This is a peculiar group of lower plants, which consist of two different organisms - a fungus (representatives of ascomycetes, basidiomycetes, phycomycetes) and algae (green - cystococcus, chlorococcus, chlorella, cladophora, palmella is found; blue-green - nostoc, gleocaps, chroococcus), forming a symbiotic cohabitation , characterized by special morphological types and special physiological and biochemical processes. Some lichens were thought to contain bacteria (Azotobacter). However, later studies did not confirm their presence in lichens.

Lichens differ from other plants in the following ways:

1. Symbiotic cohabitation of two different organisms - a heterotrophic fungus (mycobiont) and an autotrophic algae (phycobiont). Lichen cohabitation is constantly and historically determined, and not by chance, for a short time. In a real lichen, the fungus and algae come into close contact, the fungal component surrounds the algae and can even penetrate into its cells.
2. Specific morphological forms of external and internal structure.
3. The physiology of the fungus and algae in the lichen thallus differs in many ways from the physiology of free-living fungi and algae.
4. The biochemistry of lichens is specific: they form secondary metabolic products that are not found in other groups of organisms.
5. Reproduction method.
6. Attitude to environmental conditions.

Morphology. Lichens do not have a typical green color, they do not have a stem, leaves (this is how they differ from mosses), their body consists of a thallus. The color of lichens is grayish, greenish-gray, light or dark brown, less often yellow, orange, white, black. The color is due to pigments that are in the shells of the hyphae of the fungus, less often in the protoplasm. There are five groups of pigments: green, blue, purple, red, brown. The color of lichens may also depend on the color of lichen acids, which are deposited in the form of crystals or grains on the surface of the hyphae.

There are lichens scale, or cortical, leafy and bushy.

At scale thallus has the appearance of a powdery, tuberculate or smooth skin, which is tightly fused with the substrate; about 80% of all lichens belong to them. Depending on the substrate on which scale lichens grow, they are distinguished: epilithic, developing on the surface of rocks; epifleodnye - on the bark of trees and shrubs; epigeic - on the surface of the soil, epixial - on rotting wood.

The lichen thallus can develop inside the substrate (stone, tree bark). There are scale lichens with a spherical shape of the thallus (the so-called nomadic lichens).

At leaf lichens thallus has the appearance of scales or rather large plates that are attached to the substrate in several places with the help of bundles of fungal hyphae. The simplest thallus of leaf lichens has the form of one large rounded leaf-shaped plate, reaching a diameter of 10-20 cm. Such a thallus is called monophyllic. It is attached to the substrate in its central part with the help of a thick short leg called gomf. If the thallus consists of several leaf-shaped plates, it is called polyphilic. A characteristic feature of the leaf thallus of lichens is that its upper surface differs in structure and color from the lower one. Among leaf lichens, loose, nomadic forms are also found.

At fruticose lichens thallus consists of branched filaments or stems, grows together with the substrate only at the base; grow up, sideways, or hang down - "bearded" lichens. The thallus of fruticose lichens has the appearance of an upright or hanging bush, less often unbranched upright outgrowths. This is the highest stage in the development of the thallus. The height of the smallest is only a few millimeters, the largest - 30-50 cm (sometimes 7-8 m - a long usnea, hanging in the form of a beard from the branches of larch and cedar in taiga forests). Thalluses come with flat and rounded lobes. Sometimes large bushy lichens in tundra and high mountains develop additional attachment organs (hapters), with the help of which they grow to the leaves of sedges, grasses, and shrubs. In this way, lichens protect themselves from separation by strong winds and storms.

According to the anatomical structure, lichens are of two types.

• In one of them, the algae are scattered throughout the thickness of the thallus and are immersed in the mucus that the alga secretes (homeomeric type). This is the most primitive type. Such a structure is typical for those lichens whose phycobiont are blue-green algae - nostoc, gleokapsa, etc. They form a group of slimy lichens.
• In another (heteromeric type), several layers can be distinguished under a microscope on a cross section. Above is the upper bark, which looks like intertwined, tightly closed fungal hyphae. Under it, the hyphae lie more loosely, algae are located between them - this is the gonidial layer. Below, the fungal hyphae are located even more loosely, large gaps between them are filled with air - this is the core. The core is followed by the lower crust, which is similar in structure to the upper. Bundles of hyphae pass through the lower cortex from the core, which attach the lichen to the substrate.

Crustose lichens do not have a lower bark and the fungal hyphae of the hearts fuse directly with the substrate.

Bushy radially built lichens have a bark on the periphery of the transverse section, a gonidial layer under it, and a core inside. The bark performs protective and strengthening functions. Attachment organs usually form on the lower crustal layer of lichens. Sometimes they look like thin threads, consisting of one row of cells. They are called rhizoids. Rhizoids can join to form rhizoidal bands.

In some foliose lichens, the thallus is attached with a short stalk (gomfa) located in the central part of the thallus.

The algae zone performs the function of photosynthesis and accumulation of organic substances. The main function of the core is to conduct air to algae cells containing chlorophyll. In some bushy lichens, the core also performs a strengthening function.

The organs of gas exchange are pseudocyfellae (ruptures of the cortex, visible to the naked eye as irregularly shaped white spots). On the lower surface of leaf lichens there are round, regular white depressions - these are cyphella, also gas exchange organs. Gas exchange is also carried out through perforations (dead areas of the crustal layer), cracks and breaks in the crustal layer.

Nutrition

Hyphae play the role of roots: they absorb water and mineral salts dissolved in it. Algae cells form organic substances, perform the function of leaves. Lichens can absorb water with the entire surface of the body (they use rainwater, fog moisture). An important component in the nutrition of lichens is nitrogen. Those lichens that have green algae as a phycobiont receive nitrogen compounds from aqueous solutions when their thallus is saturated with water, partly directly from the substrate. Lichens that have blue-green algae (especially nostocs) as a phycobiont are able to fix atmospheric nitrogen.

reproduction

Lichens reproduce either by spores, which are formed by the mycobiont sexually or asexually, or vegetatively - by fragments of the thallus, soredia and isidia.

During sexual reproduction, sexual sporulation in the form of fruiting bodies is formed on the thalli of lichens. Among the fruit bodies in lichens, apothecia are distinguished (open fruit bodies in the form of disc-shaped formations); perithecia (closed fruiting bodies that look like a small jug with a hole at the top); gasterothecia (narrow fruiting bodies of an elongated shape). Most lichens (over 250 genera) form apothecia. In these fruiting bodies, spores develop inside bags (sac-like formations) or exogenous, on top of elongated club-shaped hyphae - basidia. The development and maturation of the fruiting body lasts 4-10 years, and then for a number of years the fruiting body is able to produce spores. A lot of spores are formed: for example, one apothecia can produce 124,000 spores. They don't all grow. For germination, conditions are needed, primarily certain temperature and humidity.

Asexual sporulation of lichens - conidia, pycnoconidins and stylospores that occur exogenously on the surface of conidiophores. Conidia are formed on conidiophores that develop directly on the surface of the thallus, and pycnoconidia and stylospores - in special receptacles - pycnidia.

Vegetative propagation is carried out by thallus bushes, as well as special vegetative formations - soredia (dust particles - microscopic glomeruli, consisting of one or more algae cells surrounded by fungal hyphae, form a fine-grained or powdery whitish, yellowish mass) and isidia (small, variously shaped outgrowths of the upper surface of the thallus , the same color as it, they look like warts, grains, club-shaped outgrowths, sometimes small leaves).

The role of lichens in nature and their economic importance

Lichens are the pioneers of vegetation. Settling in places where other plants cannot grow (for example, on rocks), after a while, partially dying, they form a small amount of humus, on which other plants can settle. Lichens are widely distributed in nature (they live on soil, rocks, trees, some in water, found on metal structures, bones, glass, skin and other substrates). Lichens destroy rocks by releasing lichen acid. This destructive action is completed by water and wind. Lichens are capable of accumulating radioactive substances.

Lichens play an important role in human economic activity: they serve as food for deer and some other domestic animals; certain types of lichens (lichen manna, gyrofora in Japan) are consumed by humans; alcohol is extracted from lichens (from Icelandic cetraria, some types of cladonia), paints (from some types of rochel, okhrolekhni); they are used in the perfume industry (plum evernia - oak "moss"), in medicine (Icelandic "moss" - for intestinal diseases, for respiratory diseases, lobaria - for lung diseases, peltiger - for rabies, parmelia - for epilepsy, etc. ); antibacterial substances are obtained from lichens (usnic acid is the most studied).

Lichens almost do not harm human economic activity. Only two poisonous species are known (they are rare in our country).

Lichens

Lichens are a peculiar group of living organisms that grow on all continents, including Antarctica. In nature, there are more than 26,000 species of them.

For a long time, lichens have been a mystery to researchers. However, until now they have not come to a consensus regarding their position in the systematics of living nature: some attribute them to the kingdom of plants, others to the kingdom of fungi.

The body of the lichen is represented by a thallus. It is very diverse in color, size, shape and structure. The thallus can have the shape of a body in the form of a crust, a leaf-shaped plate, tubules, a bush and a small rounded lump. Some lichens reach a length of more than a meter, but most have a thallus 3-7 cm in size. They grow slowly - they increase by a few millimeters in a year, and some by fractions of a millimeter. Their thallus is often hundreds or thousands of years old.

Lichens do not have the typical green color. The color of lichens is grayish, greenish-gray, light or dark brown, less often yellow, orange, white, black. The color is due to pigments that are in the shells of the hyphae of the fungus. There are five groups of pigments: green, blue, purple, red, brown. The color of lichens may also depend on the color of lichen acids, which are deposited in the form of crystals or grains on the surface of the hyphae.

Living and dead lichens, dust and sand grains accumulated on them create a thin layer of soil in the non-exposed soil, in which mosses and other terrestrial plants can gain a foothold. Growing, mosses and grasses shade ground lichens, cover them with dead parts of their bodies, and lichens eventually disappear from this place. Falling asleep does not threaten lichens of vertical surfaces - they grow and grow, absorbing moisture from rains, dews and fogs.

Depending on the external appearance of the thallus, lichens are divided into three types: scale, leafy and bushy.

Lichen types. Morphological features

Lichens are the first settlers on bare ground. On bare stones scorched by the sun, on sand, on logs and tree trunks.

In extremely harsh conditions, lichens grow on stones and rocks in Antarctica. Living organisms have to live here at very low temperatures, especially in winter, and with little or no water. Due to the low temperature, precipitation there always falls in the form of snow. Lichen cannot absorb water in this form. But the black color of the thallus rescues him. Due to high solar radiation, the dark surface of the lichen body quickly heats up even at low temperatures. The snow falling on the heated thallus melts. The lichen immediately absorbs the moisture that has appeared, providing itself with the water it needs for respiration and photosynthesis.

Structure

The thallus consists of two different organisms - a fungus and an algae. They interact so closely with each other that their symbiosis seems to be a single organism.

The thallus is a set of intertwined mushroom threads (hyphae).

Between them, in groups or singly, there are cells of green algae, and in some - of cyanobacteria. Interestingly, the species of fungi that make up a lichen do not exist in nature without algae at all, while most of the algae that make up the lichen thallus are found in a free-living state, separately from the fungus.

The lichen is fed by both symbionts. Fungal hyphae absorb water and minerals dissolved in it, and algae (or cyanobacteria), which contains chlorophyll, form organic substances (due to photosynthesis).

Hyphae play the role of roots: they absorb water and mineral salts dissolved in it. Algae cells form organic substances, perform the function of leaves. Lichens absorb water with the entire surface of the body (they use rainwater, fog moisture). An important component in the nutrition of lichens is nitrogen. Those lichens that have green algae as a phycobiont receive nitrogen compounds from aqueous solutions when their thallus is saturated with water, partly directly from the substrate. Lichens that have blue-green algae as a phycobiont (especially nostocs) are able to fix atmospheric nitrogen.

Internal structure

This is a peculiar group of lower plants, which consist of two different organisms - a fungus (representatives of ascomycetes, basidiomycetes, phycomycetes) and algae (green - cystococcus, chlorococcus, chlorella, cladophora, palmella is found; blue-green - nostoc, gleokapsa, chroococcus), forming symbiotic cohabitation, characterized by special morphological types and special physiological and biochemical processes.

According to the anatomical structure, lichens are of two types. In one of them, the algae are scattered throughout the thickness of the thallus and are immersed in the mucus that the alga secretes (homeomeric type). This is the most primitive type. Such a structure is typical for those lichens whose phycobiont is blue-green algae. They form a group of slimy lichens. In others (heteromeric type), several layers can be distinguished under a microscope on a cross section.

Above is the upper bark, which looks like intertwined, tightly closed fungal hyphae. Under it, the hyphae lie more loosely, algae are located between them - this is the gonidial layer. Below, the fungal hyphae are located even more loosely, large gaps between them are filled with air - this is the core. The core is followed by the lower crust, which is similar in structure to the upper. Bundles of hyphae pass through the lower cortex from the core, which attach the lichen to the substrate. Crustose lichens do not have a lower bark, and the fungal hyphae of the core grow together directly with the substrate.

Bushy radially built lichens have a bark on the periphery of the transverse section, a gonidial layer under it, and a core inside. The bark performs protective and strengthening functions. Attachment organs usually form on the lower crustal layer of lichens. Sometimes they look like thin threads, consisting of one row of cells. They are called rhizoids. Rhizoids can join to form rhizoidal bands.

In some foliose lichens, the thallus is attached with a short stalk (gomfa) located in the central part of the thallus.

The algae zone performs the function of photosynthesis and accumulation of organic substances. The main function of the core is to conduct air to algae cells containing chlorophyll. In some bushy lichens, the core also performs a strengthening function.

The organs of gas exchange are pseudocyphellae (ruptures of the cortex, visible to the naked eye as irregularly shaped white spots). On the lower surface of leaf lichens there are round, regular white depressions - these are cyphella, also gas exchange organs. Gas exchange is also carried out through perforations (dead areas of the crustal layer), cracks and breaks in the crustal layer.

reproduction

Lichens reproduce mainly by pieces of the thallus, as well as by special groups of fungal and algae cells, which are formed in large numbers inside its body. Under the pressure of their overgrown mass, the body of the lichen is torn, groups of cells are carried by wind and rain streams. In addition, fungi and algae have retained their own methods of reproduction. Mushrooms form spores, algae reproduce vegetatively.

Lichens reproduce either by spores that form a mycobiont sexually or asexually, or vegetatively - by fragments of the thallus, soredia and isidia.

During sexual reproduction, sexual sporulation in the form of fruiting bodies is formed on the thalli of lichens. Among the fruit bodies in lichens, apothecia are distinguished (open fruit bodies in the form of disc-shaped formations); perithecia (closed fruiting bodies that look like a small jug with a hole at the top); gasterothecia (narrow elongated fruiting bodies). Most lichens (over 250 genera) form apothecia. In these fruiting bodies, spores develop inside the bags (sac-like formations) or exogenously, on top of elongated club-shaped hyphae - basidium. The development and maturation of the fruiting body lasts 4-10 years, and then for a number of years the fruiting body is able to produce spores. A lot of spores are formed: for example, one apothecia can produce 124,000 spores. They don't all grow. For germination, conditions are needed, primarily certain temperature and humidity.

Asexual sporulation of lichens - conidia, pycnoconidia and stylospores that occur exogenously on the surface of conidiophores. Conidia are formed on conidiophores that develop directly on the surface of the thallus, and pycnoconidia and stylospores - in special receptacles - pycnidia.

Vegetative reproduction is carried out by thallus bushes, as well as special vegetative formations - soredia (dust particles - microscopic glomeruli, consisting of one or more algae cells surrounded by fungal hyphae, form a fine-grained or powdery whitish, yellowish mass) and isidia (small, variously shaped outgrowths of the upper surface of the thallus , the same color as it, they look like warts, grains, club-shaped outgrowths, sometimes small leaves).

Lichens are the pioneers of vegetation. Settling in places where other plants cannot grow (for example, on rocks), after a while, partially dying, they form a small amount of humus, on which other plants can settle. Lichens destroy rocks by releasing lichen acid. This destructive action is completed by water and wind. Lichens are capable of accumulating radioactive substances.

Lichens - structure, reproduction and feeding methods

Lichens are a very interesting and peculiar group of lower plants. Lichens (lat. Lichenes) - symbiotic associations of fungi (mycobiont) and microscopic green algae and / or cyanobacteria (photobiont, or phycobiont); the mycobiont forms a thallus (thallus), inside which the photobiont cells are located. The group includes from 17,000 to 26,000 species in about 400 genera. And every year, scientists discover and describe dozens and hundreds of new unknown species.

Fig.1. Lichen Cladonia stellate Cladonia stellaris

The lichen combines two organisms with opposite properties: an algae (usually green), which creates organic matter in the process of photosynthesis, and a fungus that consumes this substance.

As organisms, lichens were known to scientists and the people long before the discovery of their essence. Even the great Theophrastus (371 - 286 BC), "the father of botany", gave a description of two lichens - usnea (Usnea) and rocella (Rocce11a). The latter was already used to obtain dyes. The beginning of lichenology (the science of lichens) is considered to be 1803, when a student of Carl Linnaeus, Eric Acharius, published his work “Methodus, qua omnes detectos lichenes ad genera redigere tentavit” (“Methods by which everyone can identify lichens”). He identified them as an independent group and created a system based on the structure of the fruiting bodies, which included 906 species described at that time. The first to point out the symbiotic nature in 1866, using the example of one of the species, was the physician and mycologist Anton de Bari. In 1869, the botanist Simon Schwendener extended these ideas to all species. In the same year, Russian botanists Andrei Sergeevich Famintsyn and Osip Vasilievich Baranetsky discovered that the green cells in lichen are unicellular algae. These discoveries were perceived by contemporaries as "amazing".

Lichens are divided into three unequal groups:

1. It includes a greater number of lichens, a class of marsupial lichens, since they are formed by marsupial fungi

2. A small group, a class of basidial lichens, since they are formed by basidial fungi (less resistant fungi)

3. “Imperfect lichens” got their name due to the fact that fruiting bodies with spores were not found in them.

External and internal structure of lichens

The vegetative body of the lichen - thallus, or thallus, is very diverse in shape and color. Lichens are painted in a variety of colors: white, pink, bright yellow, orange, orange-red, gray, bluish-gray, grayish-green, yellowish-green, olive brown, brown, black and some others. The color of the lichen thallus depends on the presence of pigments that are deposited in the hyphae membranes, less often in the protoplasm. The hyphae of the crustal layer of lichens and various parts of their fruiting bodies are the richest in pigments. Lichens have five groups of pigments: green, blue, purple, red, brown. The mechanism of their formation has not yet been elucidated, but it is quite obvious that the most important factor influencing this process is light.

Sometimes the color of the thallus depends on the color of lichen acids, which are deposited in the form of crystals or grains on the surface of the hyphae. Most lichen acids are colorless, but some of them are colored, and sometimes very brightly - in yellow, orange, red and other colors. The color of the crystals of these substances determines the color of the entire thallus. And here the most important factor contributing to the formation of lichen substances is light. The brighter the lighting in the place where the lichen grows, the brighter it is colored. As a rule, lichens of the highlands and polar regions of the Arctic and Antarctic are very brightly colored. This is also related to lighting conditions. The high-mountain and polar regions of the globe are characterized by a high transparency of the atmosphere and a high intensity of direct solar radiation, providing here a significant brightness of illumination. Under such conditions, a large amount of pigments and lichen acids are concentrated in the outer layers of thalli, causing the bright color of lichens. It is believed that the colored outer layers protect the underlying algae cells from excessive light intensity.

Due to the low temperature, precipitation in Antarctica falls only in the form of snow. In this form, they cannot be used by plants. This is where the dark color of lichens comes to their aid.

Dark-colored thalli of Antarctic lichens, due to high solar radiation, quickly heat up to a positive temperature even at negative air temperatures. The snow falling on these heated thalli melts, turning into water, which the lichen immediately absorbs. Thus, it provides itself with the water necessary for the implementation of the processes of respiration and photosynthesis.

How diverse are the thalli of lichens in color, they are just as diverse in shape. The thallus may take the form of a crust, a leaf-shaped plate or a bush. Depending on the appearance, there are three main morphological types:

Scale. The thallus of scale lichens is a crust (“scale”), the lower surface is tightly fused with the substrate and does not separate without significant damage. This allows them to live on steep mountain slopes, trees, and even on concrete walls. Sometimes scale lichen develops inside the substrate and is completely invisible from the outside. As a rule, scale thalli are small in size, their diameter is only a few millimeters or centimeters, but sometimes it can reach 20–30 cm. rocks or tree trunks large spots, reaching a diameter of several tens of centimeters.

Leafy. Leafy lichens have the form of plates of various shapes and sizes. They are more or less tightly attached to the substrate with the help of outgrowths of the lower cortical layer. The simplest thallus of leafy lichens has the appearance of one large rounded leaf-shaped plate, reaching a diameter of 10–20 cm. Such a plate is often dense, leathery, painted in dark gray, dark brown or black.

bushy. According to the organizational level, fruticose lichens represent the highest stage in the development of the thallus. In fruticose lichens, the thallus forms many rounded or flat branches. Grow on the ground or hang from trees, wood debris, rocks. The thallus of fruticose lichens has the appearance of an upright or hanging bush, less often unbranched upright outgrowths. This allows fruticose lichens to take the best position by bending branches in different directions, in which algae can maximize the use of light for photosynthesis. Thallus of fruticose lichens can be of different sizes. The height of the smallest is only a few millimeters, and the largest is 30-50 cm. Hanging thalli of fruticose lichens can sometimes reach colossal sizes.

The internal structure of the lichen: crustal layer, gonidial layer, core, lower cortex, rhizoids. The body of lichens (thallus) is an interweaving of fungal hyphae, between which there is a population of photobiont.

Rice. 2. Anatomical structure of the lichen thallus

1 - heteromeric thallus (a - upper crustal layer, b - algae layer, c - core, d - lower crustal layer); 2 - homeomeric thallus of the slimy collema lichen (Collema flaccidum); 3 - homeomeric thallus of the slimy lichen leptogium (Leptogium saturninum) (a - crustal layer from the upper and lower sides of the thallus, b - rhizoids)

Each of the listed anatomical layers of the thallus performs a specific function in the life of a lichen and, depending on this, has a completely specific structure.

The crustal layer plays a very important role in the life of the lichen. It performs two functions at once: protective and strengthening. It protects the inner layers of the thallus from the effects of the external environment, especially algae from excessive lighting. Therefore, the crustal layer of lichens is usually dense in structure and is colored grayish, brown, olive, yellow, orange or reddish. The crust layer also serves to strengthen the thallus. The higher the thallus rises above the substrate, the more it needs to be strengthened. Strengthening mechanical functions in such cases are often performed by a thick crustal layer. Attachment organs usually form on the lower crustal layer of lichens. Sometimes they look like very thin threads, consisting of one row of cells. These threads are called rhizoids. Each such thread originates from one cell of the lower crustal layer. Often, several rhizoids are combined into thick rhizoidal strands.

In the zone of algae, the processes of assimilation of carbon dioxide and the accumulation of organic substances are carried out. As you know, for the implementation of photosynthesis processes, algae do not bypass sunlight. Therefore, the layer of algae is usually located near the upper surface of the thallus, directly under the upper crustal layer, and in vertically standing fruticose lichens, also above the lower crustal layer. The layer of algae is most often thin, and the algae are placed in it so that they are in almost the same lighting conditions. Algae in the lichen thallus can form a continuous layer, but sometimes mycobiont hyphae divide it into separate sections. To carry out the processes of carbon dioxide assimilation and respiration, algae also need normal gas exchange. Therefore, fungal hyphae in the zone of algae do not form dense plexuses, but are located loosely at some distance from each other.

Under the layer of algae is the core layer. Usually the core is much thicker than the crustal layer and the algae zone. The thickness of the thallus itself depends on the degree of development of the core. The main function of the core layer is to conduct air to algae cells containing chlorophyll. Therefore, most lichens are characterized by a loose arrangement of hyphae in the core. The air entering the thallus easily penetrates to the algae through the gaps between the hyphae. The core hyphae are weakly branched, with sparse transverse septa, with smooth, weakly gelatinous thick walls and a rather narrow lumen filled with protoplasm. In most lichens, the core is white, since the hyphae of the core layer are colorless.

According to the internal structure, lichens are divided into:

Homeomeric (Collema), photobiont cells are randomly distributed among fungal hyphae throughout the entire thickness of the thallus;

Heteromeric (Peltigera canina), thallus in cross section can be clearly divided into layers.

Lichens with heteromeric thallus are the majority. In the heteromeric thallus, the upper layer is cortical, composed of fungal hyphae. It protects the thallus from drying out and mechanical influences. The next layer from the surface is gonidial, or algal, in which the photobiont is located. In the center is the core, consisting of randomly intertwined hyphae of the fungus. Moisture is mainly stored in the core, it also plays the role of a skeleton. At the lower surface of the thallus there is often a lower bark, with the help of outgrowths of which (rhizine) the lichen is attached to the substrate. A complete set of layers is not found in all lichens.

As in the case of two-component lichens, the algal component - phycobiont - of three-component lichens is evenly distributed over the thallus, or forms a layer under the upper bark. Some three-component cyanolichens form specialized superficial or internal compact structures (cephalodia) in which the cyanobacterial component is concentrated.

Lichen feeding methods

Lichens are a complex object for physiological studies, since they consist of two physiologically opposite components - a heterotrophic fungus and an autotrophic algae. Therefore, it is first necessary to separately study the vital activity of the myco- and phycobiont, which is done with the help of cultures, and then the life of the lichen as an integral organism. It is clear that such a “triple physiology” is a difficult path of research, and it is not surprising that there is still a lot of mystery in the life of lichens. However, the general patterns of their metabolism are still elucidated.

Quite a lot of research is devoted to the process of photosynthesis in lichens. Since only a small part of their thallus (5 - 10% of the volume) is formed by algae, which nevertheless is the only source of supply of organic substances, a significant question arises about the intensity of photosynthesis in lichens.

Measurements have shown that the intensity of photosynthesis in lichens is much lower than in higher autotrophic plants.

For normal photosynthetic activity, the thallus must contain a certain amount of water, depending on the anatomical and morphological type of lichen. In general, in thick thalli, the optimal water content for active photosynthesis is lower than in thin and loose thalli. At the same time, it is very significant that many species of lichens, especially in dry habitats, are generally rarely or at least very irregularly supplied with an optimal amount of intrathallus water. After all, the regulation of the water regime in lichens occurs in a completely different way than in higher plants that have a special apparatus that can control the receipt and consumption of water. Lichens assimilate water (in the form of rain, snow, fog, dew, etc.) very quickly, but passively with the entire surface of their body and partly with the rhizoids of the underside. This absorption of water by the thallus is a simple physical process, such as the absorption of water by filter paper. Lichens are able to absorb water in very large quantities, usually up to 100 - 300% of the dry mass of the thallus, and some slimy lichens (kollems, leptogiums, etc.) even up to 800 - 3900%.

Lichens can be found almost everywhere, even in Antarctica. This group of living organisms has been a mystery to scientists for a long time, even now there is no consensus about their systematic position. Some believe that they should be attributed to the plant kingdom, while others - fungi. Next, we consider the types of lichens, the features of their structure, their significance in nature and for humans.

General characteristics of lichens

Lichens are the lowest group of organisms that consist of a fungus and algae that are in symbiosis with each other. The first are most often representatives of phycomycetes, ascomycetes or basidiomycetes, and the second organism is green or blue-green algae. Between these two representatives of the living world there is a mutually beneficial cohabitation.

Lichens, regardless of variety, do not have a green color, most often they can be gray, brown, yellow, orange or even black. It depends on the pigments and also on the color of the lichen acids.

Distinctive features of lichens

This interesting group of organisms is distinguished by the following features:

• The cohabitation of two organisms in a lichen is not accidental, it is due to historical development.
• Unlike plants or animals, this organism has a specific external and internal structure.
• The physiological processes occurring in the fungus and algae differ significantly from those in free-living organisms.
• Biochemical processes also have their own distinctive features: as a result of vital activity, secondary metabolic products are formed that are not characteristic of any group of living organisms.
• Special way of reproduction.
• Attitude to environmental factors.

All these features baffle scientists and do not allow to determine the permanent systematic position.

Lichen varieties

This group of organisms is often called the "pioneers" of land, since they can settle in completely lifeless places. There are three types of lichens:

1. Scale lichens. They got their name for the shape, similar to scale.
2. Leafy lichens. They look like one large leaf blade, hence the name.
3. fruticose lichens resemble a small bush.

Consider the features of each type in more detail.

Description of scale lichens

Almost 80% of all lichens are scale. In their form, they look like a crust or a thin film, firmly fused with the substrate. Depending on the habitat, scale lichens are divided into:

Due to their distinctive appearance, this group of lichens can be completely invisible and blend in with their surroundings. The structure of scale lichens is peculiar, so they are easy to distinguish from other species. But the internal structure is almost the same for everyone, but more on that later.

Territories of scale lichens

We have already considered why scale lichens got their name, but the question arises: are the habitats different? The answer can be given in the negative, because they can be found in almost every latitude. These organisms are amazingly able to adapt to absolutely any conditions.

Scale types of lichens are distributed throughout the planet. Depending on the substrate, one or another species predominates. For example, in the Arctic it is impossible to meet species that are common in the taiga, and vice versa. There is a binding to a certain type of soil: some lichens prefer clay, while others feel calm on bare rocks.

But among the wide variety of this group of organisms, you can find species that live almost everywhere.

Features of leafy lichens

The thallus of this species has the form of scales or plates of medium size, attached to the substrate with a bundle of fungal hyphae. The simplest thallus resembles a rounded leaf blade, which can reach a size of 10-20 cm in diameter. With this structure, the thallus is called monophilic. If there are several plates, then polyphilic.

A distinctive feature of this type of lichen is the difference in the structure and color of the lower and upper parts. There are nomadic forms.

"Bearded" lichens

This name was given to fruticose lichens for their thallus, consisting of branched filaments that grow together with the substrate and grow in different directions. The thallus resembles a hanging bush, there are also upright forms.

The sizes of the smallest representatives do not exceed a few millimeters, and the largest specimens reach 30-50 cm. In tundra conditions, lichens can develop attachment organs, with the help of which organisms protect themselves from separation from the substrate in strong winds.

The internal structure of lichens

Almost all types of lichens have the same internal structure. Anatomically, there are two types:

It should be noted that those lichens that belong to scale do not have a lower layer, and the hyphae of the core directly grow together with the substrate.

Nutritional features of lichens

In the process of nutrition, both organisms living in symbiosis take part. Fungal hyphae actively absorb water and minerals dissolved in it, and algae cells have chloroplasts, which means they synthesize organic substances as a result of photosynthesis.

We can say that hyphae play the role of the root system, extracting moisture, and algae act as leaves. Since for the most part lichens settle on lifeless substrates, they absorb moisture with their entire surface; not only rainwater, but also fog and dew are suitable for these purposes.

For normal growth and vital activity, lichens, like plants, need nitrogen. If green algae are present as a phycobiont, then nitrogen compounds are extracted from solutions when the thallus is saturated with moisture. It is easier for lichens, which have blue-green algae, they are able to extract nitrogen from the air.

Lichen reproduction

Regardless of the variety, all lichens reproduce in the following ways:

Considering that these organisms grow very slowly, we can conclude that the process of reproduction is also quite long.

Ecological role of lichens

The significance of this group of organisms on the planet is quite large. They are directly involved in the process of soil formation. They are the very first to settle in lifeless places and enrich them for the growth of other species.

Lichens do not require a special substrate for life, they can cover a barren area, preparing it for plant life. This is due to the fact that in the process of life, lichens secrete special acids that contribute to the weathering of rocks, oxygen enrichment.

Settling on bare rocks, they feel absolutely comfortable there, gradually creating favorable conditions for other species. Some small animals are able to change their color to match the color of lichens, thus disguise themselves and use them to protect themselves from predators.

The value of lichens in the biosphere

Currently, more than 26 thousand species of lichens are known. They are distributed almost everywhere, but it is surprising that they can serve as an indicator of the purity of the air.

These organisms are quite sensitive to pollution, therefore, in large cities near roads, lichen plants are practically not found. They simply do not survive there and die. It should be noted that scale lichens are the most resistant to poor environmental conditions.

Lichens are also directly involved in the circulation of substances in the biosphere. Since they belong to autoheterotrophic organisms, they easily accumulate the energy of sunlight and create organic substances. Participate in the process of decomposition of organic matter.

Together with bacteria, fungi and algae, lichens create favorable conditions for higher plants and animals. Settling on trees, these symbiotic organisms cause practically no harm, since they do not penetrate deep into living tissues. In some ways, they can even be called defenders, because a plant covered with lichens is less attacked by pathogenic fungi, lichen acids inhibit the growth of wood-destroying fungi.

But there is a downside: if the lichens grow too much and cover almost the entire tree, then they close the lentils, disrupting gas exchange. And for insect pests, this is a great refuge. For this reason, it is better to control the growth of lichens on fruit trees and clean the wood.

The role of lichens for humans

The question of the role of lichens in human life cannot be omitted. There are several areas where they are widely used:

Lichens do not cause any harm to human economic activity.

Summing up all that has been said, we can say that such nondescript and amazing organisms exist next to us. Despite their small size, their benefits are enormous, and for all living organisms, including humans.

Lichens are a peculiar group of perennial plant organisms, the body of which consists of two types of organisms - an autotrophic phycobiont and a heterotrophic mycobiont, forming a single symbiotic organism.

Lichens are complex organisms consisting of fungi and algae, forming, as it were, a new organism, with new morphological, physiological and ecological properties.

Phycobiont is an algae, mainly green algae and less often blue-green or yellow-green.

Most lichen algae are found in a free-living state, but some of their species are known only as part of lichens.

Green lichen algae are represented by the genera Trebonxia, ​​Parmella, Gleocystis, Coccomyces and other microscopic algae. Of the filamentous greens, species of the genera Trentepohlia and Cladophora are most widely distributed in lichens.

Of the blue-greens, Nostoc, Anabaena, Gleocapsa, Hyella, Chroococcus, Stigonema, Calothrix, Dichothrix are often found.

Of the yellow-green (variegated) algae, lichens most often include species from the genus Heterococcus.

In total, 28 species of algae are found in lichens, of which up to 90% are algae from the genera Trebonxia, ​​Nostoc, Trentepohlia.

Mycobiont is a fungus, most often represented by a species of marsupial fungi - pyrenomycetes or discomycetes. Only in some tropical and subtropical lichen species does the fungus belong to the basidiomycetes. A small group of lichens has imperfect fungi with non-cellular mycelium.

The fungi that make up lichens are completely in the air and have a number of features - the walls of the fungal cells are perforated, the cells are connected by cytoplasmic bridges. The hyphal sheaths are thickened and provide mechanical stability to the thallus. In many lichen-forming fungi, hyphae can become mucilaginous, which is not usually the case in free-living fungi. Lichen fungi have fat cells.

Lichens can almost always be distinguished from members of other plant groups.

They differ from algae not in their green color, in a different type of thallus, and in their habitat.

They are well distinguished from mushrooms by the appearance of the thallus and living not in the substrate, but on its surface.

From mosses, with which the higher representatives of lichens are often mixed, they differ in their non-green color and the lack of differentiation into stems and leaves.

Lichens can live where neither fungi nor algae are able to live on their own. At the same time, the fungus provides algae with water and mineral salts, and itself uses organic substances synthesized by algae, which is fully consistent with the symbiotic mode of existence.

As a rule, lichen symbionts are one type of fungus and one type of algae, but some lichens, in addition to one type of fungus, may include two types of algae - green and blue-green.

Lichen, being a symbiotic organism, differs from free-living fungi and algae in its morphological, anatomical, physiological, biochemical, ecological, and qualitative parameters.

The structure, life forms of lichens, arising from the interaction of fungi and algae, are not found separately. Their structure is the result of a long shaping process based on symbiosis. Lichens also produce special substances that are not found in other groups of organisms.

The vegetative body of lichens, called the thallus or thallus, like other lower plants, is not differentiated into leaves, stem and root.

The vegetative body of lichens consists entirely of intertwined fungal hyphae, between which algae are located.

In most lichens, dense plexuses of fungal filaments form the upper and lower cortical layers. Under the upper crustal layer is a layer of algae, where photosynthesis takes place and organic matter accumulates. Below is the core, consisting of loosely located hyphae and air cavities. The function of the core is to conduct air to the algae cells.

The color of the lichen thallus is due to the presence of various pigments and can be gray, gray, greenish, yellow, golden, orange, brown, almost black, light brown, etc.

The shape and size of lichens is different.

Their sizes vary from a few millimeters to several centimeters.

According to the shape of the body and the external structure of the lichen, there are three main morphological types of lichen thalli:

Scale (Graphis scripta), the body of the thallus adheres tightly to the substrate in the form of scales, crusts up to 5 mm thick, granular or dusty deposits. They are found on the bark of trees, on the surface of the soil, on the surface of stones and rocks. By releasing acidic substances, scale lichens cause the destruction of stones.

Leafy (Hypogimnia physodes), the thallus has a rounded shape, often with jagged edges (leaf-like). Their diameter is 10 - 20 mm. Attached to the substrate are bundles of fungal hyphae - rhizidia, covered with a cortical layer. Leafy lichens are characterized by layer differentiation.

Bushy (Cladonia alpestris, Cladonia stellaris), slevishche consists of simple or branched stems and plates, called podetia. They are the most organized lichens. Their thallus is an upright or hanging bush. Hanging (epiphytic) lichens are large in size. For example, a usnea that settles on tree branches in taiga forests can reach 7-8 meters in length.

Lichens are attached to the substrate by special outgrowths located on the underside of the thallus.

The internal structure of lichens is not the same. The most primitive are some scale lichens, in which algae cells are distributed evenly between the filaments of the fungus - hyphae.

The thalli of more highly organized lichens have several layers of cells, each of which performs a specific function.

Anatomically, two types of lichen thalli are distinguished:

The first type is homeomeric, in which the cells of the phycobiont (algae) are evenly distributed in the thickness of the thallus and the hyphae of the fungus are evenly distributed in the mucus secreted by them in all directions;

The second type of lichen thallus is heteromeric, characterized by some differentiation of the thallus. From above, the thallus is covered with an upper bark consisting of tightly woven hyphae of the fungus. Inside the thallus, the hyphae are located loosely and between them there are voids filled with air. These air layers receive carbon dioxide and oxygen necessary for respiration and photosynthesis. From below, the thallus is covered with a lower bark, through which the hyphae of the fungus pass, with the help of which the lichens are attached to the substrate.

The presence of the lower bark of the thallus is inherent in leafy and bushy lichens. Scale lichens do not have a thallus lower bark, because they grow together with the substrate core.

Lichens reproduce in three ways: sexually, asexually and vegetatively. Lichens reproduce by spores that form a fungus, or vegetatively - by breaking off pieces of thalli and then germinating in a new place. Fungal spores can be unicellular or multicellular. Once in favorable conditions, they form the primary mycelium. The further development of this mycelium and the formation of the thallus depend on whether the hyphae of the fungus meet the algae corresponding to this type of lichen. If there are no such algae on the substrate where the primary mycelium grows, the primary mycelium dies, and if there is, then the thallus begins to form.

In terms of chemical composition, lichens, like all other plants, consist of a large amount of proteins, fats, carbohydrates and mineral salts.

The most characteristic distinguishing feature of lichens is their high content of carbohydrates, chemically close to cellulose. Lichenin, isolichenin and evernin were found among polysaccharides.

Lichens are characterized by the presence of a very powerful enzyme apparatus. They have both endoenzymes (amylase, cellulase, lichenase, tannase, lipase, urease, catalase, chymase, peroxidase, asparaginase, oxidase, tyrosinase, phenolase) and exoenzymes (lipase, invertase, amylase, lichenase, tannase, urease, catalase). , zymase, asparaginase, phenolase), which provide lichens with biosynthesis processes and allow them to actively participate in the cycle of substances and be used in biotechnology.

The activity of lichen enzymes is significantly influenced by the geographic zone, substrate and habitat, temperature, radiation, time of day and year, degree of cleanliness of the environment, etc.

Lichen components provide the synthesis of lichen acids, which promote metabolic processes, protect against the harmful effects of solar radiation, and ensure the impermeability of the thallus. Lichen acids contribute to the penetration of oxygen, carbon dioxide and atmospheric nitrogen into the thallus.

The composition of lichens includes a group of substances that are similar in nature to tannins and tannins, but have a simpler structure. These substances are called lichen acids. They can be colorless or have a red, brown, yellow, violet, orange, black color; they are easily soluble in ether and insoluble in water. The color of lichens depends on the color range of lichen acids.

With their acids, lichens have a chemical and physical effect on the substrate.

Lichens are found in all botanical and geographical zones (in temperate and cold regions, in humid and temperate tropics)

Lichens are distributed throughout the globe - from polar cold rocks to hot desert stones. Lichens live in the Arctic and Antarctic, at the edge of eternal snow and in the mountains, in waterless deserts, i.e. where the most difficult conditions for life, due to the fact that they are able to stay in a dry, dehydrated state for a long time, suspending all vital functions until the first moistening. The humidity of the lichen thallus depends on the humidity of the environment. Dry lichens very quickly absorb moisture, the source of which can be rain, fog, dew, melting snow, atmospheric water vapor. It should also be noted here that along with water, lichens absorb various pollutants, and this, in turn, can cause the death of lichens.

The areas of distribution (ranges) of various lichens are different.

Their distribution is due to many factors, of which the main ones are the ability of lichens to withstand the adverse effects of the environment, the range and speed of the transfer of part of the plant used for reproduction, undemanding to the substrate, etc.

The harsh living conditions of lichens cause their slow growth. This is due to the relatively weak ability for photosynthesis, i.e. independent formation of organic substances due to solar energy.

The intensity of the process of photosynthesis (as a source of carbohydrates) in lichens depends on environmental conditions, which include environmental humidity, light, temperature, atmospheric pollution with various pollutants, the presence of nitrogen, mineral salts, etc.

The soil, as a source of nutrients, also plays a significant role in the process of lichen growth. The soil on which lichens grow in most cases is poor in organic matter necessary for nutrition.

Lichens grow slowly and develop slowly, and this was one of the reasons for the displacement of lichens into harsh habitats, but in these places lichens are not threatened by competition from stronger rivals.

In particular, many of them develop on tree trunks, on stones and rocks, on poorly fertile soils, in the tundra, on mountain tops, in pine forests, etc. Settling on barren soils, lichens gradually loosen it and enrich it with organic matter and contribute to the formation of a fertile soil layer.

Lichens grow slowly and develop slowly, but their life expectancy is very long (several tens of years).

Lichens are widely distributed in different ecological systems of the globe. They are an integral part of soil biocenoses, trunks and branches of trees, boulders, rocks and other substrates, where they form groups - synusia. The main condition for the settlement of lichens on a particular substrate is the long-term immobility of the substrate with certain chemical properties. The species composition of lichen synusia and their biomass are much less compared to the groups of flowering and other representatives of higher plants, but this does not in the least detract from their role in the processes of the circulation of substances that ensure the life of our planet.

In relation to substrates and environmental factors, several ecological groups of lichens are distinguished: growing on soil, trees, stones, wood, etc. growing on soil, trees, stones, wood, etc.

Ground (epigean) lichens are lichens that live in places that are not very suitable for higher plants due to a small amount of nutrients. Such places include sandy soils, tundra, semi-desert, peat bogs, forest tundra, as well as places with adverse climatic conditions.

Ground lichens include: Peltigera canina, P.erumpens, P.aphthosa, P.malacea, P.polytactyla, Cetraria islandica. Stereocaulon tomentosum, Cladonia rangiferina, C.sylvatica, C.alpestris, C.deformis, C.mitis, Ochrolechia androgyna, O.tartarea, O.frigida, Alectoria ochruleuca, Cetraria islandica, C.cucullata.

Among the ground lichens there are nomadic ones, in which there is practically no connection with the soil and they are carried from place to place by the wind, and there is also a group of lichens that are permanently attached to the soil.

Nomadic ground lichens include Aspicilia esculenta, Parmelia vagans, Parmelia ryssolea, Carnycularia steppae.

Attached to the soil are Ramalina polymorpha, R. strepsilis, Parmelia pulla. Baeomyces roseus, B.rufus live on clay soil.

The species of the genera Collema and Verrucaria settle on limestones.

On soils that are not suitable for the development of other plants (in the tundra, forest-tundra, in the desert), species of the genera Cladonia, Cladina settle and live. Alectria, Cetraria, Stereocaulon, Ochroleuchina.

Cetraria pinastri, Cladonia digitata, species of the genus Peinigera are found in the forest and light forests.

Epiphytic lichens inhabit trees and shrubs.

They are attached to the bark or surface of the leaves. Their thallus can develop not only on the bark, but also under the bark.

Representatives of epiphytic lichens are: Alectoria alivacea, Bacidia apiahica, Bryopogon implexum, B.chalybeiforme, Cattilaria bouteillei, Evernia prunastri, E.furfuracea, E.thamnodes, Graphys scripta, Lobaria pulmonaria, Parmelia sulcata, P.physodes, Physcia pulverulenta, Ph. hispida, Ph.stellaria, Ph.ciliata, Ramalina thrausta, R.farinacea, R.pollinaria, Usnea longissima, U.dasypoga, U.hirta, U.florida, Xanthoria parientina, as well as species of the genera Cladonia, Cetraria, Hypogymnia.

Episcal lichens develop on treated, bare and decaying wood.

Epiphilic lichens grow on the leaves and needles of evergreen trees.

Epilithic (rock or scale) lichens settle and live on stones and rocks. Among them: Cetraria nivalis, C.fahlunensis, Collema multifidum, Gyrophora hirsuta, Gasparrinia decipiens, Parmelia sulcata, P.omphalodes, P.centrifuga, Rhisocarpon geographycum, Umbilicaria pustulata, as well as species of the genera Biatora, Placopsis, Verrucaria, Lecanora, Physcia, Dermatocarpon, Sphaerophorus, Stereocaulon.

The amphibious (aquatic) lichens living in the aquatic environment, in the zone of splashes, tides, surfs, in places often flooded with water, include: Dermatocarpon miniatum, D.aquaticum, hydrthyria venosa, Lecidea albocoerrulescens, Rhizocarpon obscuratum, etc.

Mushrooms(Mycota). An ancient group of organisms that appeared in the Proterozoic era (about 1 billion years ago) from ancient unicellular aerobic eukaryotes. At present, the Kingdom of Mushrooms has about 100 thousand species.

Structure. Body - mycelium Most mushrooms are made up of branched filaments called hyphae; mycelium lower mushrooms devoid of partitions and represent, as it were, one highly branched giant multinucleated cell (non-segmented, non-septate mycelium). Mycelium higher mushrooms divided by transverse partitions (septa) into individual cells containing one or more nuclei (segmented, septate mycelium), and the septa have openings - pores, sometimes so large that nuclei pass through them along the entire hypha.

Reproduction. When the substrate is depleted, mucor passes to sexual reproduction according to the type gametangiogamy. The hyphae of different mycelia (usually one thread is marked with a "-" sign, considering it male, and the other with a "+" sign, considering it female) approach swollen ends - gametangia, which are separated from the mycelium by partitions, the membranes between them dissolve, and the cytoplasm and nuclei of different signs merge. A zygote with numerous diploid nuclei is formed, covered with a thick spiny membrane. After a dormant period, the nuclei undergo meiosis, the outer shell of the zygote bursts, and it grows into a short hypha, ending in a small sporangium. In it, as a result of meiotic division, "+" and "-" spores are formed, sexual spore spores. Vegetative "+" and "-" mycelia develop from these spores.

Meaning . Mucoraceae take part in the circulation of organic (especially nitrogen-containing) soil substances. They often cause food spoilage. Some cause lung disease in birds, affect the hearing organs and the human central nervous system, and cause dermatomycosis.

Class Ascomycetes. About 30,000 species of saprotrophic soil and mold fungi inhabiting bread, vegetables and other products (Fig. 83). This class includes penicillium, yeast, morels, lines, ergot. Mycelium haploid, septate, branching. Through the pores, the cytoplasm and nuclei can pass into neighboring cells. Asexual reproduction is carried out exogenously, with the help of conidium- spores (translated from the Greek "conidia" - fine dust), lacing off from special cells conidiophore. During sexual reproduction, bags are formed - asci in which haploid spores of sexual sporulation are formed. The class Ascomycetes is divided into two subclasses - the voice-marsupials and the fruit-marsupials. In the voice-marsupials, the asci are located openly, as, for example, in yeasts; in the fruit-marsupials, they are located in the fruit bodies of spherical, closed - cleistothecia, flask-shaped with a hole at the top - perithecia, saucer-shaped - apothecia.

Penicillus (kistevik). Refers to fruit-bearing. At first it looks like a white cobweb plaque, and then acquires a greenish or bluish tint. Conidiophores rise up from the mycelium, the ends of which form a brush. At the tip of each branch, a chain of rounded spores - conidia - is exogenously formed. For the shape of the conidiophores, penicilli are sometimes called "watering mold" - groups of conidia at the ends of conidiophores resemble streams of water flowing from a watering can. They are carried by air currents and give rise to a new mycelium. Sexual reproduction is rare. In this case, the gametangia merge and form cleistothecia, fruiting bodies containing asci (bags), in which, after the fusion of nuclei, the formation of zygotes and meiosis, haploid ascospores develop. The formation of fruiting bodies can be detected by the appearance of a lemon-yellow color appearing where the accumulation of fruiting bodies is observed.

Saprotrophic species of penicillium mineralize soil organic matter. Some species are used to prepare the antibiotic penicillin. In 1928, the English scientist and physician Alexander Fleming drew attention to the fact that around a penicillium colony that had grown on a Petri dish with a culture of staphylococcus, all staphylococcus cells near the penicillium died. Only in 1941-1942 in England and the USA on the basis of penicillum notatum industrial production of penicillin began. In 1942, employees of the Institute of Epidemiology and Microbiology (IEM) named after. N.F.Gamalei headed by Z.V.Ermolyeva launched the production of domestic penicillin based on penicillum chrysogenum. Also used in the food industry for the preparation of special types of cheese.

Yeast. They belong to the voice-marsupials, the bags lie openly on the mycelium. Unicellular fungi, the vegetative body of which consists of single oval cells with one nucleus. Yeasts are represented by a large number of species widely distributed in nature. Only in culture there are baker's yeast, represented by hundreds of races: wine, bakery, beer. Vines are found naturally on the surface of fruits. Different types of yeast can exist in diploid or haploid phases.

Yeasts are characterized by a strongly pronounced aerobic metabolism. They use various sugars, simple and polyhydric alcohols, organic acids and other substances as a carbon source. The ability to ferment carbohydrates, breaking down glucose to form ethyl alcohol and carbon dioxide, served as the basis for the introduction of yeast into culture.

C 6 H 12 O 6 → 2C 2 H 5 OH + 2CO 2

Under favorable conditions (the presence of carbohydrates in the environment and the desired temperature), yeast reproduces vegetatively for a long time - by budding. The kidney arises at one end of the cell, begins to grow and separates from the mother cell. Often the daughter cell does not lose its connection with the mother cell and begins to form buds on its own. As a result, short chains of cells are formed. However, the connection between them is fragile, and when shaken, such chains break up into separate cells. With a lack of nutrition and an excess of oxygen, sexual reproduction occurs according to the type of chologamy - two cells merge, after the fusion of the nuclei, the diploid parent cell meiotically divides and a bag with 4 ascospores is formed. The spores fuse to form a new diploid yeast cell. Haploid yeasts have different life cycles, but sexual reproduction always results in the formation of sexual spores.

Yeast is used in baking, brewing, and winemaking. Yeast contains up to 50% protein, fats, carbohydrates, synthesize vitamins in large quantities (especially B 2). Therefore, they have valuable food and feed properties. Brewer's yeast is used in the treatment of anemia. Feed yeast is used to produce feed proteins.

A distinctive feature of basidiomycetes - the presence in each cell of the mycelium of two haploid nuclei. Such a cell is called dikaryonic, and the mycelium developing from it is called dikaryonic.

Most basidiomycetes are characterized by the formation of fruiting bodies. They are hoof-shaped outgrowths, but most often consist of a cap and a foot. They are called mushrooms in everyday life. As a rule, the cap is covered with colored hyphae that form the skin. The function of the fruiting bodies is the formation of spores. On the underside of the cap is a spore-forming layer, hymenophore, on which special structures are formed - basidia. Mature basidia resemble an inflated glove with 4 fingers. In young basidia, the haploid nuclei merge and a diploid nucleus is formed, which soon divides by meiosis, resulting in the formation of 4 nuclei that migrate to the terminal outgrowths of the basidium. When the basidiospores mature, the pressure inside the basidium rises and the basidiospores “shoot off” and spread with the help of air currents.

To increase the surface of sporulation (hymenophore), the lower part of the cap can be lamellar - it has the form of plates, radially diverging from the central lower surface of the cap in the form of rays (russula, chanterelle, mushroom, champignon) or tubular - it has the form of tubes that fit tightly to each other (boletus, boletus, butterdish, boletus).

Edible and poisonous mushrooms. About 200 forms of mushrooms are edible. The most famous white mushroom, boletus, boletus, oiler, champignon, oyster mushroom, camelina, milk mushroom and others. Among the inedible mushrooms, there are also poisonous ones. The most dangerous pale grebe, red fly agaric, smelly fly agaric.

R reproduction of mushrooms. The edges of the plates or the inner surface of the tubes are represented by a layer of basidia. In the basidia, the dikaryon phase of the development of basidiomycetes is completed. The dikaryon nuclei fuse to form a diploid nucleus. It meiotically divides, and the haploid nuclei pass into basidiospores, which form on the surface of the basidium.

Basidiospores - spores of sexual reproduction- germinate into the primary mononuclear mycelium.

But for the formation of fruiting bodies, it is necessary that two primary mycelia meet (somatogamy) and cells with two nuclei are formed. Moreover, only the protoplasts of the cells merge, and the nuclei form pairs - dikaryons, which begin to divide synchronously. As a result, a secondary dikaryonic mycelium is formed (Fig. 85).

Ergot belongs to the class Ascomycetes. It is easily detected in autumn: black-violet horns are clearly visible on the ears among the grains - sclerotia protruding from the ear.

They consist of densely intertwined hyphae. This is the dormant stage of the fungus. During the ripening period of rye, they fall to the ground and winter under the snow. In the spring, spherical heads of a reddish color on long legs are formed on them. On the periphery of the head there are many fruiting bodies - perithecia, resembling jugs, here are bags, asci with ascospores. Spore maturation occurs during the flowering of rye.

Mature spores fall on the stigma of the rye pistil and germinate, forming a mycelium. The hyphae of the mycelium penetrate into the ovary and destroy it. At the ends of the fungal threads, rounded conidiospores are formed in large numbers. At the same time, the threads of the fungus secrete a sweet liquid - honeydew, which attracts insects, primarily flies. Flying from one ear to another, insects spread fungal spores to uninfected ears. Conidia, having fallen on the ovary, form a mycelium, which thickens by autumn, its outer layers are colored, and instead of a caryopsis, horns form in the ear.

Rice. 87. Tinder fungus.

Ergot horns contain poisonous alkaloids that, when ingested, cause poisoning (sometimes fatal), called ergotism. Ergot alkaloids cause severe convulsions "evil writhing" spasms of blood vessels so strong that tissues die off, and gangrene begins - "Anton's fire". One of the ergot alkaloids is a close chemical analogue of the drug LSD, a powerful hallucinogen. Some of the ergot alkaloids are used medicinally.

Mushrooms-tinder. They belong to basidiomycetes. The hymenophore is tubular, growing from below every year. Tinder fungus infects many hardwoods. A spore of a tinder fungus, hitting a wound in a tree, germinates into a mycelium and destroys the wood.

After a few years, perennial hoof-shaped fruiting bodies are formed. Tinder fungi secrete enzymes that break down wood and turn it into dust. Even after the death of a tree, the fungus continues to live on a dead substrate (as a saprotroph), producing a large number of spores annually and infecting healthy trees. Therefore, dead trees and fruiting bodies of tinder fungi are recommended to be removed from the forest.

Their role in human economic activity is also important. They are used in the baking, brewing, dairy and wine industries for the production of wine, alcohol, beer, kvass, kefir. Hat mushrooms are of nutritional importance, as they contain a large amount of proteins, fats, carbohydrates, vitamins, valuable salts and aromatic substances. They are used to obtain antibiotics (penicillin), gibberellin - a growth substance, preparations for the destruction of harmful insects. Yeast is used as a medicinal product, as it is rich in vitamins.

Department Lichens (Lichenes). Includes about 20,000 species. Lichens are symbiotic organisms, which include mycobionts- fungi (more often ascomycetes, less often - basidiomycetes) and phycobionts- photoautotrophic organisms: algae (green) or cyanobacteria. Mycobionts provide the phototrophic component with water and mineral salts, create a microclimate for normal existence, and the phycobiont synthesizes organic substances not only for itself, but also for the fungus. Such a close relationship arises between symbionts that, as a result, a morphologically and physiologically integral organism is formed. Such coexistence of the fungus and algae is constant, but not entirely equal - the fungus plays the leading role in the symbiosis.

In low-organized lichens, some fungal hyphae penetrate the algae and use their contents; in highly organized hyphae, they form special structures that do not penetrate, but are tightly pressed against the algae cell membrane and absorbing the necessary substances do not interfere so much with the vital activity of the phycobiont.

Structure. The body of a lichen thallus (thallus), not differentiated into organs. The basis of the thallus is the interweaving of hyphae of the fungus, among which are algae. There are two main types of lichen thallus structure - homeomeric And heteromeric thallus. In a homeomeric lichen, algae cells are more or less evenly distributed throughout the thickness of the thallus, in heteromeric the hyphae of the fungus on the upper and lower sides form a dense plexus - the upper and lower cortical layer, between which there is a core of loosely located hyphae and a layer of algae.

Distinguished by shape scale, leafy and bushy lichens. Scale lichens are located on the surface of the substrate in the form of scale, crust. The substrate for them is the bark of trees and shrubs, various rocks. By releasing lichen acids, they destroy the rock surface, preparing the ground for the colonization of this surface by foliose and fruticose lichens, mosses and then flowering plants. They are pioneers of plant communities.

Leafy lichens have a body in the form of leaf-shaped plates attached to the soil or trees with hyphae bundles (parmelia, xanthoria). Bushy lichens look like more or less branched bushes, up to 12-15 cm high. The most famous of the bushy lichens are reindeer moss, or reindeer moss and sleeping. Three species from the genus cladonia are called yagel - forest cladonia, alpine cladonia, deer cladonia. Usnea, the bearded lichen, has a thallus in the form of a beard, thin threads of which, several tens of centimeters long, hang from the trees.

Lichens are able to absorb water both from the substrate and from the air with their entire thallus, are photophilous, undemanding to the substrate. Most lichens do not withstand even the slightest air pollution, they can be used for a general assessment of the degree of environmental pollution. This is the basis of one of the areas of indicator ecology - lichen indication.

Lichens grow extremely slowly, especially scale ones - up to 1 mm per year. The growth per year for leafy ones is 1-8 mm, for bushy ones - 1-35 mm.

reproduction lichens both sexually and asexually. Sexual reproduction is carried out due to the fungal component, which forms fruiting bodies (for example, apothecia, perithecia), in which bags with spores are formed. Germinating spores must meet the corresponding algae, only in this case a new lichen will form.

Algae cells can only reproduce vegetatively. Basically, lichens reproduce asexually, parts of the thallus or special formations - soredia or isidia.

Soredia- special formations, consisting of fungal hyphae, braiding algae cells (Fig. 90). They are formed inside the thallus and are released as a result of rupture of the cortical layer. Isidia- outgrowths of the thallus that form on the surface of the lichen and contain a group of algae under the cortical layer.

Lichens can exist in the most unfavorable conditions. They settle in the most barren places where other organisms are not able to exist.

Since lichens are very unpretentious, they are found on rocks among eternal ice and snow in the highlands, in the interior of Antarctica, on lifeless Arctic islands, in barren deserts, on completely bare volcanic formations. However, they also thrive in the rainforest.

The meaning of lichens. Being the first settlers of uninhabited spaces, lichens play a significant role in the soil-forming process, gradually destroying rocks and preparing the conditions for the settlement of this territory by higher plants. In vast areas of the Arctic, lichens are the main food for reindeer (moss reindeer).

Lichens play an important role in human life. Due to the presence of lichen acids, many of them have a pronounced bactericidal effect. In perfumery, lichens are used as perfume fixatives to produce litmus. There are lichens (lichen manna) that can be used as food.

Key terms and concepts

1. Mycelium. 2. Hyphae. 3. Septa. 4. Lower mushrooms. 5. Mukor. 6. Higher mushrooms. 7. Penicillium. 8. Conidia. 9. Gametangia. 10. Asci. 11. Basidia. 12. Yeast. 13. Smut. 14. Ergot. 15. Mycobionts of lichens. 16. Phycobionts of lichens. 17. Soredia. 18. Isidia.

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