Marine red algae representatives. The importance of algae in nature and human life
General characteristics of the Red algae department
Red algae, or purple algae (Rhodophyta ) - algae department, characteristic feature which is the absence of flagellar stages. Bagryanka is the largest and peculiar group among bottom seaweeds. The Red Algae department has about 4 thousand species.
General signs. The uniqueness of scarlet flowers is determined, first of all, by the set of pigments. In addition to green pigment, red algae also contains red, blue and yellow ones. The characteristic color of red algae is determined primarily by the presence of special red and blue pigments - phycobilins, which are found only in them and cyanobacteria. Various combinations of phycobilin with yellow and green pigments can cause pink, red, orange-yellow, violet or almost black coloring. Red pigments allow these algae to capture weak light at depths of 200-250 m. They are perhaps the only algae living at such depths. The Red Algae department comprises predominantly multicellular organisms; only some species of these algae are unicellular or colonial. The thallus of most purple plants looks like beautiful bushes or plates. Cell covers are represented by several layers, which contain cellulose, pectin substances and agar-agar. The body of many red algae is very delicate and fragile. But there is a part of scarlet mushrooms that deposit calcium carbonate in their cell walls. Red algae store a special substance - purple starch, which is deposited in the cytoplasm. Red algae reproduce vegetatively - by parts of the thallus and additional “shoots” that can grow from creeping threads or soles, Asexually - with the help of spores, and polo - with the participation of gametes. It is interesting that none of their cells, including germ cells, have flagella.
Distribution and diversity. These algae are most common in warm sea waters, although many species also live in cold regions of the globe. Less than a hundred species are found in fresh water bodies (for example, algae of the genus Batrachospermum), where they love cold, fluid waters. Among the red algae there are also terrestrial inhabitants, which can be found in the form of reddish mucous deposits on the walls of greenhouses, during wet soil, along the edges of puddles in the garden (for example, single-celled algae of the genus Porphyridium). Almost all red algae are usually attached to rocks or other algae, so they have rhizoids or soles. With the help of phycobilin, scarlet plants are well adapted to absorb blue and violet rays, which penetrate to great depths. In 1984, Coraline red algae
was found at a depth of 268 m, which is a record mark for photosynthetic organisms. This is almost 100 m below the depth where sunlight usually penetrates. The cell walls of most red algae contain agar, which makes them flexible and slippery to the touch. Many scarlet shells deposit mineral salts in their shells to strengthen them, so they are hard as stone.
The most famous red algae is porphyra, batrachospermum, nemalion, lithotamnion, Coralina, phyllophora, ahnfeltsia, calitamnion, deleseria and etc. Purple the plates look pink-purple with smooth or wavy edges, up to several tens of centimeters in length and up to 10-20 cm in width. The plate consists of one or two layers of cells and is attached to underwater substrates using the sole. These algae are widespread in both northern and southern seas, where they live in an attached state on stones and rocks. Phyllophora has bushy talom, represented by creeping “shoots”, from which vertical stems rise. The upper part of each stem is flattened, grows along the edges and forms a plate with a thickening in the middle.
Meaning in nature. Purples play a significant role in the life of the sea: they are food for animals, produce oxygen, participate in the processes of self-purification of water, and the like. Coraline algae play an important role in the formation of coral reefs. The productivity of such reefs and their ability to grow in relatively poor nutrients tropical waters directly depends on these algae.
Meaning for a person. Red algae are used as food. For example, porphyry is an edible algae (popular name - red sea lettuce) and is introduced into an industrial culture, which is grown on special marine farms. Red sea salad is considered a delicacy, the taste of which is determined by organic compounds - amino acids. Red algae is also used in medicine. Iodine is obtained from them, and drugs to eliminate heartburn are made from Coraline. And one of the algae of the northern sea - Chondrus - in dry form has long been used as a medicine for diseases of the respiratory tract. Agar-agar is extracted from other scarlet plants, which is used in all microbiological laboratories in the world for growing microbes. It is impossible to do without it and Food Industry. Confectioners use agar to make jelly, marmalade, and sweets, and bakers add a small amount of it to the dough so that bread, loaves, and biscuits do not go stale for a long time. In Ukraine, a substance called “Black Sea agar” is obtained from phyllophora. Along the northwestern coast of the Black Sea, between Odessa and Ochakov, there is a zone where phyllophora forms continuous thickets at a depth of 5-60 m. This is the largest grouping of these plants in the world.
So, the most characteristic signs of scarlet mushrooms are the absence of flagellation stages, red coloration due to phycobilins and the storage of starch by scarlet grass.
The importance of algae in nature and human life
Algae play an important role in the synthesis of organic matter on Earth. In the complex of organisms that carry out the circulation of substances in nature, algae, together with autotrophic bacteria and higher plants, constitute the link of producers, due to which all other non-chlorophyll organisms of the planet exist. Participating in the processes of the cycle of substances in nature, algae are active agents of self-purification of water bodies, as well as primary soil-virgin processes and restoration of soil fertility. In the geological record of our planet, algae also left an imprint in the form of diatomites and limestones. In nature, algae are a source of food for many aquatic life, saturate the water and air layers of the atmosphere with oxygen. Together with bacteria, many bacteria clean water bodies. From the remains of algae after they die, they form rocks. However, algae can also have a negative effect. Yes, when mass reproduction microscopic algae in water bodies causes “water blooms” of green, red, yellow, and brown colors.
From algae, humans extract substances that are used to produce food. Some seaweeds are edible and are enjoyed by many people. Buri and red algae are eaten. Most often they are simply selected from the water, but some are grown on purpose. Buri and green algae are food for animals. In addition, fertilizers are obtained from algae; they are used in medicine to heal wounds and treat colds. Modern preparations from algae are used to treat people who have been exposed to radioactive radiation. Some algae are used to determine the degree of pollution from wastewater and petroleum products. Many algae are convenient objects for scientific research.
So, the enormous importance of algae in nature and for humans is mainly due to the fact that they produce a huge mass of organic matter and produce oxygen.
Landing led to the development of higher plants.
is one of the largest subkingdoms of algae, which has more than 5,000 different species. They are almost exclusively multicellular seaweeds, and many of the common varieties of algae consumed by humans belong to them. They can be contrasted primarily with brown and green algae, but should not be confused with the subkingdom Dinoflagellata, which includes the algae that cause the so-called “red tide.”
In many countries around the world, particularly in Asia, many types of red algae are consumed as food. Typically, red algae have a high nutritional value, and, like other algae, are extremely easy to grow, making them an ideal food source as they can produce huge quantities at minimal cost.
One of the very famous varieties of red algae that is cultivated all over the world, especially in Japan, is nori. Nori plays an important role in cooking, in particular sushi and rolls.
Another type of edible red algae is one that grows in Atlantic Ocean Irish moss, or Chondrus crispus. It is one of the main sources of carrageenan and is used in many foods and beverages, both as a stabilizer and as a thickener. This substance can be found in products such as ice cream and non-dairy frozen desserts. In the Caribbean, this red algae is used directly to produce a drink from sweetened and condensed milk or to flavor ice.
Red algae may also be referred to when referring to red slimy algae. These are, essentially, not even algae, but cyanobacteria. Often, red slimy algae, which have existed for over three billion years, are seen as a link between bacteria and true algae. Although red slimy algae are not particularly physically attractive, they are among the most important creatures on the planet. These algae are responsible for producing colossal amounts of oxygen, so it is believed that if red slimy algae did not exist, the Earth's sky would not be blue.
True red algae are red in color because they all contain a specific pigment, phycoerythrin. This pigment absorbs blue light and reflects red light. This evolutionary mechanism allows red algae to exist at slightly greater depths than other types of algae because blue light penetrates deeper into the water than long-wavelength light. Although some varieties of red algae have a deep red color, making them clearly a member of this subkingdom, others contain relatively little phycoerythrin and high amounts of chlorophyll, which can make them appear more blue or green.
Exist certain types algae, which play a crucial role in the formation of reefs. IN Pacific Ocean There are atolls that owe their development to red algae rather than to corals. These types of algae, known as coralline algae, create a layer of carbonate around themselves, much like coral. This contributes to the formation of reefs around them, which can reach enormous sizes.
(Bangiophyceae) and florideaceae (Florideophyceae), about 20 orders, more than 600 genera and 6000 species. Mostly macroscopic algae (length from 1 mm to 1 m) of various shapes. Among the primitive red algae there are a few freshwater (Batrachospermum) and terrestrial (Porphyridium) species (about 20 genera and 150 species). Fossil remains of red algae have been known since the Cambrian.
The overwhelming majority of red algae are multicellular organisms of parenchymal (porphyry and bangia - Bangia) or complex anatomical structure, which is based on a system of branched filaments, sometimes unicellular, colonial. Cell walls consist of cellulose microfibers, less commonly xylan (porphyry), and a mucous amorphous part containing pectin substances, including various galactans (agar, carrageenan, etc.); in some representatives, the cell walls are calcified due to deposits of calcite (corallina) or aragonite (liagora). In many red algae, daughter cells are connected by pores, which are closed by plugs of proteins. The chemical structure of the latter is specific to certain groups of red algae. In highly organized floridaeids, in addition to primary pores, secondary pore connections are formed between neighboring cells. Red algae lack flagellar cells. Chloroplasts are surrounded by their own 2-membrane membrane, thylakoids are solitary, not collected into lamellae, equidistant.
Red algae reproduce by vegetative, asexual and sexual means. Vegetative reproduction predominates in primitive bangiaceae (Porphyridium) and unattached Florideaceae (Anfeltia, Phyllophora). Asexual reproduction by monospores (in representatives of the orders Bangiales, Acrochaetiales) or, in most floridaeids, by tetraspores (4 in special sporangia). Sexual reproduction is oogamy. The oogonia (female genital organ), or carpogon, has a tubular outgrowth - trichogyne for trapping sperm. The fertilized carpogon (zygote) undergoes complex development, as a result of which a special filamentous structure (gonimoblast) is formed, giving rise to many carpospores that germinate into the sporophyte. All spores and gametes are naked and motionless. Sporophyte and gametophytes are morphologically similar (polysiphonia), less often different (porphyra).
Red algae are typical inhabitants of the sea shelf, penetrating the great depths(more than 200 m), often dominate communities and determine the nature of bottom vegetation, serving as food and habitat for marine animals. Distributed throughout the World Ocean, most diversely represented in tropical seas, to a lesser extent - in the polar ones. Red algae are used mainly for food (porphyra), for the production of agar (anfeltia, gelidium - Gelidium, gracilaria - Gracilaria) and other gelling carbohydrates, including carrageenan (chondrus), agaroid (phyllophora), widely used in the food industry and winemaking , microbiology, medicine. As a result of fishing and mariculture, red algae produce about 7,000 tons of agar annually in the world. In Russia, it is mined in the Far East and the White Sea from anfeltia and gracilaria.
Lit.: Vinogradova K. L. Department of red algae (Rhodophyta) // Plant life. M., 1977. T. 3: Algae. Lichens.
K. L. Vinogradova.
Red algae are also called purple algae.
Red algae vary in size: most often it is large plants, although there are very microscopic unicellular species.
Filamentous and pseudoparenchyma species predominate, but red algae do not have true parenchyma forms. Parenchyma is a special internal tissue with vessels, characteristic of higher plants and animals.
Red algae - structure
Red algae, like most other plants, have chloroplasts containing chlorophyll, a green pigment. But, besides them, red algae have organelles containing red and yellow-orange pigments. This is what gives them their red color, masking the chlorophyll.
Thanks to this, these algae can absorb light from almost the entire visible spectrum. However, not all red algae are red; many species have other variants, including the “standard” blue-green color for plants.
Reproduction
Red algae are characterized by a fairly developed reproduction system for their group of plants. The sexual process is always oogamous, that is, sperm and eggs differ significantly in size and structure. However, the reproductive cells of red algae never have flagella.
After fertilization, a zygote is formed, which develops directly on the gametophyte, that is, a sporophyte (asexual generation) is not formed in red algae. The zygote forms carpospores, from which new plants grow. Some red algae (such as porphyra) are capable of vegetative reproduction.
Where do they live?
Red algae inhabit the seas and oceans in different parts globe. In Russia, they grow in the northern seas - the Barents and White. These algae “graze” in the littoral and sublittoral zones - coastal areas of the seas that are flooded during high tide and dry out at low tide.
Red algae found in abundance different applications, For example:
- Some red algae are eaten;
- These algae serve as a source of agar-agar, a jelly-forming substance used in the production of various products (marmalade, sweets, sauces, etc.);
- Some red algae are used medicinally.
Agar-agar is a real “vegetable gelatin”. Thanks to this substance, strict vegetarians now have access to products that are traditionally produced from gelatin (a substance of animal origin). At the same time, agar-agar is denser than animal gelatin, and products made from it are stronger, harder and more stretchable.
Porphyra is a widespread dish, popular both in the West and in the East. In the DPRK, its cultivation has recently become an important part of state program to fight hunger.
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- Introduction
- 1. General characteristics of red algae
- 1.1 Ecology, distribution, habitats
- 1.2 Classification of red algae
- 1.3 Structure of red algae
- 1.4 Propagation of red algae
- 2. Main classes of red algae
- 2.1 Banguiaceae. Purple
- 2.2 Florida
- Conclusion
- Bibliography
Introduction
Red algae (Rhodophyta) is a division of algae characterized by the red color of the thallus, due to the presence of specific biliprotein pigments - red phycoerythrin and blue phycocyanin. The product of assimilation is purple starch. Red algae are divided into two classes - Bangiophyceae and Florideophyceae and number over 600 genera and 4000 species (the vast majority are marine). Red algae are multicellular, complexly divided plants, but smaller than brown algae(few species reach 2 m). The cells of red algae are covered with a slimy membrane, from which jelly is obtained - agar-agar containing pectin, sugars, and proteins. The predominant pigment in chromatophores is phycoerythrin (red). red algae propagation of porphyry
The purpose of the course work is to examine issues related to red algae.
· ecology, distribution, habitats of red algae;
· classification of red algae;
· structure of red algae;
· proliferation of red algae;
· main classes of red algae (Bangium (Porphyra); Florida).
1. General characteristics of red algae
1.1 Ecology, distribution, habitats
A variety of red algae, or scarlet algae, are found in large quantities in the seas and oceans. This group includes about 4000 species. These are the most structurally perfect algae. Most purple algae range in size from a few centimeters to a meter, and in some cases up to 50 m. But unicellular red algae are also found. They are always attached to stones, shells and other underwater objects with the help of thread-like outgrowths - rhizoids. They also live in the northern seas, but prefer the warm southern ones. Red algae live at different depths, including deep ones (up to 260 m). Some scarlet fish are found in fresh water, mainly in streams and clear, fast rivers. Batrachospermum is a gelatinous, highly branched algae consisting of brownish or reddish bead-like cells. Lemanea is a brush-like form that often grows in fast-flowing rivers and waterfalls, where its thalli are attached to rocks. Audouinella is a filamentous algae found in small rivers. Irish moss (Chondrus cripus) is a common marine macrophyte.
In some species of red algae, called stone algae (lithothamnia), the thallus is heavily impregnated with calcium carbonate. Such scarlet fish, along with corals, participate in the formation of coral reefs. But unlike corals, they are also common in the North, forming red-pink crusts on the rocky bottom in the Barents and White Seas in places with strong currents.
One of the algae living in the North Sea, chondrius, in dry form has long been used as a medicine for respiratory diseases. Agar-agar is obtained from other scarlet plants, which is used in all microbiological laboratories in the world to obtain pure cultures of microbes. However, they cannot do without it in the food industry and even in the production of film. Confectioners and bakers add a small amount of agar-agar to the dough so that cakes, biscuits, and bread do not go stale longer.
The reserves of red algae are huge. Only one of the scarlet plants - Phyllophora - regularly creates entire algal plantations in our country. In the Black Sea between Odessa and the mouth of the Danube, a plantation with an area of 10 thousand square kilometers annually produces a harvest of 10 million tons, which is approximately 10 tons per hectare. In addition to agar-agar, iodine is also extracted from it.
In Japan, China, Korea, and the islands of Oceania, they are used to prepare salads, seasonings, soups, and even candies. In Japan they are grown, especially porphyry algae. But the role of red algae in industry is incomparably more important. From them agar-agar is obtained - a mixture of high-molecular carbohydrates, often with attached sulfuric acid residues. Agar dissolved in hot water forms a dense jelly after cooling. Agar is used in the production of marmalade, marshmallows, non-sugared jam and non-staling bread; it is added to ice cream and jelly. It also gives paper and fabrics a glossy finish. The role of agar in microbiology is even more important: it is used to prepare solid media for growing individual colonies of microorganisms. IN Lately It became known that sulfated carbohydrates from red algae - carrageens - suppress the growth of the virus that causes AIDS.
Red algae play an important role in marine life because they synthesize organic substances at depths where other algae cannot live. Many marine animals feed on them.
1. 2 Classification red algae
Systematically, algae are a collection of several separate groups of plants, probably independent in their origin and evolution. The division of algae into groups mainly coincides with the nature of their color, which, in turn, is associated with a set of pigments, and is also based on general structural features. With this approach, 10 groups of algae are distinguished: blue-green (Cyanophyta), pyrophyta (Pyrrophyta), golden (Chrysophyta), diatoms (Bacillariophyta), yellow-green (Xanthophyta), brown (Phaeophyta), red (Rhodophyta), euglenophyta (Euglenophyta), green (Chlorophyta) and charophytes (Charophyta) Garibova P.V. and others. Course of lower plants. - M.: Higher School, 2001. - P.41.
In our country, most taxonomists adhere to the point of view of dividing all organisms into four kingdoms - bacteria, fungi, plants and animals. In this case, algae proper include all of the above groups (divisions in the plant kingdom), except for the blue-green ones. The latter, being prokaryotic organisms, fall into the kingdom of bacteria.
There are other classifications. For example, some foreign taxonomists divide all living organisms into five kingdoms: Monera (prenuclear), Protista (eukaryotic single-celled or consisting of many cells not differentiated into tissues), Animalia (animals), Fungi (fungi), Plantae (plants). In this case, blue-green algae also belong to the kingdom Monera, while the remaining divisions of algae fall into the kingdom Protista, since, lacking differentiated tissues and organs, they cannot be considered plants. There is also a point of view according to which different groups of algae receive the rank of separate kingdoms.
The group of algae includes lower plants, the body of which is not divided into organs and tissues and is called a thallus (thallus). Algae are extremely diverse and, systematically, represent a combination of several separate plant divisions, probably independent in their origin and evolution. This is evidenced by significant differences in the set of pigments in different groups algae, details of the fine structure of chloroplasts (which in algae are often called chromatophores), products of photosynthesis that accumulate in the cell, in the structure of the flagellar apparatus, etc.
The department of red algae, or purple algae, (Rhodophyta) includes more than 600 genera and about 4000 species. The oldest red algae, found in Cambrian sediments, are about 550 million years old.
Some taxonomists distinguish this group into a separate subkingdom in the plant kingdom, since scarlet plants have a number of features that significantly distinguish them from other eukaryotic algae. In addition to chlorophylls a and d and carotenoids, their chromatophores also contain a number of water-soluble pigments - phycobilins: phycoerythrins (red), phycocyanins and allophycocyanin (blue). As a result, the color of the thallus varies from crimson-red (if phyco-erythrin predominates) to steel-blue (with an excess of phycocyanin). The reserve polysaccharide of red algae is “purple starch”, the grains of which are deposited in the cytoplasm outside the chloroplasts. In its structure, this polysaccharide is closer to amylopectin and glycogen than to starch.
The department is divided into two classes: Bangiophyceae and Florideophyceae.
The Floridea class (Florideophyceae) unites multicellular, complexly organized forms. Includes the following subclasses and orders:
Subclass Hildenbrandiaceae - Hildenbrandiophycidae
Order Hildenbrandiales
Subclass nemaliophycidae - Nemaliophycidae
Order coralline - Corallinales
Order Batrachospermales - Batrachospermales
Thorea order - Thoreales
Order nemaliales - Nemaliales
Order Acrochaetiales - Acrochaetiales
Order Palmariales - Palmariales
Subclass Ahnfeltiophycidae - Ahnfeltiophycidae
Order Ahnfeltiales - Ahnfeltiales
Subclass rhodymeniophycidae - Rhodymeniophycidae
Order Gelidiales
Order Bonnemaisoniales - Bonnemaisoniales
Order Gracilariales - Gracilariales
Order Gigartinales - Gigartinales
Order Rhodymeniales
Order Plocamiales
Order Ceramiaceae - Ceramiales
1. 3 The structure of red algae
The composition of the cell wall of scars includes pectins and hemicelluloses, which can swell greatly and merge into a common mucous mass containing protoplasts. Often, mucous substances glue the threads of the thallus, which makes them slippery to the touch. The cell walls and intercellular spaces of many scarlet plants contain phycocolloids - sulfur-containing polysaccharides that are widely used by humans in economic activities. The most famous of them are agar, carrageenin, agaroids Garibova L.V. etc. Algae, lichens and bryophytes. - M.: Mysl, 1998. - P.40. Many purple moths deposit calcium carbonate in their cell walls, which gives them rigidity.
In most red algae, thalli are formed by intertwining multicellular filaments attached to the substrate with the help of rhizoids; less often in this group one can find unicellular (porphyridium) and lamellar (porphyra) forms. The size of the thalli of the scarlet mushrooms ranges from several centimeters to a meter.
For the most part, red algae are inhabitants of the seas, where they are always attached to stones, shells and other objects at the bottom. Sometimes scarlet fish penetrate to very great depths. One of the species of these algae was discovered near the Bahamas at a depth of 260 m (the illumination at such a depth is several thousand times less than at the surface of the sea). At the same time, algae of the same species growing deeper usually have a brighter color - for example, bright crimson in depth and yellowish in shallow water.
One of typical representatives crimson - callithamnion corymbosum - forms graceful bushes of bright pink color up to 10 cm in height, consisting of highly branched threads. Nemalion grows on rocks in the seas, the slimy pale pink cords of which reach 25 cm in length and 5 mm in thickness. In species of the genus Delesseria, the thalli look like bright red leaves - they were formed by the fusion of lateral branches of the main axis. In species of the genus Corallina, common in warm seas, the thalli consist of segments heavily impregnated with lime, connected to each other by joints with a small content of lime, which gives the entire plant flexibility, which helps withstand the action of waves and grow in places of strong surf.
1. 4 Propagation of red algae
Vegetative propagation by fragmentation of the thallus; It is especially often observed in habitats where environmental factors (temperature, light) are unfavorable for reproduction by spores.
Asexual reproduction is carried out through immobile cells developing from the contents of the sporangium, one (monospores) or four (tetraspores),
Tetraspores form on diploid asexual plants - Tetrasportonsillitis (tetrasporangeal phase). IN Tetrasporangia meiosis occurs before the formation of tetraspores. The arrangement of tetraspores in a tetrasporangium can be cruciform (gelidium, chondrius), row (coralline, durenea) or at the corners of a tetrahedron (ceramial).
Vegetative propagation is not typical for red algae.
After fertilization, the resulting zygote undergoes a complex development directly on the gametophyte and gives rise to special spores called carpospores, which are formed in carposporangia, while in many other algae the zygote develops into a sporophyte, giving rise to a new form of plant development. The life cycle of red algae is isomorphic or heteromorphic diplo-haplobiont Botany: plant taxonomy. / Ed. M.I. Ashmarina. - Tomsk, 2004. - P.31.
Oogamy consists in the fusion of a large, immobile, flagellated egg cell with a small male one - a spermatozoon equipped with a flagellum or a flagellated spermatium. Oogamy is common in algae with a complex multicellular thallus, with male and female reproductive cells developing in special organs - antheridia And oogonia, usually sharply different from vegetative cells.
Female organ - karpogoi- in most red algae (florideophyceae) it consists of an expanded buttal part - the abdomen containing the egg, and a process - trichogynes(the latter is absent in Bangificaceae). Trichogyne either does not contain a nucleus at all, or it degenerates by the time of fertilization. Carpogon usually develops on a special short one, consisting of 3-4, less often 7-9 cells carpogthis branch, which in turn sits on supporting (carryingcabbage soup) cage. Antheridia ( stolematangia)- usually small colorless cells, the contents of which are released in the form of small naked male fertilizing elements devoid of flagella stoleManziev. The spermatozoa dropped from the antheridia are passively transported by water currents and adhere to the trichogyne. At the point of contact between sperm and trichogynes, their walls dissolve, and the sperm nucleus moves along the trichogyne to the abdominal part of the carpogon. where it merges with the female core. These data from classical studies of the end of the last century, which have retained their significance to this day, can be supplemented with some observations recent years. Thus, in 1984, new data were obtained on the dynamics of the sexual process in some red algae. Under experimental conditions, Callithamnion cordaium It was possible to show that mature carpogons (their maturation occurs within four days after the initiation of the carpogonal branch) are susceptible to sperm within 3 hours. The process of gamete fusion itself, including the phases known from classical works (attachment of sperm to trichogyne; plasmogamy, downward transfer of the sperm nucleus according to trichogyne and karyogamy), lasts 5-10 hours. After fertilization, the basal part of the carpogon is separated by a septum from the trichogyne, which dies and undergoes further development, leading to the formation of carpospores in most red algae. The details of this development are of important systematic importance. In some red algae, the contents of the zygote (fertilized carpogonum) are directly divided to form immobile bare spores carposporus, in others, multicellular branching filaments grow from the fertilized carpogon (or from its daughter cell) gonimoblasYou, cells that turn into carposporangee, producing one carpospore. Finally, in most red algae, gonimoblasts do not develop directly from the abdomen of the fertilized carpogonum, but from special auxiliary auxiliary cells. The latter can be removed from the carpogon or located on the thallus and its immediate vicinity. If the auxiliary cells are removed from the carpogon, hyphae-shaped ones grow from its abdomen after fertilization, without transverse cell partitions connecting or ooblastemns threads Their appearance is preceded by mitotic divisions of the copulation nucleus and thus they contain diploid nuclei. Regional filaments grow To auxiliary cells, at the point of contact the membranes dissolve, and the tip of the ooblastic filament and the auxillary cell merge. The diploid nucleus of the ooblastoma filament divides, one of the daughter nuclei is transferred to the auxiliary cell, and the other remains in the ooblastema filament, which can grow to the next auxiliary cell, etc.
The combination of an auxiliary cell (or cells) with a carpogon is called goodnesswe drink. There is no need for the formation of long oblastem filaments connecting the carpogon and auxiliary cells; the auxiliary cell simply merges with the abdomen of the fertilized carpogon, after which gonimoblasts with carpospores develop from it. Carposporangia are often arranged in close groups - cystocarp, which in many representatives are covered with a pseudoparenchymatous membrane, developing from cells adjacent to the carpogon Raven P. et al. Modern botany. - M.: Mir, 2003. - P.66.
2. Main classes of red algae
2.1 Banguiaceae. Purple
The class Bangiaceae unites unicellular, colonial and multicellular forms of parenchymal structure. Their growth is diffuse, as a result of the division of all cells of the thallus. Banguiaceae cells are mononucleate with one stellate chloroplast and one central pyrenoid. In many representatives of the class, the chloroplast has an axial position, which is considered more primitive compared to the wall position. Sexual reproduction is known only among highly organized representatives of the class. Sex cells are formed as a result of the transformation of a vegetative cell. The zygote undergoes division and turns into carpospores. Asexual reproduction is carried out by monospores, less often by akinetes. Monospores and carpospores are glabrous and capable of amoeboid movements. Most representatives of the class, especially among the primitive ones, are freshwater and terrestrial inhabitants. Marine forms distributed in the coastal zone of all seas, but in temperate latitudes they are more abundant than in the tropics.
The Banguiidae class is small in volume. It contains about 20 genera and 70 species. Taxonomists divide it into 6 orders, the most important of which is the Bangiales order. All representatives of the class can be divided into two groups, which, apparently, represent two different branches of evolution. The first includes multicellular filamentous and lamellar forms, distributed mainly in the sea. The second group consists of unicellular and colonial algae, more often found in freshwater and terrestrial habitats. If the first group belongs to typical purple algae, then the second, according to some characteristics, strongly gravitates toward blue-green algae.
Main representatives: Porphyridium, Chrootece, Goniotrichum, Asterocytis, Porphyra.
The most famous unicellular algae from the order Porphyridiales is Porphyridium. The round cells of this algae are usually collected in mucous colonies, which cover the soil and damp walls in the form of blood-red films.
The other one unicellular algae-- Chroothece, also growing on the soil, has a very strong development of the mucous membrane. It has the appearance of a layered stalk, more than 50 times the length of the cell.
In Goniotrichum, as well as in Asterocytis, the filamentous thallus is already a permanent feature. In most species, the cells are collected in single-row filamentous colonies, and only one of the Bangies is characterized by sexual reproduction. Spermatangia in Porphyra and Bangia are formed as a result of repeated divisions of vegetative cells, so that from 32 to 128 spermatangia develop in one cell, each of which contains one sperm. Ordinary vegetative cells turn into oogonia, or carpogons, each cell into one carpogon.
Banguid class inside division Rhodophyta constitutes a very isolated group, possessing a number of primitive features. Diffuse growth, the formation of reproductive organs in any cell of the thallus and the lack of specialization in their structure, the direct transformation of the zygote into carpospores, the absence of a typical trichogyne - all this indicates the difference between Bangiaceae and Florideaceae. Some scientists considered these differences to be so fundamental that they isolated the bangiaceae from the red algae department and tried to bring them closer to some blue-green and even green algae. But, on the other hand, one cannot ignore the important similarities between both classes. They have the same set of pigments, reserve substances, the character of spermatozoa and carpospores. It is interesting to note that one of the important distinctive features Between them, the absence of primary and secondary pores at the junction of cells has always been considered. However, upon closer examination, many bangieids exhibit pores typical of red algae. This undoubtedly testifies to the close phylogenetic relationship of all purple frogs. In addition, many more similarities with Bangiaceae can be found in primitive floridaeids. They have pyrenoids and a stellate chloroplast, one nucleus, and their spores are also capable of amoeboid movement. Therefore, it is logical to assume that all red algae are the same in their origin.
2.2 Florida
The class unites multicellular, complexly organized forms. Cells are mononucleate, less often multinucleate with wall chloroplasts. Sexual reproduction is characteristic of all floridae; if it is absent, then only with secondary loss. Some representatives are known to reproduce asexually by spores. Most species of the class are typical marine inhabitants, distributed throughout the globe.
Main representatives: freshwater Batrachospermum and Lemanea, marine Melobesia, Lithotamnion, Corallina.
The Floridian class is divided into six orders based on the developmental characteristics of the zygote and the structure of the auxillary system:
Order HELIDIUM
Order GIGARTINE
Order CRYPTONEMIUM
Order NON-MALLIUM
Order GENERAL
Order CERAMIUM
Each order includes algae that are very diverse in morphological and anatomical structure.
Order Gelidiales Gelidiales are a small, well-defined group of red algae. It contains only one family and 8 genera. Auxillary cells, as in non-maliaceae, are absent, but even before fertilization, numerous small-celled filaments are formed next to the carpogonal branch. This is a special nourishing tissue in which gonimoblast threads develop.
Helidium cells are multinucleated, contain many lamellar chloroplasts and lack pyrenoids. Gelidium reproduces sexually and asexually. At the same time, it is possible to distinguish gametophytes from sporophytes only by their reproductive organs.
Order GIGARTINALES Gigartinales are an extremely diverse group with unclear boundaries. This diversity is manifested in the external and internal structure, in the structure of the reproductive organs, and in the features of the development of the gonimoblast. The very number of families included in the order - and there are 21 of them - speaks of its great heterogeneity. The only criterion for distinguishing order is that the auxillary cell in these algae is an ordinary thallus cell.
As these algae are studied, the boundaries between these orders become less and less clear, and the definition of these boundaries is often accessible only to experienced specialists. There is a constant process of moving births from order to order. There are often cases when the details of the development of a fertilized carpogon are very difficult to unravel and explain, and different researchers can see different things on the same microscopic specimen. Apparently, it is true that the stability of the existing classification of red algae is illusory and that of all orders, only one - the Ceramiaceae - is sufficiently well delimited.
Order Cryptonemiales Cryptonemiales already have special auxillary cells. They are laid before fertilization on special additional branches at a distance from the carpogonal branches or in close proximity to them. Gonimoblast threads develop from auxillary cells after their fusion with the carpogon. The thallus of cryptonemiaceae has a different shape (from cylindrical to lamellar and crust-shaped) and a different anatomical structure (both uniaxial and multiaxial types). A whole group of algae has a calcified thallus. The cells are mononucleate and multinucleate, with one or more lamellar or lenticular chloroplasts, lacking pyrenoids. Growth is carried out by one or several apical cells; a special meristem is involved in the formation of the thallus of a number of algae.
Cryptonemiaceae have an alternation of gametophyte and tetrasporophyte, similar in appearance and internal structure. Tetrasporangia, cruciformly or zonally divided, develop differently. Carpogonous branches are simple or branched, usually multicellular; they arise separately from each other or several together in sori, nematecia or conceptacles. After the ceramides, the cryptonemias are the most large order red algae. It includes 13 families, 110 genera and more than 900 species distributed throughout the world's oceans.
Order Nemaliales The order Nemaliales unites organisms that lack auxillary cells. Gonimoblast threads develop directly from the fertilized carpogon or from the underlying cell after the carpogon nucleus has passed into it. Non-maliaceae also do not have special feeding cells. In complexly organized forms, during or after fertilization, the cells of the carpogonal branch and the carrier cell merge in a variety of combinations. The order Nemaliaceae is the most primitive group of red algae. It unites 8 families, which can be divided into two groups. In the first group, the thallus has a single-axial structure, in the second - it is built according to a multi-axial type. Almost all Floridians that live in fresh waters, belong to non-maliaceous algae.
Order Rhodymeniales - a small, fairly well-demarcated order, occupying a separate systematic position in the Florida class. Basics distinctive property Rodimeniaceae is that the auxillary cell, which is formed shortly before fertilization, is a derivative of the carrier cell of the carpogonal branch. All rhodomeniaceae have a procarp - the auxillary and carpogonal branches are a single formation. From the carrier cell, a carpogonal branch develops, always three- or four-celled, and a two-celled auxillary branch, the upper cell of which serves as an auxillary one. Before fertilization, the auxillary cell is poorly distinguishable, but after it it greatly enlarges and is filled with thick plasmatic contents. All algae of the order are constructed according to the multi-axial type. Growth occurs as a result of the activity of apical cells, as well as apical or marginal meristems. The order is divided into two families, differing in the features of their anatomical structure. The Champiaceae family is characterized by a hollow thallus, with the cavity delimited by long, narrow cellular filaments. Tetrasporangia are divided tetrahedrally, some genera have polyspores. Tetrasporangia are divided crosswise. Despite its small volume, the order has an extremely wide range. Rhodomeniaceae are distributed throughout all seas from the tropics to the Arctic Ocean, but they are still most abundantly represented in warm seas.
Order CERAMIALES (Ceramiales) In terms of volume, the Ceramiaceae are much superior to all other orders in the Florideaceae class. Suffice it to say that they unite more than 250 genera and about 1,500 species. But, despite such a large volume, the order is a well-defined group, which is divided into only 4 clearly defined families. The uniformity of order is manifested primarily in the structure and development of the reproductive organs. All ceramiids are characterized by procarp. The auxillary cell is detached directly from the carrier cell of the four-cell carpogonal branch. The auxillary cell is formed only after fertilization.
While the reproductive system of ceramiids is built according to a single plan, their vegetative organization is diverse. The classification of order is based on this. All ceramics are built using a single-axis type. Of the four families, the Ceramiaceae family is at the lowest stage of development. The other three appear to represent parallel lines of evolution, and it is difficult at present to say which of them ranks at a higher level of organization. Ceramides are distributed throughout the world's oceans, but are especially richly represented in the tropics.
Order Gracilariales The order Gracilariales includes several small genera and one very large one - Gracilaria, more than 100 species of which are widespread in temperate and tropical seas of the globe. Species of gracilaria, as indeed all algae of the order in general, tend to flatten, therefore, in addition to cylindrical ones, there are many forms with a flat, even leaf-shaped, thallus. Gracilaria species in some countries serve as raw materials for the agar industry. Gracilaria plants are tough and cartilaginous. The adult thallus has a “cellular” structure; no traces of a filamentous structure can be traced. The central part consists of large cells, gradually decreasing in size from the outside; the cortex is built from several layers of small cells. The growth of the thallus occurs due to the meristem, which was formed on the basis of a uniaxial structure. True, the central axis cannot be traced even in seedlings; only one apical cell is visible, separating downward segments from its three surfaces. The peculiarities of reproduction are that the auxillary cell is indistinguishable before fertilization. The two-cell carpogonal branch is formed on the cells of the outer cortex. After fertilization, the carpogon fuses with several neighboring cells, forming a massive fusion cell, from which gonimoblast filaments grow, directed towards the surface of the thallus. After fertilization, at the site of procarp formation, the surface cells rapidly divide, forming a thick, small-celled cortex, from which the roof of the cystocarp with a hole in the middle is later formed. Cystocarps scattered throughout the thallus protrude above its surface in the form of small balls. The developing gonimoblast is nourished by the fusion cell and partly by nearby cells of the thallus. Spermatangia in gracilaria are formed in special depressions in the cortex, reminiscent of conceptacles, with a hole at the top. Cross-shaped tetrasporangia are scattered in the crustal layer throughout the thallus.
Order Acrochaetiales These algae have the simplest structure. The thallus consists of freely branched single-row threads. They form bushes of microscopic size (usually up to 5 mm in height), and only as an exception are larger plants up to 25 mm in height. The branching in these bushes is alternating and irregular. Often short lateral branches end in a hair at the apex, but there are many species in which hairs are never formed. Only a few acrochaetia algae grow on the ground - on stones, rocks, etc., but most prefer to settle on other algae and animals. They can be found especially often on kelp algae, hydroids, bryozoans, and mollusks. At the same time, they not only attach to the surface of organisms, but also penetrate into the host tissue.
The structure of the basal part of Acrochaetia varies depending on the nature of the substrate. On a hard substrate, be it stones or algae with a dense structure, pseudoparenchyma soles are more common; on loose substrates, free creeping filaments are found. In general, acrochaetiaceae are characterized by a heterofilamentous structure. It manifests itself most clearly in algae in young state, since with a multi-filamentous structure, a creeping structure usually develops first, from the cells of which vertical shoots arise. The intracellular structure of members of the family is diverse. Here you can find forms with axial and wall chloroplasts, with and without pyrenoids. The shape of chloroplasts is a good indicator for distinguishing genera. In some they are star-shaped, in others they are ribbon-shaped, spirally twisted, in others they are in the form of disks. Asexual reproduction in Acrochaetiaceae is carried out mainly by monospores; tetraspores are observed quite rarely. Sporangia sit on short lateral branches, where they are located singly or 2-3 together. Tetraspores are divided crosswise. Carpogon is a single cell; it is located on the side of the main branches or on short side branches. Occasionally a two-celled carpogonal branch is found. Spermatangia in the form of small rounded cells are located at the top of the lateral branches. After fertilization and the falling off of the trichogyne, the carpogon is divided by transverse septa into several cells, from which a bundle of gonimoblast filaments grows. Not all acrochaetids are characterized by sexual reproduction; some reproduce only asexually, among them many species of Rhodochorton. In nature, Acrochaetiaceae are extremely widespread. For the most part, these are marine organisms known in all the seas of the World Ocean. There are much fewer freshwater species - only 5, they belong to the genus Audouinella. Of the marine inhabitants, the most characteristic and widespread algae of the family is Acrochaetium. About 250 species of this genus are described in the literature. When these species began to be studied in culture, especially their reproduction and development cycles, it was discovered that many former species were nothing more than stages or forms of development in life cycle other types. Another seaweed of the family, Rhodohorton, is distinguished by a coarser and larger thallus, growing, as a rule, on rocky soil. On the surf littoral of our northern seas, Rhodohorton often forms an independent belt, covering the shaded surface of boulders and rocks with a dark red coating. The phylogenetic position of the family Acrochaetiaceae is not entirely clear. Although it is placed as the most simply organized group at the beginning of the entire Floridian system, it is still unknown whether this simplicity indicates the primitiveness of its representatives or is the result of secondary simplification. Recently, it has been discovered that some scarlet plants have stages or generations in their development cycle of exactly the same structure as the acrochaetiaceae. This observation suggests that the family is an artificial group that requires more detailed study. In this regard, it is interesting to emphasize that sexual reproduction is unknown in a number of algae of the family and that they differ markedly in their intracellular structure.
Order Batrachospermales This order is interesting because in it one can trace the first steps in the complication of the organization of the thallus of the purple thallus during the transition from a loose filamentous to a dense structure. Character traits The best way to follow this is by getting acquainted with one of the most famous freshwater scarlets - Batrachospermum. About 50 species of this genus are distributed in all parts of the world. They prefer well-aerated waters of slowly flowing rivers and streams, but they can also be found in the coastal part of lakes, where there are no strong temperature fluctuations. Some even penetrate peat bogs, but are more often found near springs. The soft mucous thallus of batrachospermum consists of a central single-row branched axis. The main branches are densely covered with bunches of short branches of limited growth, arranged in whorls. The structure of Batrachospermum is easy to imagine as a result of the complication and ordering of the structure of Acrochaetiaceae, and this is confirmed by the individual development of Batrachospermum species. First, a thread creeping along the substrate is formed; it branches to form a pseudoparenchyma sole, from the cells of which many vertical single-row shoots arise, morphologically almost indistinguishable from acrochetium. This stage, which is called the acrochetium stage, can exist for quite a long time and even reproduce by monospores. It is no wonder that it is often mistaken for an independent species of acrochetium. The development of this stage is largely determined by environmental conditions. In general, it can be called a shadow form of growth, while the batrachospermum stage is a light form. In this regard, in nature they are confined to different seasons. Batrachospermum shoots develop anywhere in the acrochaetium stage. Their structure belongs to the central-axial type, which in the literature is often called the batrachospermum type. The apical cell of the central axis separates new segments, which quickly grow in length and thickness. On each of these segments, whorls of 4-6 small cells are formed, which gradually grow into bundles of branches of limited growth. The terminal cells of the lateral branches often transform into hairs. The branches in bundles are bound by a large amount of mucus. From the lower cells of branches of limited growth, cellular rhizoid filaments usually arise, descending down the thallus and enveloping the central axis. From these threads additional bundles of branches of limited growth can develop, which, together with the first ones, serve as assimilation threads. Organs asexual reproduction- monosporangia - are very rare on batrachospermum plants; they are much more often formed on immature plants like acrochetium. Sexual reproduction differs in some ways. Trichogyne has a pin-shaped or cylindrical shape, unusual for red algae. Carpogon is formed at the top of branches arising from the lower cells of branches of limited growth. Globular spermatangia develop at the top of the lateral branches, 1-3 on cells that are no different from vegetative ones. Mature gonimoblasts are clearly demarcated formations, immersed in mucus among assimilation threads and densely surrounded by them.
Order CORALLINES (Corallinales) It is characterized by a huge variety of forms. Coralline algae are easy to distinguish from other algae of the order, as well as from all purple algae in general: their thallus is so saturated with lime that they can rather be mistaken for corals or stones than for algae. In addition to calcification, these algae have another peculiar feature: the organs of both sexual and asexual reproduction are formed in special containers - conceptacles, which communicate with external environment one or more holes.
Coralline subfamily (Corallinoideae) Articular corallineaceae are characterized by a vertical branched thallus, in which calcified segments alternate with calcareous joints. In the seas of Russia, coralline and amphiroa are most often found. These are the most important representatives of the subfamily. Each of these genera combines the characteristics the whole group genera and reflects a separate line of evolution.
The genus Corallina includes low plants, very beautiful due to their pinnate and forked branching. The vertical thallus is formed on the basal part, which here is developed to a lesser extent than in the cortical ones, and is much simpler in structure. The segments are always impregnated with lime, although calcification usually does not affect the internal parts and is limited to the bark. The threads of the inner part of the thallus consist of cells of the same size, arranged in transverse rows (on a longitudinal section). Several layers of core cells end at the surface with a single layer of integumentary cells. The latter are absent only above the apical cells that grow in length. The central and core cells often merge with each other. The joint is never calcified and consists of a single row of parallel, long, thick-walled cells. At the beginning of the formation of the joint, it is covered with bark, which subsequently collapses.
Not all tetrasporangium mother cells reach maturity. Some of them remain sterile. Coralline sexual plants are more irregularly branched and more densely covered with concentacules. Spermatangia are formed on the bottom and side walls of the conceptaculum and have a very characteristic shape. They are widened (like a head) at the anterior end and extended into a long narrow tail at the rear.
The genus Amphiroa has fewer species and a more limited geographical distribution. The forked-branched plants of Amphiroa also consist of distinct segments, but in their formation some more primitive features can be traced that bring this genus closer to unsegmented corallines. The cells of the central filaments are arranged in an orderly manner, in arcuate transverse zones, with a zone of long cells alternating with a zone of short ones. Externally, the central bundle is limited by the small cell cortex.
Trying to understand the phylogeny of Cryptonemiaceae, scientists proceed from the fact that various directions of development in order (as well as in the entire class of Florideaceae) are reflected, first of all, in the nature of the structure of the female reproductive system and in the features of the development of the gonimoblast. The main criteria are the presence or absence of a procarp, the number of cells in the carpogonal and auxillary branches, and the place of formation of the auxillary cell. Previously, all families of the order were divided into two groups - those with procarp and those without. But the deeper these algae are studied, the more obvious it becomes that the specialization of the auxillary system can occur independently in different algae. In many families, along with genera in which the carpogonal and auxillary branches are formed separately, one can find genera that already have a more or less developed procarp. According to modern views, one of the important features that is relied upon when constructing the classification of Cryptonemiaceae is the mono- or polycarpogonal nature of the female reproductive system.
The modern classification of order cannot be considered fully developed. The relationship of the order with other purple algae also remains unclear, although there is evidence of similarity of individual Cryptonemiaceae with algae of the order Gigartina.
Conclusion
Red algae (Rhodophyta) is a division of algae characterized by the red color of the thallus, due to the presence of specific biliprotein pigments - red phycoerythrin and blue phycocyanin. The product of assimilation is purple starch. Red algae are divided into two classes - Bangiophyceae and Florideophyceae and number over 600 genera and 4000 species (the vast majority are marine). Red algae are multicellular, complexly divided plants, but smaller than brown algae (few species reach 2 m). The cells of red algae are covered with a slimy membrane, from which jelly is obtained - agar-agar containing pectin, sugars, and proteins. The predominant pigment in chromatophores is phycoerythrin (red).
Systematically, algae are a collection of several separate groups of plants, probably independent in their origin and evolution. The division of algae into groups mainly coincides with the nature of their color, which, in turn, is associated with a set of pigments, and is also based on general structural features. Some taxonomists distinguish red algae into a separate subkingdom in the plant kingdom, since red algae have a number of features that significantly distinguish them from other eukaryotic algae.
The department is divided into two classes: Bangiophyceae and Florideophyceae.
The class Bangiophyceae includes unicellular, colonial and multicellular forms. Main representatives: Porphyridium, Chrootece, Goniotrichum, Asterocytis, Porphyra.
The Floridea class (Florideophyceae) unites multicellular, complexly organized forms.
The spores and gametes of purple algae lack flagella, and their development cycle includes not two, like other algae, but three stages. After the fusion of gametes, a diploid organism develops from the zygote (in one or another, sometimes reduced, form) - a sporophyte that produces diploid spores. From these spores, the second diploid generation develops - the sporophyte, in the cells of which certain time Meiosis occurs and haploid spores are formed. From such a spore, the third generation develops - a haploid gametophyte that produces gametes.
Red algae have a complex development cycle not found in other algae. Reproductive cells of red algae never have flagella. They emerge from the sporangium or gametangium as a result of the formation large quantity mucus and are carried by water.
Bibliography
1. Botany: plant taxonomy. / Ed. M.I. Ashmarina. - Tomsk, 2004. - 248 p.
2. Garibova L.V. etc. Algae, lichens and bryophytes. - M.: Mysl, 1998. - P.40
3. Garibova L.V. and others. Course of lower plants. - M.: Higher School, 2001. - 162 p.
4. Raven P. et al. Modern botany. - M.: Mir, 2003. - 362 p.
5. A. G. Elenevsky, M. P. Solovyova, V. N. Tikhomirov. Botany. Systematics of higher, or terrestrial, plants. - M.: Academy, 2006.
6. Basov V.M., Efremova T.V. Anatomy, morphology and systematics of plants. - M.: 2004
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