Lichens are consumers of organic matter. Nutrition of lichens. What are lichens. See what “Lichen nutrition methods” are in other dictionaries. What does lichen look like?
Lichens are organisms whose body is formed as a result of a symbiosis of fungus and algae. The body of the lichen is called the thallus (thallus). The photosynthetic component of lichen is algae or cyanobacteria, and the fungus provides absorption of water and mineral salts.
Among algae, green and yellow-green algae are found most often, about 100 species in total. In the modern flora, there are about 13,500 species of lichens.
Lichens are found in various habitats from the North to the South Pole. They grow on stones and rocks, tree bark and plant leaves, soil, artificial substrates. Some lichens live in water.
According to the shape of the thallus, lichens are divided into three types: scale, leafy and bushy. Limescales have the appearance of crusts and are tightly fused with the substrate. Leafy have a flattened shape, parts of the thallus rise above the substrate and resemble leaves. They attach to the substrate with hyphal beams and can be separated without damaging the thallus from the substrate. Bushy lichens have the appearance of hanging or erect bushes, which are attached to the substrate only with the base of the thallus.
According to the internal structure, lichens are of two types. In some, algae are evenly distributed among fungal hyphae throughout the thickness of the thallus. The space between hyphae and algae is filled with mucus. This is a homeomeric type of structure. In other lichens, the dense interweaving of hyphae forms the upper cortex, under which
lies a layer of loosely located hyphae with algae cells between them. Loosely located hyphae that form the core are located under this layer. The core is underlain by the lower crust formed by closely woven hyphae. Bundles of hyphae emerge from the core, with the help of which the lichen is attached to the substrate.
Most often, lichens reproduce vegetatively: in parts of thallus; algae cells braided by fungal hyphae; specialized thallus outgrowths containing phyco- and mycobionts. After separation of these structures under favorable conditions, they begin to develop into a new lichen thallus. Lichens can breed both asexually and sexually, but this reproduction is associated with mycobiont. Lichens grow very slowly: over a year, their thallus grows from a few hundredths of a millimeter to several centimeters.
Lichens are able to accumulate solar energy and create organic compounds from inorganic ones. On the other hand, the lichen mycobiont is a heterotroph. Lichens are pioneers of vegetation, they are the first to master lifeless substrates, making them suitable for other organisms over time. Lichens are indicators of air pollution, especially sensitive to the sulfur dioxide content in the atmosphere. They are used in archeology and geomorphology to establish the age of the substrate.
Lichens serve as food for animals, especially in winter in the northern regions (for example, reindeer moss, or deer moss). Birds can use lichen thallus as a building material for their nests.
Some lichens are edible for humans. From lichens, a number of substances are used that are used in the perfume industry. Some lichens are used in traditional medicine in the treatment of a number of diseases.
Choose one correct answer.
1. Mushrooms are
1) a separate group of plants
2) symbiosis of plants and bacteria
3) a special group of animals
4) a special group of living things
2. Lower plants include
1) mushrooms 3) mosses
2) algae 4) lichens
3. A sign common to mushrooms and animals is *
1) lack of plastids
2) reproduction method
3) the presence of an internal skeleton
4) osmotrophic type of nutrition
| 4. | The fungal cell wall contains | ||
| 1) murein | 3) | cellulose | |
| 2) pectin | 4) | chitin | |
| 5. | Fungal mycelium formed | ||
| 1) chitin fibers | 3) | disputes | |
| 2) gifs | 4) | rhizoids | |
| 6. | Budding propagates | ||
| 1) mucor | 3) | penicillium | |
| 2) smut | 4) | yeast | |
| 7. | Lamellar mushrooms include | ||
1) russula
2) oil
3) mosses
4) boletus
8. Mycorrhiza is
1) rye fungal disease
2) symbiosis of the fungus with the roots of higher plants
3) the organ of reproduction of molds
4) one of the most poisonous mushrooms
9. Mycorrhiza forms
1) mucor 3) boletus
2) champignon 4) ergot
10. Mycelium is represented by one cell in
1) smut 3) penicilla
2) tinder fungus 4) flour
11. Mucor spores mature
1) in special balls at the ends of vertical hyphae
2) throughout the mycelium
3) in racemose branches
1) water and organic matter
2) water and minerals
3) exclusively with water
4) oxygen and carbon dioxide
Choose three correct answers.
16. A sign common to fungi and plants is
1) immobility
2) the presence of hard cell walls
3) continuous growth
4) storage of carbohydrates in the form of glycogen
5) the presence of mycelium
Lichens receive organic matter through photosynthesis. It is carried out at a temperature optimum of +10 to +25 o. The maximum productivity is observed at illumination from 4000 to 25000 lux. Epigeneous withstand up to 40 thousand lux; below 4 thousand - lepraria, condellaria. Lichens can carry out photosynthesis processes both at +35 о, and at -10 о. High temperature stops photosynthesis, if + high humidity is fatal, it loses its latency, parts of the thallus die off. For normal photosynthetic activity, a sufficient amount of water (65-90%) should be contained in the thallus of the lichen. Organic substances synthesized in the thallus by the photobiont are actively used by the photobiont. During photosynthesis, glucose is formed in the cells of the photobiont. It is absorbed by hyphae and turns into polyhydric alcohols (erythritol, valine, beckons, if there are cyanobacteria in the thallus)
An important component of lichen nutrition is nitrogen (especially if there is blue-green algae). Lichens obtain a certain part of nitrogen compounds from the substrate on which they grow, from rain in the form of mortar compounds, nitrophilic lichens on the rocks of bird bazaars - their droppings, from exhaust gases in the form of oxides. Most of the nitrogen is used by the mycobiont, the smaller part is the photobiont.
Lichens are not capable of regulating the water balance, since they do not have real roots for active absorption of water and protection against evaporation. The surface of the lichen can hold water for a short time in the form of liquid or steam. In dry conditions, water is quickly lost to maintain metabolism and the lichen goes into a photosynthetically inactive state, in which water can make up 2-15% of the mass. Unlike mycobiont, photobiont cannot be long without water. Trehalose sugar plays an important role in protecting vital macromolecules such as enzymes, membrane elements, and DNA. But lichens have found ways to prevent total loss of moisture. In many species, a thickening of the bark is observed to provide less water loss; thallus impairment (water absorption 100-3900%). Fast return of water with high insolation. The ability to maintain water in a liquid state is very important in cold areas, because frozen water is not suitable for use by the body.
The rhythm of life described above is one of the reasons for the very slow growth of most lichens. Sometimes lichens grow by only a few tenths of a millimeter per year, mostly less than one centimeter. Another reason for the slow growth is that the photobiont, often making up less than 10% of the lichen volume, takes on the provision of nutrients to the mycobiont. In good conditions, with optimal humidity and temperature, for example in foggy or rainy rainforests, lichens grow by several centimeters per year. The growth zone of lichens in scale form is located on the edge of the lichen, in leafy and bushy - at each apex.
8. The chemical composition of lichens.
Primary substances - those substances that are directly involved in cellular metabolism and the body of the lichen is built from them (shells of fungal hyphae, carbohydrates often contain chitin, hyphae contain lichine and its isomer (isoquinine), sucrose, trigalose, umbilicin, polysaccharide, erythrin, beckon, contain pectin substances, enzymes: emilase, catalose, lichenase; nitrogen-containing substances-amino acids: alanine, astoraginic acid, lysine, valine, tryptadine, tryptophan; mycobiont produces vitamins, radioactive: cesium and strontium, and other heavy metals; in Umb ilicaria accumulate various substances (zinc, cadmium, tin, lead).
Secondary connections.Available in large quantities, about 3000. Almost 80 compounds are specific: atranorin, gyrophoric acid, salocinic and usnic acid. Most have antibacterial, antitumor properties: drugs: evozin (a mixture of evernic and usnic acid) is used against streptococci, with mastitis; paramycin (evozin 2), (composed of: atramarine, isodic, caperate and usnic acid) in the treatment of open tuberculosis in humans; sodium salt of usnic acid (bina) is active against streptococci, pneumococci, tubercle bacillus; It is used in surgery for the treatment of suppuration of wounds, during plastic surgeries, burns of the 2-3 degree, in gynecology.
Most intracellular products, both photo- (phyco) and mycobionts, are not specific to lichens. Unique substances (extracellular), the so-called lichen, are formed exclusively by the mycobiont and accumulate in its hyphae. Today, more than 600 such substances are known, for example, usnic acid, mevalonic acid. Often, it is these substances that are decisive in the formation of the color of the lichen. Lichenic acids play an important role in weathering, destroying the substrate.
Lichens represent a complex object for physiological studies, since they consist of two physiologically opposing components - a heterotrophic fungus and an autotrophic algae. Therefore, it is first necessary to separately study the vital activity of the mycobacterium and phycobiont, which is done with the help of crops, and then the life of the lichen as a whole organism. It is clear that such a “triple physiology” is a difficult way to study, and it is not surprising that there is still a lot of mystery in the life of lichens. However, the general laws of their metabolism are still clarified.
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 matter, a significant question arises about the intensity of photosynthesis in lichens.
As measurements have shown, the intensity of photosynthesis in lichens is much lower than in higher autotrophic plants.
For normal photosynthetic activity, the thallus should contain a certain amount of water, depending on the anatomomorphological 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, the fact that many species of lichens, especially in dry habitats, is rarely or at least very irregularly supplied with the optimal amount of intravascular water is very significant. Indeed, 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 production and consumption of water. Lichens absorb 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 lower side. Such absorption by the thallus of water is a simple physical process, such as, for example, 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 mucous lichens (colemes, leptogiums, etc.) even up to 800 - 3900%.
The minimum water content in lichens in natural conditions is approximately 2-15% of the dry mass of the thallus.
Water thallus returns also quite quickly. Water-saturated lichens in the sun after 30-60 minutes lose all their water and become brittle, that is, the water content in the thallus becomes lower than the minimum required for active photosynthesis. From this follows the peculiar "arrhythmicity" of lichen photosynthesis - its productivity changes during the day, season, and a number of years depending on general environmental conditions, especially hydrological and temperature.
There are observations that many lichens are more active in photosynthesizing in the morning and evening hours, and that photosynthesis continues in the winter as well, and in ground forms even under thin snow cover.
An important component in the diet of lichens is nitrogen. Those lichens that have green algae as their phycobiont (and most of them) perceive nitrogen compounds from aqueous solutions when their thalli are saturated with water. It is possible that lichens also take part of nitrogen compounds directly from the substrate — soil, tree bark, etc. An ecologically interesting group is made up of the so-called nitrophilic lichens that grow in habitats rich in nitrogen compounds — on “bird stones” where there is a lot of bird excrement , on tree trunks, etc. (species of xanthoria, fiscia, kaloplaka, etc.). Lichens with blue-green algae (especially nostoks) as a phycobiont are able to fix atmospheric nitrogen, since the algae contained in them have this ability. In experiments with such species (from the genera Collem, Leptogium, Peltiger, Lobaria, Stick, etc.), it was found that their thalli quickly and actively absorb atmospheric nitrogen. These lichens often settle on substrates that are very poor in nitrogenous compounds. Most of the nitrogen fixed by the algae is sent to the mycobiont and only a small part is used by the phycobiont itself. There is evidence that the mycobiont in the lichen thallus actively controls the development and distribution of nitrogenous compounds fixed from the atmosphere by the phycobiont.
The rhythm of life described above is one of the reasons for the very slow growth of most lichens. Sometimes lichens grow by only a few tenths of a millimeter per year, mostly less than one centimeter. Another reason for the slow growth is that the photobiont, often making up less than 10% of the lichen volume, takes on the provision of nutrients to the mycobiont. In good conditions, with optimal humidity and temperature, for example in foggy or rainy rainforests, lichens grow by several centimeters per year.
The growth zone of lichens in scale form is located along the edge of the lichen, in leafy and bushy at each apex.
Lichens are one of the longest-living organisms and can reach the age of several hundred years, and in some cases more than 4,500 years, such as Rhizocagron geographicum, living in Greenland.
Lichens are a group of living organisms.
Their body is folded using a combination of two microorganisms, which are in a symbiotic relationship: a fungus (mycobiont) and algae (phycobiont or cyanobacteria).
general characteristics
The study of this species is the science of lichenology, which is a department of botany.
For a long time, lichens have been a mystery to scientists, although their use was widespread throughout various branches of human life. And only in 1867 the structure of this species was scientifically proven. Scientists-lichenologists were engaged in this.
At the moment, scientists have discovered more than 25 thousand species, but they all have a similar external and internal structure. The characteristics by which each species should be distinguished are based on structural features.
What does lichen look like?
As already mentioned, the main part of the species is the body, characterized by a variety of shapes and colors. In this case, growth can be a plate, a crust that looks like a leaf, in the form of a bush, tube or ball.
The height of the plant also varies in a fairly wide range: starting from 3 centimeters and ending with the height of human growth.
Types and names of lichens
Lichenology divided lichens into several groups in connection with the shape of the thallus:
In addition, based on the place where they grow, there are:
- epigeneous (mainly on a land basis);
- epiphytic (on a wood basis);
- epilithic (on stone).
Features of the internal structure
It is possible to see the structure of the lichen under a magnifying device. Lichen is an organism consisting of a part of the fungus - mycelium and algae intertwined.
Depending on how the cells of algae and fungi are distributed among themselves, another classification is distinguished:
- homeomeric, in which the phycobiont is located randomly among mycobiont cells;
- heteromeric, in which there is an explicit division into layers.
Lichens with a layered structure are found everywhere and have the following layer structure:
- The cortical layer is composed of mycobiont cells and protects against external influences, especially from drying out.
- Superficial or gonidial: contains exclusively phycobiont cells.
- The core consists of a fungus, acts as a skeleton, and also helps retain water.
- The lower crust performs the function of attaching to the base.
It is worth noting: in some species, any types of layers may be absent or have a modified structure.
Where do they live
Lichens are distinguished by the ability to adapt to absolutely any conditions of existence. For example, they grow on bare stones, rocks, walls and roofs of buildings, tree bark, etc.
This is due to the mutually beneficial cooperation of the mycobacteria and phycobionts. The vital activity of one complements the existence of the other, and vice versa.
How lichens eat
The implementation of nutrition is due to symbiotes. Since fungi do not have the function of autotrophic nutrition, in which the process of converting organic components from inorganic occurs, algae supply the body with the necessary elements.
This happens through photosynthesis. And the mushroom supplies the lichen with mineral salts, which it absorbs from the incoming liquid. In this way, the process of symbiosis occurs.
How to breed
Propagate in two ways:
- Sexual - is carried out due to spore formation.
- Vegetative - for this there are sorehii (an algal cell braided by a string of mycelium, which is carried by the wind) and isidia (outgrowths that form the surface layer of the thallus).
The value of lichens in nature and human life
They have the following positive effects:
Lichens are famous for their lifespan, because only a period of growth can reach 4 thousand years.
As a result of this, one can approximately determine the age of the rock from them.
Their use as fertilizer in the agricultural industry is popular. In addition, their use began in ancient times. Lichens were used as natural dyes.
Lichens are a unique species that carries a lot of useful properties and qualities that are applicable in virtually any branch of human life.
Currently described about 26 thousand species of lichens, in reality, their number can reach 40 thousand. It is believed that they were the first organisms that began to populate the land. Initially, it was they who formed the soil on earth.
Lichens are a rather complicated subject for research. These ancient organisms that appeared, according to scientists, more than 400,000,000 years ago, are incredibly interesting to study.
In contact with
The complexity of lichen research is that it cannot even be defined as a separate organism. Lichen is a symbiosis - a composite organism of two organisms: fungus and algae. Lichens have special biological properties that are not inherent in other organisms. A kind of metabolism, the formation of specific lichen substances, in the synthesis of which both components of the lichen participate, methods of reproduction and so on.
Separately existing, the alga does not possess the properties that it acquires by entering into symbiosis with the fungus. The reasons for the emergence of permanent algae-fungal organisms by scientists are not yet clear. Possible reasons are called “hunger” of the fungus, that is, conditions of lack of nutrients, as a result of which the mushrooms found a partner in the face of algae, which provide them with the necessary organic substances. Also, the cause of the combination of the fungus and algae could be the dryness of their habitats.
Structure
How lichens are arranged can be seen in detail under a microscope. Filament of the fungus (hyphae) braid colonies of unicellular algae. Outside, the fungal hyphae weave more densely, forming the so-called bark, and inside the weave is not so dense - this part is called the core.
Algal colonies try to be located as close to the upper and outer parts as possible. This is because the algae needs sunlight, because it feeds through photosynthesis.
Life forms
In nature, lichens are common enough for us. Just being in the forest, we can meet many representatives of this species. Basically, you can see three types:
- Limescale. They are more often found on stones, growing very densely to them.
- Leafy. You can see them on tree trunks. In shape, they look like layered growths.
- Bushy. They rise above the place where they grow in the form of "twigs".
Nutrition
Lichen consists of:
- Autotrophic organism - algae.
- Heterotrophic - a fungus.
Briefly described, it turns out that the fungus threads absorb water (water is absorbed by the entire surface of the body like a sponge) and minerals (moreover, the fungus is capable of literally extracting them from bare rocks, releasing substances that destroy the rock), and algae in cells In the process of photosynthesis, organic substances are formed, which, in turn, are absorbed by the fungus. But, as it turns out, everything happens much more complicated.
Scientists still have not been able to fully understand how the fungus is able to stimulate algae not only to produce the substances necessary for its nutrition, but also to release these substances in quantities greater than what happens with a separately existing algae. Separately existing algae releases into the environment only 10-15% of organic substances obtained by it during photosynthesis. Being in the composition of the lichen, this same algae will secrete 80−85%
synthesized organics that will be absorbed by the fungus.
It is believed that the fungus affects the cells of the algae with some chemicals, and this effect increases the amount of organic matter secreted by the algae. A direct physical effect is also possible, occurring through the contact of fungal hyphae and algae cells.
The ways of transferring organic substances from one participant of a compound organism to another are also not completely clear. Not so long ago, scientists managed to find out in the form of what substances the exchange of organics occurs. In one case, it is glucose, in the other - polyhydric alcohols.
Also an important component is nitrogen. Depending on what types of algae are part of this algae, this element can be obtained from:
- Air.
- Water.
- Substrate (stone, soil, plant bark).
The distribution of nitrogen compounds is closely monitored, and most of these substances are absorbed by the fungus.
Conditions of existence
Lichens are incredibly unpretentious organisms. They can grow, for example, on bare stones, many grow in the harsh conditions of the Far North or deserts.
The temperature range of life in these organisms is incredibly wide: from -70 to +60 degrees Celsius. They are able to exist in the absence of water, drying out, and then returning to life.
It is believed that these amazing organisms that can exist in almost the entire range of natural conditions on our planet are not able to live in anthropogenic environmental pollution. This does not apply to all forms, but in general, chemicals that are actively released during human activities into the environment are harmful to lichens.
The most unsuitable in this sense are bushy lichens. With air pollution, they will quickly die. A little less sensitive leafy. But scum are a form that managed to adapt to adverse conditions. They are able to live even in urban environments.
