Panels
Yellow green algae are examples. Department of yellow-green algae – Xanthophyta

Yellow green algae are examples. Department of yellow-green algae – Xanthophyta

Department of yellow-green or heteroflagellate algae

These algae are characterized by the following pigments: chlorophylls a, c, e(chlorophyll b absent), P-carotene, e-carotene, xanthophylls: antheraxanthin, lutein, zeaxanthin, neoxanthin, violaxanthin, voucheriaxanthin, heteroxanthin, diadinoxanthin, diatoxanthin. The cell usually contains two lamellar chromatophores, which lie in the endoplasmic reticulum tank, which is in direct connection with the nuclear membrane; trithylakoid lamellae are located in the chloroplast matrix; almost always (xanthophyceae) there is a girdle lamella (absent in eustigmatophyceae); the internal pyrenoids of xanthophyceae contain trithylakoid lamellae. The eye (stigma) is part of the plastid (xanthophyceae) or the stigma granules are located outside the plastid (eustigmatophyceae).

Reserve products: volutin, fat, often chrysolamine; starch is not formed. The longer flagellum bears mastigonemes, the shorter flagellum is smooth. Cell membranes often consist of two or more parts; cysts (statospores), like those of golden algae, are endoplasmic, their membranes are fossilized.

In Fig. Figure 22 shows diagrams of monad cells of yellow-green algae.

In most modern systems, two classes are distinguished: xanthophyceae and eustigmatophyceae.

This class includes algae at various stages of differentiation of the thallus: monadic, rhizopodial, lalmeloid, coccoid, filamentous, siphonous. In accordance with the types of organization of the thallus, orders are distinguished that are parallel to the orders of golden, dinophyte, and green algae. The order Heterochloridales unites monadic forms, the order Rhizochioridales includes rhizopodials, the order Helerogloeales - palmelloids, the order Mischococcales - coccoid, the order Tribonematales - filamentous, the order Bo(rydiales) - siphonous seaweed.

The last three orders are discussed below.

Order mischococcal -Mischococcales

The order includes numerous unicellular and colonial coccoid forms. Cells of various shapes are covered with a cell wall, often consisting of two parts. Reproduction by zoospores or aplanospores.

Genus botridiopsis(Botrydiop. sis) widespread in freshwater bodies of water (ponds, ditches, etc.), represented by single spherical cells, covered with a cell membrane, under which there is a wall cytoplasm containing numerous disc-shaped chloroplasts, and in mature cells - many cell nuclei. The center of the cell is occupied by a large vacuole with cell sap, intersected by thin strands of cytoplasm. Drops of oil and clumps of chrysolaminarin are scattered in the cytoplasm. Reproduction by zoospores and autospores, which are formed in large quantities in the cell (up to 300). U IN.arrhiza during zoospore formation, as in many other yellow-green algae (Characiopsis, Tribonema, Bothridium, etc.), along with typical zoospores, synzoospores are often observed (see also Chapter 4).

Tribonemal order -Tribonematales

Unites filamentous forms. Widely distributed in fresh waters can be considered as a representative genus tribonema(Tribonema). The thallus is represented by an unbranched filament composed of one row of cells.

Cylindrical, often slightly barrel-shaped cells, usually mononuclear, mostly contain several chloroplasts. In the cytoplasm there is fat, chrysolamine. The cell wall always consists of two halves, with their edges facing each other in the median plane of the cells. Each half of the shell is made up of a number of overlapping layers.

Even before the division of the cell nucleus (at the interphase stage), a new cylindrical piece of the membrane is laid in the equatorial region under the old cell membrane - an intermediate ring. At a later stage of mother cell division, during cytokinesis, a transverse septum is formed in the middle of this hollow cylinder. The new shell, which has an H-shape in its longitudinal optical section, when growing, pushes both older halves of the mother cell wall apart from each other, inserting itself between them. In this way, the membranes of neighboring cells are connected to each other; accordingly, each cell is surrounded by two halves of adjacent H-shaped figures. When reproductive cells are released or under the influence of certain agents (for example, strong chromic acid), the cell membrane disintegrates into H-shaped sections. Fragments of threads always end in empty halves of H-shaped figures, which in profile look like two points. Reproduction of filaments, continuously growing due to transverse cell divisions, is carried out vegetatively - by fragmentation and asexually - through zoospores, amoeboid cells, aplanospores, akinetes.

Order botridial-Botrydiales

Unites xanthophycean algae, which have a siphon organization.

Representatives botrydium genus{ Botrydium) live on damp land. The thallus is siphonic, differentiated into an aerial part in the form of a spherical pear-shaped bladder with a diameter of 1-2 mm, and a rhizoidal part immersed in the substrate, usually branched. This normal form of the thallus can vary noticeably depending on external conditions. For example, when botrydium is cultivated immersed in water, thalli in the form of branched threads are observed. The wall is multilayered, with cellulose microfibrils differently oriented in each layer. The cytoplasm is concentrated in the wall layer and surrounds a continuous vacuole with cell sap. In the adult thallus, the cytoplasm contains numerous nuclei; in the aerial part, there are abundant disc-shaped chloroplasts with pyrenoids and other organelles. Reproduction is carried out by mononuclear zoospores with two heterokont and heteromorphic flagella, which arise when the bladder is immersed in water (after rain, etc.). Synzoospores were also observed. Then settling along the edge of the puddle, on the drying soil, the zoospores develop into new plants. In drier weather, aplanospores are formed instead of zoospores. Upon reaching a certain internal maturity, botridium enters the dormant stage. Russian researcher V.V. Miller, who studied the genus Botridium in detail in culture, described various methods for the formation of resting cysts. In some cases, the entire contents of the bladder give rise to one large cyst with a thick shell. V.V. Miller called such cysts “macrocysts” (IN.walirothi, IN.tuberosum, IN.pachidermum). In other cases, the contents of the aerial part divide to form many multinucleate sporocysts (IN.walirothi). Finally, all or part of the contents of the bladder can pass into rhizoids and form rhizocysts there. The latter are either arranged in many rows, for example, in IN.granulatum, or the contents pass into the swollen ends of the rhizoids, in each of which a cyst is formed, for example in IN.tuberosum. The same species may have different forms of cysts, which, under different external conditions, replace each other. All forms of cysts do not require a period of rest for their germination; they can germinate immediately after their appearance. Small cysts (rhizocysts, sporocysts arranged in a row) either directly germinate into new individuals or form zoospores. Large cysts (macrocysts, rhizocysts formed singly IN.tuberosum) They usually germinate by zoospores or aplanospores. V.V. Miller did not observe the sexual process in any of the studied species of botridium. However, there is data from other authors about the existence of IN.granulatum sexual process, iso- and heterogamous in different races. These data need confirmation

PAGE_BREAK--

U sort of voucheria(Vaucheria) (both freshwater and marine and saltwater species are known) thallus in the form of branched siphon threads, forming cotton-like accumulations in the water or extensive dark green tufts on moist soil. The growth of filaments is apical. In the vegetative filaments of the voucheria, starting from the apex, three zones can be distinguished: apical, subapical and vacuolated. The apical segment is an actively growing part of the siphon thallus: there are numerous vesicles and mitochondria; chloroplasts and cell nuclei are absent. The vesicles contain fibrous material, possibly a precursor of the cell wall material (cellulose). In the subapical zone, the number of vesicles decreases, chloroplasts and cell nuclei appear. The chloroplasts are numerous, disc-shaped, and lack pyrenoids. The bud-shaped pyrenoid is observed only in Woucheria seedlings. Associated with each cell nucleus is a pair of centrioles, which during prophase of mitosis migrate to opposite poles of the elongating nuclei. The nuclear envelope remains intact during mitosis, an intranuclear spindle is formed inside it, and there are no centromeres; between diverging chromosomes, the nuclear envelope is laced and surrounds the telephase daughter nuclei. Normal mitosis occurring inside the shell of the maternal nucleus was observed by L. I. Kursanov (1911) in a number of Voucheria species. In all studied species, L.I. Kursanov noted an interesting distribution of nuclear divisions along the thread: having begun in one place, mitoses little by little spread to neighboring areas, etc. Thus, on a preparation that records a certain moment of this process, we get what can best be called a wave of divisions, where individual division phases, successive in time, along the thread are located in the correct sequence. In the apical and subapical zones there is still no central vacuole. Only in the older - vacuolated - part of the thread does a vacuole with cell sap appear (Fig. 23, A). Reproduction is asexual, through synzoospores and aplanospores.

The formation of synzoospores, their release, sedimentation and germination were traced in Vaucheriafontinalis at the electron microscopic level (Fig. 23.5 "- E). When a synzoospore is formed at the somewhat swollen end of the filament, the central vacuole disappears, and all the organelles accumulate here. Pairs of centrioles associated with cell nuclei form internal flagella. Cell nuclei and internal flagella are grouped around emerging vesicles into which the flagella protrude. The bubbles migrate to the surface of the protoplast and merge with the plasmalemma. Thus, the flagella reach the surface of the future synzoospore.

Synzoospores of voucheria are covered with numerous smooth pairs of flagella, very slightly varying in length. A septum appears, separating the sporangium with the synzoospore from the vegetative thread. The release of the synzoospore apparently occurs after enzymatic dissolution of the apex of the zoosporangium. The recently arrested synzoospore is spherical, large, the central vacuole is absent, the flagella are retracted, initially maintaining the typical (9 - 9 + 2) axoneme configuration; their membranes become part of the plasmalemma. the nuclei occupy the subsurface zone. At first there is no cell wall, but in the peripheral layer of the cytoplasm there are abundant vesicles with fibrillar material, which apparently contain cellulose precursors. Their disappearance coincides with the deposition of a thin wall on the surface of the synzoospore. The nuclei are displaced, and chloroplasts and other organelles invade the peripheral area. The axonemes of the retracted flagella are destroyed, and the centrioles take their usual position next to the cell nuclei. A large central vacuole is formed. A bulge appears at one or both ends of the encysted zoospore, in which vesicles with fibrillar material, mitochondria, dictyosomes, chloroplasts, and nuclei accumulate, as is observed at the tip of the vegetative filament. The central vacuole of the encysted zoospore begins to lengthen (Fig. 23, G- L),

The sexual process is oogamous. Freshwater species of Washeria are mostly monoecious, while marine species are dioecious.

The genital organs appear in the form of lateral outgrowths of a filament containing numerous nuclei: more or less spherical in shape in the case of oogonia and in the form of a cylindrical tube twisted like a horn in the development of the antheridium. Both types of sexual outgrowths first communicate with the vegetative thread on which they are formed, and are later separated from it by a transverse wall. In the case of oogonia, before the formation of the transverse septum, all nuclei, except one, which becomes the nucleus of a single egg, migrate with very mobile cytoplasm back into the vegetative thread. According to other data, excess nuclei degenerate after separation of the oogonia from the filament by a transverse septum. In the antheridium, which is separated by a transverse septum from the tip of the male outgrowth, numerous nuclei are preserved and a large number of sperm arise. The spermatozoon of the vaucheria without chloroplast and stigma, with large mitochondria, is equipped with two heterokont flagella, the anterior flagellum with mastigonemes being shorter than the smooth posterior one. In the anterior part of the sperm there is a protrusion with microtubular skeletal elements, reminiscent of the so-called proboscis of the fucus sperm. The genital organs open, sperm penetrate the oogonia and fertilize the egg, which, after fertilization, secretes a thick membrane. The copulation nucleus in the oospore germinating after a period of dormancy is reducedly divided.

Some researchers, attaching great importance to the differences in the structure of the flagellar apparatus in spermatozoa and synzoosiora vaucheria, even separated this genus into the department Vaucheriophyta, placing the remaining yellow-green algae as a class Heteroconlae in the department Chrysophyta. Other authors combined the genera Bothridium and Vaucheria into the division Siphonophyta, later demoting this taxon to the rank of class Xanthosiphonophyceae along with Xanthophyceae within the division Chrysophyta. Segregation of the genus Waucheria from other yellow-green algae at such a high level apparently did not meet with the support of many researchers. However, the separation of Vaucheria into a separate order Vaucheriales is accepted by many authors.

Class eustigmatophyceae (Eustigmatophyceae)

This class was isolated from the xanthophyceae based on the structure of the monadic cells (zoospores), primarily their ocelli. The ocellus is a large orange-red body at the extreme anterior end of the zoospore, independent of a single plastid, and consists of an irregular group of droplets with no limiting membranes and no membrane around the entire complex. Thus, unlike xanthophyceae, the stigma here is located outside the plastid. Another distinctive feature of evetigmatophyceae is that the thickening of the flagellum, overlying the stigma, is located at the proximal end, directed anteriorly and bearing two rows of flagellum hairs. A smooth, backward-directed flagellum is usually absent. In addition, in eustigmatophyceans, the trithylakoid lamellae often form grana-like stacks, the peripheral girdle lamella is absent, the pyrenoid, found only in vegetative cells (absent in zoospores), protrudes from the inner surface of the plastid and is not crossed by thylakoids.

All eustigmatophyceae are unicellular coccoid forms (formerly classified as mischococcal from the class xanthophyceae).

These algae are characterized by the following pigments: chlorophylls a, c, e (chlorophyll b is absent), P-carotene, e-carotene, xanthophylls: antheraxanthin, lutein, zeaxanthin, neoxanthin, violaxanthin, voucheriaxanthin, heteroxanthin, diadinoxanthin, diatoxanthin. The cell usually contains two lamellar chromatophores, which lie in the endoplasmic reticulum tank, which is in direct connection with the nuclear membrane; trithylakoid lamellae are located in the chloroplast matrix; almost always (xanthophyceae) there is a girdle lamella (absent in eustigmatophyceae); the internal pyrenoids of xanthophyceae contain trithylakoid lamellae. The eye (stigma) is part of the plastid (xanthophyceae) or the stigma granules are located outside the plastid (eustigmatophyceae).

In Fig. Figure 22 shows diagrams of monad cells of yellow-green algae.

In most modern systems, two classes are distinguished: xanthophyceae and eustigmatophyceae.

The last three orders are discussed below.

Order Mischococcales

The order includes numerous unicellular and colonial coccoid forms. Cells of various shapes are covered with a cell wall, often consisting of two parts. Reproduction by zoospores or aplanospores.

The genus Botrydiopsis (Botrydiop.sis) is widespread in freshwater bodies of water (ponds, ditches, etc.), represented by single spherical cells, covered with a cell membrane, under which there is a wall cytoplasm containing numerous disc-shaped chloroplasts, and in mature cells - many cell nuclei. The center of the cell is occupied by a large vacuole with cell sap, intersected by thin strands of cytoplasm. Drops of oil and clumps of chrysolaminarin are scattered in the cytoplasm. Reproduction by zoospores and autospores, which are formed in large quantities in the cell (up to 300). In B. arrhiza, during zoonospore formation, as in many other yellow-green algae (Characiopsis, Tribonema, Bothridium, etc.), along with typical zoospores, synzoospores are often observed (see also Chapter 4).

Order Tribonemales-Tribonematales

Unites filamentous forms. The genus Tribonema, widespread in fresh waters, can be considered as a representative. The thallus is represented by an unbranched filament composed of one row of cells.

Order botridial-Botrydiales

Unites xanthophycean algae, which have a siphon organization.

Representatives of the genus Botrydium live on damp soil. The thallus is siphonic, differentiated into an aerial part in the form of a spherical pear-shaped bladder with a diameter of 1-2 mm, and a rhizoidal part immersed in the substrate, usually branched. This normal form of the thallus can vary noticeably depending on external conditions. For example, when botrydium is cultivated immersed in water, thalli in the form of branched threads are observed. The wall is multilayered, with cellulose microfibrils differently oriented in each layer. The cytoplasm is concentrated in the wall layer and surrounds a continuous vacuole with cell sap. In the adult thallus, the cytoplasm contains numerous nuclei; in the aerial part, there are abundant disc-shaped chloroplasts with pyrenoids and other organelles. Reproduction is carried out by mononuclear zoospores with two heterokont and heteromorphic flagella, which arise when the bladder is immersed in water (after rain, etc.). Synzoospores were also observed. Then settling along the edge of the puddle, on the drying soil, the zoospores develop into new plants. In drier weather, aplanospores are formed instead of zoospores. Upon reaching a certain internal maturity, botridium enters the dormant stage. Russian researcher V.V. Miller, who studied the genus Botridium in detail in culture, described various methods for the formation of resting cysts. In some cases, the entire contents of the bladder give rise to one large cyst with a thick shell. V.V. Miller called such cysts “macrocysts” (B. walirothi, B. tuberosum, B. pachidermum). In other cases, the contents of the aerial part are divided to form many multinucleated sporocysts (B. walirothi). Finally, all or part of the contents of the bladder can pass into rhizoids and form rhizocysts there. The latter are either arranged in many rows, for example, in B. granulatum, or the contents pass into the swollen ends of rhizoids, in each of which a cyst is formed, for example in B. tuberosum. The same species may have different forms of cysts, which, under different external conditions, replace each other. All forms of cysts do not require a period of rest for their germination; they can germinate immediately after their appearance. Small cysts (rhizocysts, sporocysts arranged in a row) either directly germinate into new individuals or form zoospores. Large cysts (macrocysts, formed individually by rhizocysts of B. tuberosum) usually germinate with zoospores or aplanospores. In none of the studied species of Botridium B. V. Miller did not observe the sexual process. However, there is data from other authors about the existence of a sexual process in B. granulatum, which is iso- and heterogamous in different races. These data need confirmation

In the genus Vaucheria (both freshwater and marine and saltwater species are known), the thallus is in the form of branched siphon threads, forming cotton-like accumulations in the water or extensive dark green tufts on moist soil. The growth of filaments is apical. In the vegetative filaments of the voucheria, starting from the apex, three zones can be distinguished: apical, subapical and vacuolated. The apical segment is an actively growing part of the siphon thallus: there are numerous vesicles and mitochondria; chloroplasts and cell nuclei are absent. The vesicles contain fibrous material, possibly a precursor of the cell wall material (cellulose). In the subapical zone, the number of vesicles decreases, chloroplasts and cell nuclei appear. The chloroplasts are numerous, disc-shaped, and lack pyrenoids. The bud-shaped pyrenoid is observed only in Woucheria seedlings. Associated with each cell nucleus is a pair of centrioles, which during prophase of mitosis migrate to opposite poles of the elongating nuclei. The nuclear envelope remains intact during mitosis, an intranuclear spindle is formed inside it, and there are no centromeres; between diverging chromosomes, the nuclear envelope is laced and surrounds the telephase daughter nuclei. Normal mitosis occurring inside the shell of the maternal nucleus was observed by L. I. Kursanov (1911) in a number of Voucheria species. In all studied species, L.I. Kursanov noted an interesting distribution of nuclear divisions along the thread: having begun in one place, mitoses little by little spread to neighboring areas, etc. Thus, on a preparation that records a certain moment of this process, we get what can best be called a wave of divisions, where individual division phases, successive in time, along the thread are located in the correct sequence. In the apical and subapical zones there is still no central vacuole. Only in the older - vacuolated - part of the thread does a vacuole with cell sap appear (Fig. 23, A). Reproduction is asexual, through synzoospores and aplanospores.

The formation of synzoospores, their release, sedimentation and germination were traced in Vaucheria fontinalis at the electron microscopic level (Fig. 23.5 "-E). When a synzoospore is formed at the somewhat swollen end of the filament, the central vacuole disappears, and all organelles accumulate here. Associated with cell nuclei, pairs of centrioles form internal flagella. Cell nuclei and internal flagella are grouped around the emerging vesicles, into which the flagella protrude. The vesicles migrate to the surface of the protoplast and merge with the plasmalemma. Thus, the flagella reach the surface of the future synzoospore.

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

The term algae covers a large group of organisms belonging to lower plants that contain chlorophyll and have a primitive body structure, not divided into stems, leaves and roots, like higher plants. Due to the presence of chlorophyll, a green pigment, they are colored green. But in some cases, this color is distorted by the presence of additional pigments in the cells, such as; phycocyan (blue), phycoerythria (red), carotene (orange), xanthophyll (yellow), etc. Depending on the amount of certain pigments, algae have different colors. [...]

Yellow-green algae are characterized by great morphological diversity.[...]

Yellow-green algae are mainly representatives of plankton, mainly passive plankters; they are less common in periphyton 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.[...]

Several types of spores can be found in algae. Many of the green and yellow-green chlorococci have spores that cover themselves with a membrane inside the mother cell. Such spores are called aplanospores. When a particularly thickened shell is formed, they are called hypnospores, since they are capable of remaining dormant for a long period of time. Hypnospores are formed one at a time per cell, but, unlike akinetes, the mother cell membrane does not participate in the formation of their shell. Sometimes aplanospores immediately in the mother cell acquire a shape similar to it. In such cases they talk about auto disputes.[...]

Vegetative cells in such a thallus are of two types: internal, irregularly polygonal in outline, and marginal, somewhat larger and rounded. Each heteropedia cell contains several disc-shaped chloroplasts (this is reflected in the species name). Reproduction is carried out by biflagellate zoospores, which are formed mainly from midline cells. In addition, autospores can also form. Heteropedia is found mainly in moist soil.[...]

Of the algae, the object of research was a marine monoculture from the algae collection created at the Institute of South Sea Biology - a representative of the yellow-green algae (Nephrochloris salina). Rotifers (Brachionus plicatilis plicatilis) were used for toxicological studies.[...]

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).[...]

Red algae also develop abundantly in the upper horizons of the sea, including in the littoral zone. Here they are exposed to strong lighting, and at low tide - to direct solar radiation. In conditions of strong lighting, the color of the purple flowers changes greatly. Brown, yellow, and green tones appear in their color. This is due to changes in the composition of pigments and an increase in the role of chlorophyll. Color change depending on light is a reversible process. Even dry specimens that had lain for some time in the herbarium acquired a more intense color in the absence of light. In the tropics, where insolation is so strong that it is sometimes destructive, many scarlet plants are no longer able to grow in the littoral zone and descend to the sublittoral zone.[...]

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.[...]

Type III. Blue-green algae (Cyanophyceae) include unicellular, colonial and filamentous forms. A distinctive feature of these algae is a peculiar blue-green color, due to the presence of four pigments in their cells: green, blue, red and yellow. Depending on the quantitative ratios of pigments, the color of algae also changes.[...]

Diatoms as a division are not directly related to other divisions of algae. Some individual characteristics, such as the commonality of pigments, the similarity of assimilation products, the presence of a silica shell and resting spores, reveal a distant relationship with the divisions of golden algae (Crybolya) and yellow-green algae. Some algologists even now unite them as classes in the general department Chryvoryla. [...]

Golden algae are a very ancient group of algae that arose from some primary amoeboid organisms. In terms of the set of pigments, the composition of reserve substances and the presence of silicon in the membranes of vegetative cells and cysts, golden algae show similarities with diatoms, yellow-green and partly brown algae. There is reason to believe that it was golden algae that at one time gave rise to diatoms.[...]

Of the soil algae, the most sensitive to oil pollution are yellow-green and diatoms, less so are blue-green algae, especially nitrogen fixers. Oil pollution of soils leads to a sharp reduction in the species composition and number of algae in general and the active part of algal flora in particular. The sterilizing effect of oils on algae is especially pronounced at a depth of 10 - 20 cm. The toxicity of oil and its penetration deep into the soil depends on the type of economic use of the soil and is less pronounced in a meadow than in arable land; with increasing humidity, toxicity decreases.[...]

Yellow-green algae reproduce by simple cell division or the disintegration of colonies and multicellular thalli into separate parts. 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).[...]

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 often develop in spring and autumn, although there are species found throughout all periods of the year, including winter.[...]

In the second group of algae, along with chlorophyll a, there is a second chlorophyll, but different from that of green algae, chlorophyll c. There are also carotenoids, including specific ones that are not found in green ones. Carotenoids in the pigment complex of algae of these groups are involved in photosynthesis, thanks to them their color is golden, yellow, brown and brownish-green. Starch in these plants is replaced by other carbohydrates. These include the following departments: golden algae, diatoms, brown algae (Fig. 5).[...]

Therefore, in relation to such algae, it is customary to talk about cyclomorphosis. It can cover several generations or be limited to the period of growth and development of one individual. [...]

In some cases (in green, woolly, brown, and some yellow-green algae) the stigma is located in the chloroplast (Fig. 11, 1, 2), and in others (in euglena, oribatid flagellates) - outside it, in the immediate vicinity from the motor apparatus of the cell (Fig. 11, 3, 4, 5).[...]

They are close to the pigments of blue-green algae, but are not identical to them, as they differ in chemical composition. As has been shown in numerous experiments, the number of pigments in scarlet mushrooms increases with depth; in this case, the amount of phycoerythrin increases to a greater extent than the amount of chlorophyll. Anyone who has collected these algae in nature knows that red-colored algae grow at depth and that in shallow water they change color. As the amount of light increases, they become pale red, then yellow-green, straw-colored, and finally completely discolored.[...]

This class includes yellow-green algae with a siphonal structure, i.e., a non-cellular structure of the thallus. Xanthosiphonova may have a complex shape in appearance, but according to the structure of the protoplast, they all represent one giant multinucleated cell, most often of macroscopic size, visible to the naked eye. As a rule, the xanthosiphon thallus is terrestrial, attached, differentiated into a colored aboveground and colorless underground part. [...]

The distribution pattern of algae changes when moving from one soil-vegetation zone to another. In areas with sparse vegetation cover, algae occupy the free surface of the soil, where they grow quickly and intensively during periods of temporary moisture and favorable temperature. In the Arctic desert and tundra, such films are formed by green, yellow-green and blue-green algae. In the thickness of tundra soils, algae (mainly single-celled green) develop only in the uppermost layers.[...]

Two species from the department of yellow-green algae belonging to the order Heterococcales were discovered: Ellipsoidion solitäre, Pleurochloris magna.[...]

In the vast majority of algae, the shells are solid, although, as in yellow-green, desmidia and diatoms, there are also composite shells made up of two or more parts. [...]

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 calling 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.[...]

For the germination of algae spores and zygotes, a set of conditions is required, including certain values of temperature, light, and the content of nutrients and biologically active substances. Otherwise they will not germinate. At the same time, the zygotes of some algae, for example fucus, which do not belong to hypnozygotes, remain viable for three to four months. The reproduction and preservation of some algae in unfavorable conditions is facilitated by the formation of cysts. They are known from golden, yellow-green, diatoms and dinophyte algae. One cyst is formed in each cell. The cell contents become rounded and a hard shell containing silica is developed around it. When cysts germinate, one individual is formed, rarely several.[...]

The presence of plasmodial forms in yellow-green algae to a certain extent confirms the family ties of this department with golden algae, since only in these two departments there are representatives with a similar body structure (cf. Myxochrysis paradoxa from the department Chrysophyta).[...]

Visual changes in filamentous algae in a toxic environment can be expressed in a change in their color (chlorosis) with a gradual transition from green to yellow, brown, brown or complete discoloration (albinization). A decrease in cell turgor and the rupture of connections between them under the influence of a toxicant is externally expressed in the softening of filamentous algae, a decrease in their resistance to rupture, homogenization of the plant mass and its transformation into an amorphous pulp. If a substance tends to inhibit (inhibit) the photosynthesis of algae, then oxygen bubbles disappear in the test culture (especially when exposed to bright sunlight), and a lump of algae settles to the bottom. This is clearly visible against the background of the control experiment, in which the algae float up, lifted by bubbles of released oxygen. Substances that stimulate photosynthesis cause the formation of a large number of bubbles (merging into large bubbles) and the floating of a lump of algae. Excess oxygen and corresponding alkalization of the medium lead to chlorosis and destruction of the test culture. Stimulants can also cause rapid growth of the crop and its intensive greening. The final stage of destruction of the test culture is its lysis (the organic mass disappears, and the water turns yellow, brown or brown with secreted pigments). Lysis accelerates when the temperature rises to 25° C and above. [...]

This type includes yellow-green algae, similar in structure to green algae, but without starch.[...]

Less noticeable in the forest are the growths of algae among mosses - on their leaves and stems.[...]

The color of chloroplasts in diatoms has different shades of yellow-brown color depending on the set of pigments, among which brown pigments predominate - carotene, xanthophyll and diatomine, which mask chlorophylls a and c in a living cell. After the cell dies, the brown pigments dissolve in water and the green chlorophyll becomes clearly visible.[...]

The xanthococcal class includes yellow-green algae with a coccoid body structure. Their cells have a real dense shell, consisting of two parts, or a solid one, often sculptured or inlaid. These are unicellular, less often colonial forms, and the latter have the appearance of clusters of cells that are not immersed in mucus and are weakly connected to each other. During vegetative propagation, such colonies do not form threads and plates. Among the xanthococcals there are both free-floating and attached forms.[...]

The total number of algae species found in the soil is already approaching 2000. About 1,400 species, varieties and forms have been found in the soils of the USSR to date, relating mainly to blue-green (438), green (473), yellow-green (146) and diatoms (324) algae (Fig. 39).[...]

In July 2003, the total number of soil algae species in the study area decreased. We identified 19 species: among them there are approximately equal numbers of green and blue-green - 8 (42%) and 9 (48%) and one species each of diatoms (5%) and yellow-green (5%).[...]

The xanthomonad class includes representatives of yellow-green algae with a monad body structure. Their characteristic feature is the presence of two unequal bundles, allowing them to move in the water column. Like the xanthopods, the xanthomonas include a small number of mostly monotypic genera.[...]

The monad structure is very widespread in the world of algae - it is characteristic of many representatives in the divisions of pyrophytic, golden, yellow-green, yellow-green and green algae, and in the first three it is predominant. [...]

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. 188.2 - 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.[...]

Under forest vegetation in podzolic and gray forest soils, algae develop mainly in the upper layer of soil, as well as in litter. Algal groups of forest soils are uniform throughout the entire zone. They are dominated by green and yellow-green algae, the number of which reaches 30-85 thousand cells per 1 g, and the biomass does not exceed 20 kg/ha. [...]

The most numerous group consists of endosymbioses of unicellular green and yellow-green algae with unicellular animals (Fig. 48, 1). These algae are called zoochlorella and zooxanthellae, respectively. Among multicellular animals, green and yellow-green algae form endosymbioses with freshwater sponges, hydra, etc. (Fig. 48, 2). Blue-green algae form with protozoa and some other organisms a unique group of endosymbioses called syncyanoses; the resulting morphological complex of two organisms is called c and a n o-m, and blue-green algae in it are called c and a-nells (Fig. 48, 3).[...]

In soil samples from the areas of phosphogypsum dumps in May 2004, as well as during the same period in 2003, blue-green and yellow-green algae were absent. In July 2004, Cyanophyta and Xanthophyta were absent. The specific species of this algocenosis were Chloronomala palmelloides Mitra, Scendesmus acutus Meyen.[...]

The phytoplankton of the Nizhny pond was characterized by low species diversity. Representatives of 5 divisions of algae, 14 families and 17 genera were discovered. In total, 20 species of algae were identified: green - 10, euglenophytes - 4, blue-green - 3, diatoms - 2 and yellow-green - 1. The dominant species was Stephanodiscus hantzschii, its biomass varied from 10.32 to 14.60 mg/l.[...]

Approximately the same number of species were identified in air and snow (35 and 39, respectively). In terms of ecobiomorphs, Ch-form algae clearly predominated. These are single-celled representatives of green and yellow-green algae, species of the genera Chlorella, Chlorococcum, Myrmecia, Pleurochloris that tolerate extreme conditions well. Often these species are found on soil lumps or surface deposits (Shtina et al., 1981). Therefore, it is quite possible for these algae to get into the air along with soil particles that are lifted by strong gusts of wind. A pairwise comparison of the snow algal flora of the studied areas of the city using the Sørensen coefficient shows that, unlike soil samples, the snow samples showed great similarity. This pattern appeared regardless of the distance between sampling points.[...]

The Chrysotrichaceae class combines freshwater, less often brackish-water and marine forms. This is the most highly organized group of golden algae, whose representatives are similar in appearance to the ulothrixaceae from the department of green algae and the heterothrixaceae from the department of yellow-green algae. Some of them are similar to the most simply structured representatives of brown algae.[...]

Seedlings grown in the absence of light are called etiolated. Such seedlings, as a rule, are characterized by a changed shape (elongated stems, rotten leaves) and a weak yellow color (there is no chlorophyll in them). At the same time, it has been known since the time of Sachs (1864) that in some cases chlorophyll is formed in the absence of light. The ability to form chlorophyll in the dark is characteristic of plants at the lower stage of the evolutionary process. Thus, under favorable nutritional conditions, pepotry bacteria can synthesize a yellow-green pigment in the dark - bacteriochlorophyll. Blue-green algae, when supplied with sufficient organic matter, grow and form pigments in the dark.[...]

Soil samples from May - July 2004 from the plant territory were characterized by a general decrease in species composition: a total of 12 species and intraspecific taxa were identified, which may be due to an increase in production capacity. In May, there were no yellow-green algae, blue-green algae were represented by 2 species (17%), diatoms - 3 species (25%), green - 7 species (58%). In July, the picture remained virtually unchanged: we identified one species of yellow-green algae (9%), one species of diatoms (9%), 2 species of blue-green algae (18%) and 7 (64%) species of green algae.[ .. .]

Only two species of lichens, representatives of the genus Verrucaria, have the yellow-green algae Heterococcus as their phycobiont. Brown algae are also rare in lichen thalli. The brown algae Petroderma was found in the thallus of one of the species of the same genus Verrucaria.

The department of golden algae (Chrysophyta) includes about 400 species.

Set of photosynthetic pigments in golden algae almost the same as that of brown, diatoms and pyrophytic algae. Most golden algae have a monad shape, i.e. they are unicellular, motile and equipped with 1-2 flagella. Usually monads are naked (there is no cell wall), but many species carry calcareous bodies under the cell membrane - coccoliths or an internal skeleton of silica (Fig. 1). Reproduction is asexual (by division and zoospores). The sexual process is known only in a few species.

Habitats

Golden algae live mainly in clean fresh waters; characteristic of acidic waters of sphagnum bogs. Until recently, golden algae were considered primarily a freshwater group, but they have turned out to make a significant contribution to the productivity of marine phytoplankton. Distributed throughout the globe, but are more common in temperate latitudes.

It is not easy to study golden algae, since many representatives of the department, in particular coccolithophores (Fig. 1a), are very small organisms with a diameter of about 25-30 microns, so they are not captured by the usual planktonic network, and the structure of coccoliths can only be studied using an electron microscope.

Coccolithophores are important in the formation of bottom calcareous sediments (chalk consists of 50-75% of their skeletons - coccoliths). In addition, they prevent the greenhouse effect by binding excess carbon dioxide in the form of calcium carbonate when building “houses” from coccoliths.

Golden algae are one of the oldest groups of algae. Representatives of golden algae were found already in Cambrian sediments about 500-600 million years old. It is possible that golden algae are the ancestors of diatoms and brown algae.

Rice. 1. Golden algae: a-d) coccolithophores; d-g) silicoflagellates

Department of yellow-green algae

The department of yellow-green algae (Xanthophyta) includes about 500 species of unicellular, colonial, multicellular and noncellular algae. A set of photosynthetic pigments of yellow-green algae is represented by chlorophyll A, chlorophyll With and carotenoids, but unlike golden algae, representatives of this department do not have fucoxanthin.

Golden algae are found in reservoirs with fresh and salt water, as well as on land - in the soil, on stones; are an important component of both plankton and benthos.

The most famous representative of the department is voucheria, or water felt(Vaucheria), lives in fresh, brackish and sea waters. Has a noncellular thallus, i.e. It is one giant multinucleated cell. When reproducing asexually, Voucheria forms multiflagellate, multinucleated zoospores. The sexual process is pronounced oogamy (Fig. 2).

Rice. 2. Life cycle of Vaucheria: a) asexual reproduction; b) sexual reproduction; 1 - mother plant; 2 - zoosporangium; 3—zoospore release; 4 - zoospore; 5—zoospore germination; 6 - antheridium; 7 - oogonia; 8 - sperm; 9 - egg; 10 - zygote