow mainly in temperate and subpolar latitudes. Representatives of the department grow mainly in shallow water and predominate on rocky coastal substrates in cold regions of the globe. but they are also found at depths of up to 200 m. Species that have air bubbles become free-floating when separated from the ground and sometimes (for example, in the Sargasso Sea) form large accumulations on the surface of the water. The most powerful thickets of B.V. form in waters rich in nutrients. Many large algae are widely used as livestock feed and to fertilize fields (rich in potassium). Some types of kelp are used as food; in addition to food, they also have dietary value, because rich in iodine and useful for atherosclerosis. Previously, iodine was extracted from kelp. Brown algae is used in significant quantities to produce algin, which has great adhesive ability and is used in the production of paper, cardboard, and printing inks. Algae is collected with special harvesting machines, and those thrown ashore are also used.

Department of euglena algae –Euglenophyta (about 1000 species)

E.V. - These are single-celled, mostly monadic organisms. Some representatives may have a coccoid and amoeboid form, and are also capable of transitioning to a palmelle state.

In most euglenoids, the cell is oval or spindle-shaped. Cell sizes vary from 4 µm to 0.5 mm. The cell wall of euglenoids is the pellicle. Metabolism, house - the genus Trachelomonas and Strombomonas.

Pharynx, reservoir, flagella, stigma, nucleus, chromosomes, chloroplasts. Chloroplasts are surrounded by three membranes. Thylakoids are grouped into lamellae of 3, rarely more. Some large chloroplasts have pyrenoids, which serve as the center for the formation of paramylon, a reserve nutrient. Most have paramylon in the form of granules outside the chloroplast. Forms without chloroplasts store lipids.

Pigments euglenoids: chlorophylls a and b, carotenoids. In addition to the autotrophic type of nutrition, a number of representatives are characterized by saprotrophic and holozoic types of nutrition. There are forms lacking chloroplasts. Many species change their feeding types in the light and in the dark.

Reproduction Euglenaceae: Sexual reproduction is not known with certainty. They reproduce by longitudinal cell division. Some euglenaceae transform into a palmelle state before reproducing. Some euglenaceae can form cysts under unfavorable conditions.

In the Euglena department, two evolutionary lines are visible, one of which gave rise to the other. The first, the initial one for the second, are heterotrophic representatives that do not initially possess chloroplasts. Through secondary endosymbiosis with green algae, they gave rise to a second lineage, the representatives of which contain chloroplasts with or without photosynthetic pigments. The evolution of the first line followed the path of increasing the diversity of types of absorption of organic substances from the outside and narrow specialization in this regard.

Ecology and distribution: Euglenaceae are inhabitants of fresh water bodies; a few forms live in sea waters. They prefer shallow, well-warmed reservoirs with standing water and an abundance of organic matter.

1 – Euglena viridis: a- tourniquet, b- pharynx, V- peephole, G- chloroplast, d- core;

2 –Euglena mutabilis;3 –Trachelomonas bituricensis;

4 –Strombomonas ensifera.

Lecture 5

Department of green algae –Chlor ophyta

This is the most extensive department of algae (about 20,000 species). All main types of morphological organization of the thallus, except amoeboid, are found in this section. These are unicellular, multicellular and noncellular organisms. Cells of most Z.V. have a cellulose and pectin shell, sometimes with the inclusion of sporopollenin, some with only a plasma membrane. Characteristics of flagella. Cells can be either mononucleated or multinucleated. Chloroplasts are varied in shape and have a clear green color. Tillakoids are grouped into very dense groups of 2 or more, forming grana. Many forms have a pyrenoid. Pigments - chlorophylls a and b, carotenoids. The reserve substance is starch and lipids.

At Z.V. There are all the main types of reproduction, types of sexual process and development cycles.

Most of the W.V. common in fresh water bodies, but there are species in salt water bodies and seas.

Green algae are considered as a line of development that led to the emergence of higher plants.

Division Z.V. in different systems it is different for classes. Actually green algae, class conjugates and class charophyte algae.

Among green algae, three groups are traditionally distinguished, which are assigned different ranks - classes or divisions. These are actually green algae, conjugates or cohesives and charophytes. The former are characterized by the presence in the life cycle of many species of a mobile stage, which has 2-4 identical smooth flagella. Conjugates are characterized by the absence of mobile stages and a special sexual process – conjugation. Characeae are characterized by a unique structure of the thallus, and the only exception among algae is the multicellular reproductive organs, which some researchers consider as a reduced gametophyte.

Class green algae – Chlorophyceae.

Occupies a central position among all green algae. In this class, the stages of morphological differentiation of the thallus are very fully represented, which are taken as the basis for dividing the class into orders. This is the largest class of Z.V-lei. The division into orders largely corresponds to the types of morphological structure of thalli.

Volvox order –Volvocales .

Includes Z.V. with a monadic organization of the thallus, i.e. equipped with flagella, unicellular, coenobial and colonial algae, mobile during vegetative life. Representatives – Chlamydomonas And Volvox, morphological characteristics, life cycle. Mostly freshwater organisms, they also live in the soil and melting snow in the highlands.

There are usually 2 flagella (1-3). The nucleus is spherical, in the center of the cell, there is one chloroplast, cup-shaped pariental with one large pyrenoid. In the anterior part of the ocelli, there are pulsating vacuoles. Most are autotrophs, heterotrophs and mixotrophs are known. Reproduction is vegetative, asexual and sexual (various forms). The zygote germinates after a period of dormancy.

Volvoxidae are typical active plankters. They live mainly in small, stagnant, often quickly drying up reservoirs. These are active cleaners of polluted and waste water. They are used in

as representative forms for the biological analysis of contaminated waters.

Among the representatives: dunaliella saline, which causes red “blooming” of water in water bodies oversaturated with salt, is a unicellular algae covered with a thin and delicate periplast (no cell wall). In the process of life, carotenoids accumulate in it, giving color. Its reproduction is mainly vegetative, through longitudinal cell division in a mobile state. The sexual process is hologamy.

Cell structure of Chlamydomonas sp.

Chlamydomonas proboscis has a dense double-contour shell, forming a protrusion in front - a spout. Inhabitant of well-warmed and heavily polluted water bodies. An active health worker in polluted waters, where it quickly multiplies and causes green “blooming” of both one species and several species of the genus. Asexual reproduction by zoospores. The sexual process is isogamy. Gametes are formed inside the mother cell in the same way as a zoospore, but in larger quantities (32-64) and correspondingly smaller in size.

Gonium is a coenobial form. 16 coenobium cells are located in one layer, surrounded by a general mucous membrane. Asexual reproduction is the formation of young coenobia in each cell. By the end of the growing season - isogamy.

Pandorina is a coenobium of 16 cells located compactly, touching their sides, and therefore acquire a multifaceted shape. Asexual reproduction is like in gonium, sexual reproduction is heterogamy.

Volvox - colonies in the form of balls with a diameter of up to 2 mm, in the peripheral layer from 20 to 50 thousand chlamydomonas-like cells, fused with side walls and connected to one another by plasmodesmata. Cell differentiation is observed within the colony. The vast majority are vegetative cells that do not take part in reproduction. Between them are larger reproductive cells. About a dozen of them are parthenogonidia, which, as a result of repeated divisions, give rise to young daughter colonies inside the mother colony. The sexual process is oogamy. Oogonia and antheridia also arise from reproductive cells.

Volvoxaceae are not a dead-end branch in the evolution of green algae. Having lost mobility, representatives of Volvoxaceae at some stage of evolutionary development passed the baton to protococcal algae.

In evolutionary terms, the transitional order from Volvocaceae to Chlorococcus is the order Tetarsporales, whose representatives have a coccoid, palmelloid type of thallus structure, but at the same time retain signs of a monadic organization - stigma, contractile vacuoles, flagella in some cases.

Life cycle Chlamydomonas

Scheme of asexual (1) and sexual reproduction (2)Volvoxaureus

Order chlorococcal, or outdated name protococcal -Chlorococcales - Protococcales .

Unicellular, colonial and coenobial coccoid forms are immobile in the vegetative state. The shell is cellulose or cellulose combined with sporopollenin. In terms of the structure of the protoplast, protococcals resemble volvoxaceae. The most primitive of them retained pulsating vacuoles, ocellus and even flagella, although the latter are immobile and are called pseudocilia. The presence of these vestigial organelles proves the origin of Protococcae from Volvoxaceae.

The vast majority are microscopic forms; in only a few genera the thallus can reach large sizes. The shape of the cells is varied, but spherical, elliptical and ovoid predominate. The cell wall is always solid, made of cellulose, less often with an admixture of pectin substances; in lower forms it is pectin. In many species, it is externally equipped with bristles, spines, spines, warts or mucus, which helps the cell float in the water column. The bulk of protococcal algae are planktonic forms. They are characterized by mixotrophy; some species are found in symbiosis with other organisms. Among the protococcal species there are endophytes that live in ciliates and lichens.

Vegetative propagation - cell division, fragmentation of a colony, or disintegration of coenobium into individual cells. Asexual reproduction by zoospores or autospores (aplanospores, autospores form coenobium in coenobial forms) Sexual reproduction is known in a few representatives, iso-, hetero-, oogamy.

The most primitive unicellular chlorococci are similar to chlamydomonas that have lost motility: spherical cells with a pectinocellulose shell, a cup-shaped chromatophore with one pyrenoid and a nucleus in the recess of the chromatophore, for example, chlorococcus, found in fresh water bodies and on damp soil. Chlorococcus reproduces by zoospores. The sexual process is isogamy. Similar in appearance to chlorococcus trebuxia, characterized by the shape of the chromatophore, which is not wall-shaped, cup-shaped, but massive, occupying the central part of the cell. Trebuxia lives on damp soil, in the lower part of tree trunks, on stumps, as an algal component that is part of most lichens.

Chlorella - spherical cells are covered with a smooth shell, contain a cup-shaped, or rather bell-shaped chromatophore. Chlorella reproduces exclusively by autospores, which appear 4 - 8 in one cell. Chlorella is undemanding to conditions and is widespread everywhere. In reservoirs it is a typical plankter. It is also found in benthos, on terrestrial substrates, and is part of lichens. Chlorella is good for

various studies, in terms of the number of works devoted to chlorella, it ranks first among algae. Well cultivated.

Scenodesmus- a genus characterized by coenobium, predominantly four-celled with rare spines on the membrane of the marginal cells. When multiplying in each cell of the colony, four autospores are formed, which form a young colony inside the shell of the mother cell.

Pediastrum characterized by microscopically small lamellar colonies of different multiples of two numbers of cells (from 4 to 128). The cells are multinucleated, usually arranged in concentric circles around a central one. The marginal cells bear wall outgrowths. Biflagellate zoospores are released through a gap in the wall of the mother cell and are surrounded by a mucous bladder. Gradually they are located in the same plane and form a small daughter colony. The sexual process is isogamy. The zygote experiences a period of rest.

"Water mesh" or hydrodiction common in quiet river backwaters, ponds, and pits. Its coenobia look like a mesh bag up to 1 m long. Each wall of the loop is a separate cell up to 1.5 cm long, formed from one zoospore.

Hydrodictyon reticulatum-water mesh

Inside each cell there is a complex chromatophore with many pyrenoids, and underneath there are numerous nuclei (up to several thousand). During asexual reproduction, the cell protoplast splits into 7,000-20,000 biflagellate zoospores. Zoospores do not leave the shell of the mother cell, move for a short time, fold into a new small mesh, which is released after the shell of the mother cell spreads, and gradually increases in size. The sexual process is isogamy. The zygote experiences a period of rest.

In the aquatic environment, predator kairomones influence the morphology, life cycle traits and behavior of the prey, including chlorococcal algae. The presence of Daphnia in water mainly caused the formation of Scenedesmus coenobia. Representatives – water mesh ( Hydrodiction), Chlorella, Scenedesmus, Pediastrum. Distributed in various types of almost exclusively fresh aquatic ecosystems, as well as in soil and on moist non-aquatic substrates.

Order ulothrix –Ulothrichales .

Ulothrix algae include algae that have a filamentous structure, as well as some lamellar and sac-like algae, which still have a filamentous shape at the beginning of ontogenesis. Filamentous algae, sexual process – isogamy, rarely oogamy. All plant cells can participate in plant growth, all can form spores and gametes, with the exception of the cells at the base of the filament with which they are attached. The cells of the body are autonomous: capable of regeneration, vegetative reproduction, and also capable of becoming reproductive.

During asexual reproduction, from 2 to 16(32) four-flagellate zoospores develop in all green cells. Typically this process begins at the apical (end cell) and progresses to the base of the filament. After a period of movement, the zoospore stops, shedding flagella one after another, attaches to the substrate and grows into a filament. During sexual reproduction, biflagellate gametes appear in cells

number 4(8)-32(64). The sexual process is often isogamous, heterothallism predominates. The four-flagellate zygote grows into a one-celled sporophyte (the sporophyte enters a dormant period), which, upon maturity, breaks up into 4-16 four-flagellate zoospores. Zoospores behave in the same way as zoospores of the asexual generation.

The representative is ulothrix girdled (Ulothrix zonata) , growing attached to the substrate in fast-flowing, clean streams. Ulothrix forms a thread of one row of cells dressed in thick

shell, the protoplast has a lamellar chromatophore that encircles the cell from the inside in the form of an open ring.

Representatives genus Ulva (Ulva) The thallus is two-layered, lamellar, reaches large sizes, has corrugated edges and is attached to the substrate with a base narrowed into a short petiole. Ulvacaceae, unlike ulothrixaceae, have a parenchymal structure and are predominantly marine inhabitants.

Enteromorpha (Enteromorpha) has two layers of plate cells, which in the early stages of development are separated and the thalli take the form of an intestine or tube with a single-layer wall. Hence its Russian name -

nie - intestines. Enteromorpha lives in both marine and fresh water bodies.

Most ulothrixaceae have a thallus in the form of a single-row unbranched thread. Less commonly, the thallus is lamellar or tubular. Characteristics of morphology, life cycle Ulohtrix, Ulva. Marine and freshwater forms.

Order Chaetophoraceae –Chaetophorales .

Includes algae with a heterotrichous or heterotrichous type of structure. The formation of unicellular or multicellular hairs is characteristic. Vegetative propagation by fragmentation of the thallus, the formation of akinetes. Asexual - zoospores. Isogamy, heterogamy and oogamy. Mainly inhabitants of fresh waters. Main representatives - Stigeoclonium, Draparnaldia, Coleochaete. Most chaetophorans have so-called hairs or

bristles. In some, these are the terminal cells of the branches, highly elongated and devoid of content. For others, these are outgrowths of the shell. Chaetophorans are predominantly freshwater organisms; most of them have a thin layer of mucus covering their body. U chaetophores all threads are immersed in a dense mucous membrane, which has a spherical or leaf-shaped shape. The basal part of the chaetophore consists of individual spherical cells, from which vertical filaments diverge radially, densely branched at the apex. An interesting algae belongs to the same family friciella (Fritschiella) , the only species that has adapted to exist in the soil. Creeping filaments extend under the soil surface, from which rhizoids extend downwards, and vertical filaments extend upwards. The latter, reaching the soil surface, branch densely, forming bunches of branches.

1 –Stigeoclonium tenue;2 –Draparnaldia glomerata;3 –Coleochaete scutata;4 –Fritschiella tuberosa;5 –Chaetophora elegans.

The tendency to reduce the vertical system has led to the formation of a large number of creeping forms. All creeping representatives of the family are, as a rule, epiphytes or endophytes. This is a widespread algae trantepoly (Trentepohlia), its accumulations form powdery orange or brown aggregations on stones, stumps, tree trunks, and wooden buildings. Its color is due to the presence of hematochrome in the cells. This algae grows especially abundantly in humid tropical climates. Many types of trentepoly are an algal component of lichens - with adaptation to a terrestrial lifestyle: vegetative and asexual reproduction; in asexual reproduction, sporangia are formed on stalks, which are carried by the wind. The reproduction of algae of the order Chaetophoraceae resembles the reproduction of Ulothrixaceae: four-flagellated zoospores, isogamy, and in marine forms - an isomorphic change of generations.

Order Oedogonium -Oedogoniales .

Filamentous algae with a peculiar cell division, during which caps are formed. characteristics of the process of vegetative cell division. Zoospores and spermatozoa are multiflagellate – stephanokontous. They differ from ordinary monadic cells in that at the anterior end they bear many flagella arranged in a circle. The bases and roots of the flagella are tightly connected by a fibrous ring. The sexual process is oogamy. Widely distributed in fresh water bodies. Representative – Oedogonium.

OrderCladophorales– Cladophoraceae.

The type of thallus structure is siphonocladal. Typically, the filaments are attached to the substrate by rhizoids and intertwine to form mud. Vegetative propagation, fragmentation of thalli, akinetes. Asexual - zoospores. Sexual reproduction – isogamy, heterogamy. Cladophoraceae are common in both seas and freshwater bodies. Representative – Cladophora.

The order Bryopsidae, or Siphonaceae, and the order Dasycladaceae -Bryopsidales - Siphonales , Dasicladales

Siphonal type of thallus structure. Although the thallus consists of a single cell, its external shape can be very complex. ( transparent) The thallus has a dense cell membrane, inside there is a large vacuole and wall cytoplasm. The protoplast of bryopsids is multinucleate. In Dasycladaceae, the thallus is a huge mononuclear radially symmetrical cell of complex morphology. Chloroplasts are numerous, disc-shaped or sometimes one reticulate, formed by the connection of small chloroplasts with each other. Vegetative propagation – by fragmentation of thalli. Asexual – with stephanokont zoospores in Brypsididae, absent in Dasycladaceae. The sexual process is isogamy and anisogamy. The vast majority are marine organisms, distributed mainly in the tropics.

Bryopsidaceae – Caulerpa, Codium, dazyclad - Acetabularia.

Order siphonocladaceous –Siphonocladales .

Siphonocladal type of thallus organization. Marine life. Representative - clan Valonia.

Class conjugates – Conjugatophycea or Zygnematophyceae.

The class includes unicellular and filamentous algae, common in fresh or slightly brackish water bodies. There are also terrestrial species. The type of thallus structure is coccoid, filamentous. They live unattached in fresh water bodies, less often in damp places in the ground. The class includes about 4,500 species. Their features are the complete absence of flagellar stages (zoospores and gametes equipped with flagella) and a special type of sexual process in the form of conjugation. The formation of zygotes in conjugates is a rather rare phenomenon. All haplobionts are in a vegetative state. In most cases, unicellular conjugates reproduce by ordinary vegetative division in the transverse plane, and filamentous conjugates reproduce by disintegration of filaments into individual cells. The cells of the conjugate are mononuclear, the chromatophores are large, ribbon-shaped.

A feature of the class is the absence of asexual reproduction and flagellar stages. Vegetative propagation by cell division and fragmentation of thalli. They also form akinetes. A peculiar sexual process is conjugation. Meiosis occurs during germination of a zygospore (zygotic meiosis).

Order Mesothenic –Mesotaeniales .

The order includes single-celled forms surrounded by mucus. The shell is whole. The chromatophore in cells is central lamellar, stellate or wall-shaped in the form of spiral ribbons. Reproduction by transverse cell division. The zygote forms a thick shell and after a period of rest and meiosis forms 2 or 4 cells.

Representatives – Mesotaenium, Spirotaenia, Netrium.

They are common in peat bogs and on damp soil, wet rocks, some develop inside the snow in the highlands.

Order Zygnema -Zygnematales .

Filamentous, non-branching algae, covered with a mucous sheath. The cell membrane is solid and without pores. Chloroplasts are of 3 types. They reproduce mainly vegetatively from parts of the thallus. Conjugation is scalariform or lateral. The zygote grows into one seedling. Representatives of the genus Spirogyra exhibit a gliding movement in the direction of greatest illumination. It occurs only between the threads and does not require contact with a solid substrate.

Representatives: Mougeotia(masculinity), Zygnema, Spirogyra.

Spirogyra (Spirogyra) - the most extensive genus among the Zygnemaceae (about 340 species) - has spirally twisted green chloroplast ribbons (from 1 to 16). Spirogyra has numerous pyrenoids along the midline of the chloroplasts. The nucleus is large with a clearly visible nucleolus. In Spirogyra, the resting state of vegetative cells used for reproduction is known - aplanospores, akinetes, which are formed from vegetative cells by reducing their contents and development

secondary shell.

Muzhotsia (Mougeotia) characterized by a chloroplast in the form of a wide axial plate. The chloroplast is mobile. In bright light it rotates 90 degrees on its axis and appears narrow green

a strip running down the middle of the cell.

Zignema (Zygnema), it can be easily recognized by its two large star-shaped chloroplasts. In the center of the cell, between the chloroplasts lies the nucleus.

Order desmidiaceae –Desmidiales .

This is a vast order, including several thousand species. These are unicellular forms. The peculiarity of algae is that the cells consist of two symmetrical parts. The cell wall also consists of two halves and, unlike cells. The walls of algae of the 2 previous orders are penetrated by large pores, which are sometimes complexly arranged. Algae are capable of movement due to the directed secretion of mucus through the terminal pores. Chromatophores are often axial single, or each half of the cell has its own chromatophore.

They reproduce through cell division in a plane of symmetry. When a zygote germinates, 2 seedlings are usually formed. Vegetative reproduction: first, the nucleus lying in the isthmus region divides mitotically, the nuclei diverge to the centers of both semicells. After the nuclei have moved into half-cells, a septum is formed in the middle. Two old half-cells are separated from one another. In each new cell, 1/2 of the shell is older than the other.

The sexual process in these algae is quite rare. In the zygote, during the resting period, the gamete nuclei lie side by side. Their fusion occurs before germination. At the same time, the protoplast is divided into two parts. As a result, one of the nuclei in each newly formed protoplast dies, and the other increases in size: two seedlings are formed. Subsequently, a constriction is formed in the middle of each seedling. The two seedlings usually have different sex signs.

Desmidiaceae are found in small low-flowing reservoirs, swamps, and rivers among fouling. They prefer soft waters with low pH. Most of them are benthic organisms. Cosmopolitan, but in certain geographical areas they are endemic. Unique organizational features, shell features, peculiarities of vegetative division and sexual reproduction indicate the need for an ecological approach to the habitats of desmidian algae.

Examples of unicellular organisms: Cosmarium, Micrasterias.

Representatives:

Closterium (Closterium) - the cells are single, crescent-shaped, without constrictions, the nucleus is located in the cytoplasmic bridge, and there is a chromatophore in each crescent horn.

Penium (Penium) - rod-shaped cells, with rounded ends, without constrictions, semi-cells are almost isodiametric.

Cosmarium - round cells, with a constriction in the middle.

Desmidium - short triangular cells without constrictions connected into threads.

1 2 3 4 5 6 7

Mesotaeniales: 1 - Spirotaenia erithrocephala; 2 - Netrium digitus; Zygnematales: 3 – Mougeotia; 4 – Zygnema; 5 – Spirogyra; Desmiiales: 6 - Cosmarium subtumidum; 7 – Micrasterias conferta.

Class chara algae - Charophycea.

1-3 - Upper part of thalli: 1 –Nitella mucronata,2 –Tolypella prolifera;3 –Chara vulgaris.

Characeae are the most highly organized algae, having both a complex type of thallus structure and sexual reproductive organs. The class has about 300 species. They are distributed mainly in freshwater bodies of water. They prefer reservoirs rich in calcium salts, where they form thickets of thalli usually several decimeters high, and sometimes more than a meter. Attachment to the substrate using rhizoids. Outwardly, they often resemble higher plants, especially horsetails. Morphology and anatomy of the thallus. The type of thallus structure is charophytic. The articular-whorled structure is expressed in the fact that on the main shoots, at some distance from each other, there are whorls of short, equal-sized lateral shoots, also of an articulated structure. The location of the whorls is nodes. Each internode is one multinucleate segmented cell up to several cm long. The outside of the internode is covered with a layer of special cells - the cortex.

Characeae cells have a dense cell wall made of cellulose, often containing calcium carbonate. Inside the cell contains a large vacuole. The cytoplasm is wall-like with numerous chloroplasts. Rapid movement of the cytoplasm is observed in cells. The speed of cytoplasm movement reaches 1.5 - 2 mm per minute.

Charovars are characterized by the absence of asexual reproduction. Vegetative propagation occurs due to the formation of nodules on the lower stem nodes and on rhizoids at the tips of the thallus. The sexual process is oogamy. The greatest originality is in the structure of the reproductive organs. The female organ is the oogonium, the male organ is the antheridium. Oogonia are oval, up to 1 mm long, consisting of an egg and its outer cover of five narrow cells. At the bottom, the oogonia is equipped with a single-celled stalk, and at the top with a crown of five or ten short cells. Antheridia are spherical, up to 0.5 mm in diameter, formed by eight flat cells, fastened at the edges, with processes extending inward. These cells, called scutes, form the outer wall of the antheridium. On the internal processes of the antheridium, antherozoids mature - long, spiral-shaped with two flagella at the anterior end. One antheridium contains 40,000 antherozoids. Antheridia are initially green, but mature brick red. Oospores develop inside oogonia as a result of fertilization of the egg. Mature oospores are brownish-yellow, their outer wall is impregnated with suberin and silica. There are reserve substances inside: grains of starch and drops of fat. After a period of dormancy and reduction division, one seedling emerges from the oospore (three nuclei degenerate), and a normal shoot develops from the seedling. All charophyte algae plants are haploid. Vegetatively, charophyte algae reproduce either by nodules formed on rhizoids and on the lower stem nodes, or by rooting branches from the lower nodes. There is no asexual reproduction by special spores.

The most common genera in the reservoirs of our zone are:

Nitella (Nitella). It is distinguished by branched “leaves”; the branching segments are usually unicellular. The genital organs are located on the branching nodes of the “leaf”, above it is the antheridium, and below it is one or more oogonia. There is no bark on the “stems”.

Hara (Chara). “Leaves” with “stipules”, well-developed single-layer and multi-layer “bark”. The genital organs are usually found in pairs. Common stinking chara (Chara foetida) is a thin-stemmed, rigid plant with long “leaves” - and hara brittle (Chara fragillis), characterized by non-branching “leaves”.

Lecture 6

General characteristics of mushrooms

A large group of organisms, including about 100,000 species. They occupy a special position in the system of the organic world; fungi differ significantly from plants in their inability to photosynthesize and, accordingly, in their heterotrophic mode of nutrition; they were united on the basis of such similarities as a well-defined cell wall, adsorption of nutrients from solutions, and lack of mobility for the most part in the vegetative state . However, the heterotrophic method of nutrition leaves its mark on the nature of metabolism in fungi. Based on such characteristics as the presence of urea in the metabolism, formation as

the storage product of glycogen, not starch, and the content of chitin in the cell wall, fungi are similar to animals.

Most fungi are decomposers, i.e. By destroying organic matter, they act as intermediaries between the living and inert matter of the biosphere, thus completing various biochemical cycles. The 70-100 thousand species of mushrooms known from publications, according to experts, constitute only a twentieth of their true number. Like algae, fungi are an artificial ecological-trophic group, which includes heterotrophic eukaryotes with an osmotrophic type of nutrition. Previously, mushrooms were classified as lower plants. Currently, they are classified as an independent kingdom of living organisms. The commonality of nutritional types does not mean the common origin of mushrooms. This group includes a large number of evolutionary lines that arose independently or diverged very long ago. Some of these lineages are called mushroom-like protists. The uniqueness of mushrooms is determined by the fact that they combine a number of characteristics of both plants and animals. Fungi are similar to plants due to immobility of vegetative stages, unlimited apical growth, the presence of cell walls, nutrition by absorption of nutrients, and the ability to synthesize vitamins. They are similar to animals in the absence of chlorophyll and a heterotrophic type of nutrition, the presence of chitin (a polymer of N-acetyl-D-glucosamine) in the cell walls, the formation of urea (H 2 NCONH 2), the storage of carbohydrates in the form of glycogen, the structure of cytochromes (electron carrier proteins in redox reactions).The uniqueness of fungi lies in the peculiarities of their life cycles (change of nuclear phases, the presence of dikaryons, heterokaryosis, parasexual process).

Fungi are heterotrophs; they obtain nutrition through extracellular breakdown of the substrate due to the activity of enzymes released into the external environment and subsequent absorption of soluble breakdown products. The vegetative body of most mushrooms is represented by mycelium or mycelium, which consists of hyphae.

Fungi can exist in three life forms - mycelial (most taxa), yeast-like and plasmodial. In many species, the first two life forms can, under certain conditions, transform into one another. Types of mycelium - nonseptate and septate. Some unicellular fungi with nonseptate mycelium have the following type of structure: from one or several parts with nuclei they develop branched, nuclear-free thread-like structures called rhizomycelium. In mushroom-like protists, the vegetative body can usually be represented by amoeboid cells, plasmodia and pseudoplasmodia.

Cell walls are more than 80% composed of polysaccharides, which form a complex complex with proteins, lipids, polyphosphates, pigments (melanin) and other compounds. The most common carbohydrates are: glucans - polymers of glucose, chitin, chitosan, and sometimes mannans - polymers of mannose. In representatives of different sections of fungi, the composition of the cell wall varies. The membrane of fungal cells is multilayered. The inner layer covering the plasmalemma consists of chitin molecules. Next comes a layer of glycoprotein molecules, the outer layers are formed by glucans. Most mushrooms have a reserve nutrient - glycogen.

In fungi, differentiation of hyphae and individual sections of mycelium can be observed. As a result of adaptation to perform certain functions, hyphae and parts of the mycelium change their appearance. Stolons, anastomoses, trapping hyphae, appressoria, haustoria, mycorrhiza, ectotrophic and endotrophic mycorrhiza, arbuscules. Hyphal plexuses: loose, delicate cobwebby plexus of mycelium, films, cords or cords, rhizomorphs. Sclerotia.

Mycorrhiza, appressorium, haustorium

The hyphae grow apically, branch profusely and, with their interlacing, form false tissues in many fungi, which are often differentiated according to their functions and structural features into integumentary, internal, conductive and mechanical. Sclerotia, rhizomorphs, and fruiting bodies consist of false tissues.

Mushroom propagation.

Vegetative propagation is most often carried out by separating parts of the mycelium. In unicellular fungi of the yeast type, cell budding is common. The formation of chlamydospores can be considered as a special method of vegetative propagation. Asexual reproduction is carried out using spores. Spores can form endogenously inside sporogenous organs (sporangia) or exogenously on special outgrowths of the mycelium (conidiophores). In many lower fungi, asexual reproduction occurs with the help of zoospores. Zoospores develop in zoosporangia, have flagella and are capable of movement in water. Zoospore flagella have an internal structure characteristic of most eukaryotes. On the outside, the flagella are smooth or feathery due to two rows of mastigonemes. The number of flagella is usually 1-2. Fruiting bodies, micromycetes, macromycetes.

Sexual reproduction. Gametogamy, gametangiogamy, somatogamy, hologamy. Dikaryotic mycelium, parasexual process. Anamorph, teleomorph, pleiomorphism.

Mushroom sporulation organs

1-3 – microscopic:1 , 2 – conidiophores with conidia,3 – zoosporangium; 4-8 – macroscopic

Lecture 7

Myxomycetes, slime molds –Myxomycota

Oomikota Department –Oomycota

Division Chytridiomycota – Chytridiomycota

Division Zygomycota –Zygomycota

For historical, didactic and practical reasons, some living organisms are united by the concept “mushrooms”. We will look at the largest departments. In this case, forms with mobile stages (slime molds and lower fungi), together with algae and protozoa, belong to the kingdom of “protists” or “protoctists”. It is currently believed that divisions of fungi-like protists arose and developed independently of each other and each of them could be considered an independent kingdom. Higher mushrooms, i.e. organisms whose spores are immotile (Zygomycota, Ascomycota, Basidiomycota, Deutheromycota) constitute one evolutionary line and form the tsatsvo “Fungi” - real mushrooms, mushrooms in the narrow sense of the word. Their origin is assumed to be from Chytridiomycota.

Myxomycetes, slime molds –Myxomycota(more than 800 species)

Plasmodium, pseudoplasmodium. Some slime molds are characterized by the presence of large amounts of lime. Most slime molds contain pigments in their plasmodium that give them different colors. The bulk of slime molds are saprophytes that live inside and on the surface of damp, decaying wood and other organic substrates, as well as in the soil. Osmotrophy, phagotrophy of plasmodium. body. Plasmodium actively moves towards food sources, wetter places and towards the flow of water.

Department of oomycota –Oomycota (about 800-1000 species)

Order Saprolegniaceae – Saprolegniales.

The life of saprolegnia fungi takes place in an aquatic environment. Of these, most belong to freshwater species, but there are also sea inhabitants. ( transparent).

Saprolegnia.

Representatives of the genus Aphanomyces develop in the soil, causing a disease called “root beetle”, because The fungus develops mainly in the area of the root collar.

Drinking order – Pythiales

Characteristics of morphology, lifestyle and life cycle Phytophthora infestans. Order Peronosporaceae – Peronosporales.

Unlike other peronosporans, sporangiophores Albugocandida develop under the plant cuticle. The mycelium of this fungus is located in the intercellular spaces of the plant and from it haustoria protrude into the cells, absorbing nutrients. Chains of rounded cells develop on sporangiophores. When they develop in large numbers, the cuticle breaks and these cells are carried away by the wind. In the presence of dripping liquid water, they germinate with zoospores, which infect new plants.

Division of chytrid fungi -Chytridiomycota .

Asexual reproduction by monoflagellate spores. In this case, in some fungi the entire body turns into sporangia (such forms are called holocarpic), in others only part of the body becomes zoosporangium (these forms are called eucarpic). Eucarpic fungi are capable of forming several sporangia at once. The sexual process is iso, hetero- and oogamy, as well as somatogamy. Meiosis is zygotic. Relationship between diploid and haploid phases.

Characteristics of morphology, lifestyle, life cycle Olpidium brassicae, Synchytrium endobioticum, Chytridium.

Department of zygomycota -Zygomycota (870 species)

This is the first group of fungi that does not have motile stages. Fungi of this division have a well-developed multinucleate noncellular mycelium, which in some fungi in a mature state can become cellular. Cell walls contain chitin and chitosan. The reserve substance is glycogen. Asexual reproduction is carried out by sporangiospores, which form in sporangia, or by conidia, which form on conidiophores.

The sexual process of zygomycetes is zygogamy, which consists of the fusion of the contents of cells undifferentiated into gametes. Meiosis is zygotic. The ratio of diploid and haploid phases.

Order Entomophthoraceae - Entomophthorales(over 150 species)

Order Zoopaguidae - Zoopagales

Order Glomicae – Glomales

They form mycorrhizae with herbaceous plants; the formation of arbuscules is characteristic.

LECTURE 8

Ascomikot Division –Ascomycota

This is one of the largest departments of mushrooms - over 32,000 species. It is believed that most of the ascomycota are not discovered and the total number of species may be 10-20 times greater. A characteristic feature of this group is the formation of ascospores after the sexual process, which are enclosed in bags or asci. In most ascomycetes, the ascus contains eight ascospores and actively releases spores.

In the simplest case, the body of ascomycetes is represented by single budding cells. Most have septate mycelium. Septa, Voronin bodies, transport of substances and organelles. In many species, hyphae can be closely intertwined (especially during the formation of fruiting bodies) and form false tissues.

A - hyphal wall,b - septa,V - it's time; arrows indicate Voronin bodies

The cell walls contain chitin and glucans. Chitin makes up a smaller proportion of cell wall polysaccharides (20-25%), and in yeast it is present only in trace amounts or is absent altogether. The basis of the yeast cell wall is glucans and mannans (mannose polymers). The reserve nutrient is glycogen.

There are no moving stages in the development cycle. Asexual reproduction of ascomycetes is carried out by conidia. Coremia, sporodochia, bed, pycnida.

During the sexual process, bags are formed. The sexual process of ascomycetes is gametangiogamy, sometimes somatogamy. Antheridium, ascogon, trichogyne, plasmogamy, ascogenous hyphae, process of bursa formation, spore release mechanisms, ascocarp or ascoma. Haploid, dikaryotic, diploid stages of the development cycle.

Sexual reproduction of higher ascomycota

1 – antheridium, ascogon and trichogyne; 2 – development of bursae and ascospores; 3 – bursae with 8 spores.

The Ascomycota department is divided into 5 classes.

Class Archeascomycetes -Archiascomycetes

This group was isolated as a result of phylogenetic DNA analysis. This is the most ancient line of development of Ascomycota. This is a very diverse group in morphology and lifestyle. It includes representatives with yeast-like and mycelial organization of the vegetative body. This includes an interesting representative that causes pneumonia (pneumonia) in people with reduced immunity ( Pneumocystis). Fruiting bodies are not formed.

Fruiting bodies are not formed; bags develop directly on the mycelium. Many do not have true mycelium; they are represented by single cells that reproduce by budding or division.

Order Saccharomycetales(obsolete name - Endomycetales)

Throughout all or most of its life cycle, yeast exists as individual cells. “Yeast” is a physiological and morphological category. Yeast fungi are present not only in Ascomycota, but also in Basidiomycota. It is assumed that yeasts are secondary simplified forms of fungi, a life form adapted to exist in a liquid environment. Budding, pseudomycelium, sexual process. Representatives - Saccharomyces cerevisiae, Candida albicans.

Class Plectomycetes –Plectomycetes

Asci are formed in cleistothecia. These are predominantly soil saprotrophs. Many cause degradation of complex biopolymers, such as starch and cellulose, and some are capable of destroying keratin.

Order Eurociaceae –Eurotiales .

This group contains representatives whose anamorphs are described as members of the genera Aspergillus, Penicillium. Most of them are saprotrophs, living in the soil on plant debris. Some develop on food products and various industrial materials. The main type of reproduction for many Eurociaceae is the formation of conidia. In some, sexual reproduction has not been detected and only conidial stages are known; such fungi are classified in the department of imperfect fungi - Deutheromycota.

Class Hymenascomycetes -Hymenoasco mycetes .

The bursae are formed in the hymenium or hymenial layer in the ascocarp or ascoma. The formation of ascocarps occurs after plasmogamy. In this case, haploid hyphae entwine the developing ascogenous hyphae and bags, forming the integumentary tissue of the fruiting body. Cleistothecia, perithecia, apothecia. Morphology, method of spore release.

Order powdery mildew mushrooms –Erysiphales .

Orderhypocraeous –Hypocreales .

Characteristics of the lifestyle, life cycle of ergot purpurea ( Claviceps purpurea) and representatives of the genus Cordyceps.

Orders Leotiaceae and Peciaceae -Leotiales AndPezizales .

Sclerotinia sclerotiorum, violet dog – Peziza violacea, conical morel – Morchella conica, morel hat - Verpa bohemica, ordinary lines - Gyromitra esculenta. French truffle – Tuber melanosporum. Truffle lifestyle. Stereothecia.

TOclass ascolocular or loculoascomycetes (Loculoascomyces )

The bags develop inside plexuses of hyphae (ascostromes), which are formed before the sexual process occurs. Representative – causative agent of apple scab Venturia inaequalis.

LECTURE 9

Division Basidiomycota –Basidiomycota (more than 30,000 species) .

Basidiomycota are characterized by well-developed multicellular mycelium. There are no mobile stages; the cell membrane is formed by glucans and chitin. Distinguish primary And secondary mycelium(dikaryotic). Dolipore septa. The type of sexual process is somatogamy. The ratio of haploid and diploid phases. The process of formation of basidia, buckles, sterigma, basidiospores. Asexual reproduction, i.e. The formation of conidia in basidiomycetes is rare. More often, fruiting bodies or basidiomas are formed that have a hymenial layer. Paraphyses, cystids. Types of basidia: holobasidia, phragmo- or heterobasidia.

CLASS CHOLOBASIDIOMYCETES –HOLOBASIDIOMYCES .

The class combines fungi with unicellular basidia. Basidia can form directly on the mycelium, be collected in the hymenial layer on the surface of the fruiting bodies, or develop inside the fruiting bodies.

GROUP OF ORDER HYMENOMYCETES

This is almost half of all known basidiomycetes. Basidia develop on fruiting bodies in the hymenial layer. Fruiting bodies can have a wide variety of shapes: in some they are represented by crusts spread over the substrate with a hymenium on the upper side. In others, the fruiting bodies may be coral-shaped, hoof-shaped, funnel-shaped, in the form of a cap on a stalk, etc. The hymenophore is smooth, serrated, lamellar or tubular.

Within the group of orders of Hymenomycetes, the evolution of the types of fruiting bodies and methods of placing the hymenophore on them can be traced. The most primitive can be considered flat crust-shaped fruiting bodies with a hymenophore on the upper surface, then there are fruiting bodies with a developed three-dimensional structure and a smooth hymenophore covering its entire surface, and finally, the most progressive are fruiting bodies in which the hymenophore is raised above the substrate, located below the cap and it is protected by it, has outgrowths and ensures maximum production of basidiospores.

Aphyllophoroid Hymenomycetes

Agaricoid Hymenomycetes

GROUP OF ORDER GASTEROMYCETES.

Now some mycologists distinguish this group of approximately 1,100 species of fungi and 14 orders into a separate class Gasteromycetes. The main feature of gasteromycetes is that their fruiting bodies are closed until the spores are fully mature. The hymenial layer is located inside and is almost always destroyed by the time the basidiospores mature. The release of spores from the fruiting body occurs after the spores are separated from the basidia. Gasterocarp, peridium, gleba. Most are soil saprotrophs, some form mycorrhizae with tree species. Some species live on dead wood. In forests, these species take part in the decomposition of dead wood.

According to their characteristics (color, structure, methods of reproduction, etc.), algae are divided into several types (divisions): green, blue-green, golden, diatoms, yellow-green, pyrrophytic, euglenic, red and brown algae.

Let's give a brief description of the types.

Green algae - Chlorophyta

Unicellular, colonial, multicellular and noncellular forms. Multicellular forms are represented mainly by filamentous algae. Some are distinguished by a complex internal structure, reminiscent of higher plants in appearance.

Algae are purely green in color, however, in addition to green chlorophyll, the chromatophores contain yellow pigments - carotene and xanthophyll. The cell membrane consists of fiber. Chromatophores with pyrenoids.

Reproduction is carried out by vegetative, asexual and sexual means. Vegetative propagation occurs by dividing the organism into parts. Asexual reproduction is carried out by motile zoospores with flagella of equal size (usually 2-4 of them) or aplaiospores - immobile spores.

With the help of zoospores, green algae not only reproduce, but also disperse. The sexual process of reproduction is varied. Representatives of green algae are Chlamydomonas, Spirogyra, Chlorella, Ulothrpx, Cladophora, Closterium, etc.

Blue-green algae - Cyanophyta

Unicellular, colonial and filamentous forms. Algae have blue-green, yellow-green, olive green and other types of colors. The color is explained by the presence of four pigments in blue-green algae: green chlorophyll, blue phycocyan, red phycoerythryp-pa and yellow carotene. These algae do not have a formed chromatophore and nucleus, flagellar stages and the sexual process are absent. Blue-green algae include: oscillatoria, nostoc, gleotrichia, anabena, etc.

Golden algae - Chrysophyta

Single-celled and colonial forms. They contain chlorophyll and phycochrysipus, which is why the color of representatives of this group of algae is golden or brownish-yellow. The cells are in some cases naked or covered with a poorly differentiated protoplasmic membrane; golden algae are found, the body of which is dressed in a shell or enclosed in a house.

Some forms are mobile and move with the help of flagella, while other forms are immobile in a vegetative state. They reproduce by division or zoospores.

Capable of forming cysts to withstand unfavorable conditions. The sexual process is very rare. Representatives of this type of algae are mallomonas, dinobrion, chrysameba, etc.

Diatoms - Bacillariophyta

Unicellular and colonial organisms with a silicified shell consisting of two halves called valves. Chromatophore I<ел-того или светло-бурого цвета от наличия в нем, кроме хлорофилла, бурого пигмента диатомина. Размножение осуществляется путем деления клеток на две, у некоторых диатомовых наблюдается образование двужгутиковых зооспор. Известен половой процесс. К диатомовым водорослям относятся пинну л я р ия, навикула, плевросигма, гомфонема, сиредра, мелозира и др.

Yellow-green, or heteroflagellate, algae - Xanthophyta, or Heterocontae

These include unicellular, colonial, filamentous and noncellular forms. These algae contain, in addition to chlorophyll, yellow pigments - xanthophyll and carotene; their color varies from light to dark yellow-green. Reproduction occurs by longitudinal cell division, zoospores (they are characterized by the presence of two flagella of unequal size and unequal structure), and autospores. The sexual process is known. Representative: botridium.

Pyrrophyte algae - Pyrrophyta

Unicellular and colonial forms. In addition to chlorophyll, algae contain the pigment pyrrophyll, which gives the algae a brown and brownish-yellow color. The cells are naked or covered with armored membranes. They reproduce by division, zoosiors, autosiors. They form cysts. Sexual reproduction is rare. Pyrrophyte algae include: peridinium, ceracium, etc.

Euglenophyta - Euglenophyta

Unicellular motile forms with one or two flagella, sometimes without them; the cells are bare, the role of the shell is played by the outer layer of protoplasm, sometimes the cell is located in the house. Most algae are green in color, sometimes light green due to the presence of xaptophylla. Reproduction occurs by longitudinal division, the sexual process is unknown. Representatives of euglena algae are euglena and facus.

Red algae, or purple algae, Rhodophyta

They live mainly in the seas, only a few live in fresh waters. These are multicellular algae, colored red.

(with different shades). The color of algae is associated with the presence in them, in addition to chlorophyll, of other pigments - phycoerythrin and phycocyan.

Asexual reproduction is carried out by aplano-spores. The sexual process is very complex and is characterized by the presence of male organs - antheridia and female organs - oogonia, or carpogones.

The representative is batrachospermum.

Brown algae, Phaeophyta

The name was given due to the yellow-brown color of the thallus, caused by the presence, in addition to green chlorophylls, of a large number of brown carotenoid pigments. Multicellular, predominantly macroscopic algae (the largest organism living in water is the brown algae macrocystis, which reaches a length of 60 m, growing by 45 cm per day).

Reproduction is vegetative, asexual and sexual. Gametes and zoospores bear two flagella on the side, different in length and morphology. Brown algae are widespread in all seas of the planet; they often form underwater forests, reaching their greatest development in the seas of temperate and subpolar latitudes, where they are the main source of organic matter in the coastal zone. In tropical latitudes, the largest accumulation of brown algae is in the Sargasso Sea. Representatives of only a few genera live in desalinated and fresh waters, for example, Pleurocladia, Streblonema, Lithoderma.