The structure and nutrition of lichens. Lichens - biology exam

The structure of pipes Water and gas pipes are made by butt welding with a nominal diameter Bu from 6 to 150 mm with a wall thickness S from 1.8 to 5.5 mm and a length of 4 to 12 m. At the request of the consumer, metric threads are cut at the ends of the pipes. The ends of the pipes are cut at right angles to the axis

2.1. The structure of the gooseberry 2.1.1. Root system Cultivated plants have roots of two kinds.

body structure

Lichens are a group of symbiotic organisms the morphological basis of the body of which forms a fungus. Symbiosis is the mutually beneficial cohabitation of organisms belonging to different species. Two components are combined in the body of lichens: autotrophic - seaweed or cyanobacteria and heterotrophic - fungus, forming a single symbiotic organism. Each group of lichens is characterized by a constant form of cohabitation of a certain fungus with a specific algae that has developed in the process of evolution.
Lichens vary in shape and size, ranging in size from a few to tens of centimeters. The vegetative body is represented thallus, or thallus. Depending on the structure of the thallus, they distinguish scale, having the appearance of a crust, leafy and bushy.

Lichens are a peculiar group of complex organisms, the body of which consists of two components - a fungus and an algae. As organisms, lichens were known long before the discovery of their essence. Even the great Theophrastus, the "father of botany" (4th-3rd centuries BC), gave a description of two lichens - succulent and rochella - which were already used to obtain aromatic and coloring substances. True, in those days they were often called either mosses, or algae, or even "chaos of nature" and "wretched poverty of vegetation",

About 20,000 species of lichens are now known. The science of lichens is called lichenology. A specific feature of lichens is a symbiosis of two different organisms: a heterotrophic fungus (mycobiont) and an autotrophic algae (phycobiont). In a lichen, both of these components enter into close relationships: the fungus surrounds the algae and can even penetrate into their cells. Lichens form special morphological types - life forms that are not found in individual organisms that compose them. "The metabolism of lichens has a specific character: only they form lichen acids that are not found in other organisms. The methods of reproduction of lichens as integral organisms are also specific.

The thallus (the so-called lichen body) is diverse in shape, size, color and structure. The color of lichens varies: they are white, gray, yellow, orange, green, black; this is determined by the nature of the pigments contained in the hyphal sheath. Pigmentation helps protect the algal component from excessive light. Sometimes the opposite happens: the lichens of Antarctica are painted black, which absorbs heat rays.

According to the shape of the thallus, lichens are divided into scale, leafy and bushy.

The thallus of scale lichens has the form of a crust, tightly fused with the substrate with core hyphae. Sometimes it is represented by a powdery coating.

Leafy lichens have the form of a plate, horizontally located on the substrate, attached to it by outgrowths of hyphae - rhizins. The thallus can be whole or dissected, pressed against the substrate or rising above it.

Thallus spinous lichen has the form of a branched standing or drooping bush or unbranched standing columns. They are attached to the substrate with a short leg, expanded at the end with a heel.

According to the anatomical structure, lichens are: 1) homeomeric, when algae are scattered throughout the body of the lichen; 2) heteromerous, when algae form a separate layer in the thallus. From above, the thallus is covered with a bark layer, consisting of cells growing together with their walls and having the appearance of a cellular tissue - plectenchyma. The bark plays a protective function, and also strengthens the thallus. Organs of attachment of leafy lichens rhizoids and rhizines; the former consist of a single row of cells, and the latter consist of rhizoids connected into strands.

Lichens reproduce either by spores that the fungus forms, or by fragments of the thallus, that is, vegetatively,

Sexual reproduction of lichens is provided by apothecia located on the upper side of the thallus and having a saucer-shaped shape. There, spores are formed as a result of the fusion of germ cells. Spores are dispersed by the wind and, once in favorable conditions, germinate into a hypha, but a new lichen will form only if the hypha meets a suitable algae.

Vegetatively, lichens reproduce by isidia and soredia - outgrowths on the thallus containing both components of the lichen.

The wide distribution of lichens on the globe testifies to their great importance. Their role is especially great in the tundra and forest-tundra, where they make up a significant part of the vegetation cover and where the life of a large group of animals is associated with them: they are a refuge for invertebrates and small vertebrates, food for them and for large vertebrates, such as reindeer. Iceland moss lichen is used in the Nordic countries as a supplement to pet food and as an additive in bread baking,

In all biogeocenoses, lichens perform photosynthetic, soil-forming functions. Especially when settling freshly exposed substrates, stony, rocky, poor in organic matter.

In human economic activity, lichens can be used as producers of lichen acids - compounds with antibiotic properties. The widespread use of lichens in medicine is based on their tonic and antiseptic properties. The lichen acids they produce have antimicrobial activity against staphylococci, streptococci, tubercle bacilli, and are also successfully used in the treatment of dermatitis.

Since ancient times, the use of lichens in perfumery has been known, based on the high content of aromatic substances and essential oils in their thalli. In particular, oak moss is used in the manufacture of perfumes.

This group of plants has also been known as dyes for a very long time, and Scottish tweed is still dyed with lichen extracts. The litmus indicator widely used in chemistry is also a derivative of lichens.

Lichens are sensitive to the presence of harmful impurities in the air, especially those containing heavy metals. Recently, they have been widely used to assess air pollution and to control the radiation situation.
Also used materials from the personal page of Andrey Ivanov

These amazing plants are an example of the mutually beneficial living of fungi and algae, less often fungi and cyanobacteria. It even happens that the three of us cohabit: mushrooms (mandatory) and algae + cyanobacteria. Such cohabitation is called obligate symbiosis.

Lichen species for different characteristics

There are two-component lichens and three-component. Depending on the number of components in them.

Based on the appearance of the thallus (thallus), lichens can be divided into the following groups:

• scale lichens. The smallest and longest-lived, grow mainly on stones, rocks, concrete walls, trees, old fences. They are difficult to separate from the subject on which they grow;
• foliose lichens - these associates can no longer be attached to the substrate with their whole body, but only with one edge (outgrowths - rhizoids), they are easily separated, they look like a leaf. Grow on stones, stumps, long lying objects such as rusty iron, glass, slate;
• fruticose lichens the most developed. They grow upwards (unlike the first two) and have a bushy appearance. Attached mainly to the ground or trees. They are in the form of twigs or threads. They can grow up to 6 - 7 meters.

Behind the internal structure, this symbiosis can be grouped as follows:

• heteromeric - the body of the lichen on the cut is clearly divided into layers of fungus and algae;
• homeomeric - the components are randomly mixed inside the thallus.

After the place of growth, lichens are divided:

• epigeic (grow on the ground);
• epilithic (grow on stones);
• epiphytic (grow on tree trunks).

Mutual benefit of mushrooms and algae

So why live together, in the same body, fungi and algae? But why: algae need water (moisture) for normal life, and the fungus needs ready-made food - he himself will not cook anything from water and light (as almost all plants do), so he, a heterotroph, feeds on the products of photosynthesis of algae ( autotrophs) to which it provides moisture. He accumulates it in himself like a sponge.

Where do lichens grow

Probably everyone knows that lichens are the pioneers of the area. Often, in areas that have not yet been inhabited, due to some circumstances (fires, land reclamation, volcanic eruptions, drainage of territories), lichens appear first. Moreover, they serve as excellent fertilizer and food for other organisms.

These plants can survive in extreme conditions. Their scale ranges from -47 degrees Celsius to plus 80 ºC. They can withstand both acidic and alkaline influences, and even strong ultraviolet radiation. Which is not typical for other plants. The habitat is also large: from the far north to Antarctica.

The role of lichens in the life of animals and humans

Although these organisms are inconspicuous, their significance is important for other living beings, in particular for the inhabitants of the northern territories. In the harsh Siberian winters, Yagel lichens or reindeer moss, Icelandic moss are the main food for deer, and also elk and roe deer look for them under the snow. Many birds use it as nest litter.

There are edible lichens for humans as well. This is Bryoria Fremont, an edible aspicilia. Especially love them in China, Japan. For medicinal purposes, Icelandic cetraria, Lobaria are used. For the manufacture of dyes, the litmus indicator, the odor fixative, in perfumery, lichens are used everywhere.

The thallus of leafy lichens has the form of a leaf-shaped plate, horizontally spread on the substrate. The most characteristic of it is a rounded shape, which is due to the horizontal-radial growth of hyphae. At the beginning of the formation of the thallus, the hyphae of foliose lichens grow from one rudiment along the radii of the circle. In adult plants, marginal growth of hyphae is also observed. Usually young thalli have a regular rounded shape, but later they begin to grow unevenly and their shape becomes irregular. Usually the shape of the thallus is determined by the nature of the substrate. The smoother its surface, the more regular rounded shape the thalli of foliose lichens have.

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 dark gray, dark brown or black (Fig. 292). The thallus, consisting of one leaf-shaped plate, is called monophyllic. The monophyllic lamellar thallus is usually attached to the substrate only in its central part with the help of a thick short stalk called gomf (Fig. 292, 2a). This form of thallus is possessed by representatives genus Umbilicaria(Umbilicaria) and some species genus Dermatocarpon(Dermatocarpon). These are xerophytic forms widely found on rocks in the Arctic, Antarctic and highlands. Thick dense leathery thalli of these lichens, securely attached to the surface of the substrate with a thick short stalk, easily endure the action of strong winds, snow storms, hurricanes, and there can be long periods without water. Sometimes such thalli do not consist of one, but of several leaf-shaped plates, and then they are called polyphilic (Table 42, 3, 4, 5).

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Often, the lamellar thallus is notched along the edges or dissected into wide lobes. An example is the large-leaved thallus species kind of peltiger(Peltigera), which are often found in forests on the soil among moss or on the bases of tree trunks overgrown with moss (Table 42, 3). In moist old shady forests, on tree trunks or mossy rocks, intricately carved coarse-grained thalli grow. lobarium(Lobaria) and stick(Sticta, pl. 47, 1, 4). These lichens are usually quite loosely attached to the substrate with their entire lower surface, only the edges rising upward remain free.

More complex in structure is the leafy thallus, dissected into many small lobes. These lobes are of very different sizes and shapes: narrow and wide, weakly and strongly branched, flat and convex, closely closed and divided, overlapping each other with their edges or strictly delimited (Table 47). As a rule, they are collected in rounded rosettes, but sometimes they form thalli of indefinite, infinitely diverse shapes - in appearance they resemble skillfully woven lace, enveloping the trunks and branches of trees with a multi-colored cover (Table 42, 6).

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A characteristic feature of the leafy lichen thallus is its dorsoventral structure, in which the upper surface differs in structure and color from the lower one. For example, representatives kind of peltiger(Peltigera) the upper side of the thallus is grayish or grayish-brownish, smooth or slightly rough, and the lower side is whitish, pinkish, often black-gray in the center, felty, with numerous veins and shaggy strands of attachment hyphae. Species genus hypohymnia(Hypogymnia) the upper side is smooth, gray, and the lower side is black. Lichen solorin scortea(Solorina scortea), the thallus is grayish-brown above, and bright, reddish-orange below (Table 42, 4).

The upper surface of the thallus of leafy lichens is smooth, wavy, pitted, bare, glossy or matte, often rough, uneven, covered with tubercles, warts. Sometimes it has outgrowths of various shapes, cilia that form pubescence or a felt coating.

The lower surface is also diverse in its structure, but its characteristic feature is that it almost always forms special organs with which the foliose lichen is attached to the substrate. Unlike crustaceous lichens, whose thallus is entirely tightly fused with the substrate, foliose lichens are usually quite loosely associated with it and in most cases can be easily separated from it. Only a very few species, such as representatives of the genus hypohymnia, are attached to the substrate directly by the lower crustal layer. But even in this case, there is no dense fusion of the substrate and the entire lower surface of the lichen - the thallus is attached in separate sections of the lower surface. In the vast majority of foliose lichens, special attachment organs are formed on the underside of the thallus - rhizoids, rhizins or gomphs. They are formed by strands of hyphae and differ from each other in anatomical structure. In species of the genus Anzia, common in the tropical and subtropical regions of Asia, America, Australia and Oceania, and in the USSR found in the Far East, a spongy underlayer is formed, with the help of which these lichens are attached to the substrate (Fig. 290, a).

Leafy lichens are much more highly organized forms compared to scale ones. In evolutionary terms, it turned out to be beneficial to separate the thallus from the substrate. A small gap appeared between them, and this gave a number of advantages. Firstly, it contains a layer of air, which contributes to a better gas exchange of the inner layers of the thallus. Secondly, moisture lingers there longer, due to which the thallus can be in a wet state for a longer time. Thirdly, in the narrow space between the surface of the substrate and the thallus, various organic and inorganic substances that can be used by the plant usually linger.

But, on the other hand, having separated from the substrate, the lichen doomed itself to a lot of inconvenience. It became more vulnerable to environmental factors - the action of the wind, the impact of rain and snow, the attack of animals, etc. And first of all, the lower surface of the lichen turned out to be unprotected.

The progressive role of the separation of the lichen from the surface on which it grew consisted in the complication of the anatomical structure of the thallus and the development of special organs of attachment. First of all, the lower crustal layer appeared on the thallus, which is usually absent in scale forms of lichens. The vast majority of leafy lichens have a well-developed crustal layer on the underside of the thallus. The exception is the large-leaved peltiger thalli. The lower surface of these lichens is lined with loosely arranged core hyphae, which also form long bundles of rhizoidal cords penetrating into the substrate. These lichens usually grow on the soil, among mosses. The peculiar structure of the lower surface, the absence of the lower crustal layer, allow these plants to better and faster draw moisture from wet tufts of mosses.

However, the separation of the thallus from the substrate led not only to the formation of a crustal layer on the underside of the lichens, but also to the complication of the anatomical structure of the entire thallus. In contrast to scale lichens, in leafy forms in thalli there is a clear differentiation of anatomical layers. As a rule, under a microscope on transverse sections of such thalli, 4 well-differentiated layers can be distinguished: the upper crustal layer, the algae layer, the core and the lower crustal layer. The structure of the crustal layers, which play here not only a protective, but also a strengthening role, reaches a particularly large variety in foliose lichens.

Among foliose lichens, loose, nomadic forms are also found. In the steppes of the south and southeast of our country and in Mongolia, one can usually find free-lying greenish-black thalli on the soil surface. wandering parmelia(Parmelia vagans, pl. 50). They are not attached to the substrate and are freely carried by the wind from place to place. In the mountain tundras of Siberia and Chukotka, on dry mountain slopes and gently sloping hills, another very beautiful nomadic lichen lives. Cetraria Richardson(Cetraria richardsonii, pl. 47, 2). When dry, its dark brown thalli shrink and curl into lumps, which, like miniature perekatipoles, wander from place to place with the help of the wind.

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Plant life: in 6 volumes. - M.: Enlightenment. Under the editorship of A. L. Takhtadzhyan, editor-in-chief corr. USSR Academy of Sciences, prof. A.A. Fedorov. 1974 .

See what "Foliate lichens" are in other dictionaries:

foliose lichens- lichens characterized by b. m. horizontally prostrate thallus in the form of an uneven plate of various shapes ... Glossary of botanical terms

A group of lichens, the thallus of which has the form of a leaf-shaped plate, horizontally located on the substrate. Usually it is round (due to the radial growth of hyphae), but in old lichens it acquires an irregular shape. Diam. 10 20 cm. Often ... ...

- (Lichenes), organisms formed by the symbiosis of a fungus (mycobiont) and algae (phycobiont); traditionally referred to as lower plants. Early fossil L. presumably attributed to the top. chalk. Occurred as a result of the transition of some representatives ... ... Biological encyclopedic dictionary

Polyphyletic group of fungi Ernst Heinrich Haeckel ... Wikipedia

Lichens react differently to air pollution: some of them cannot stand even the slightest pollution and die; others, on the contrary, live only in cities and other settlements, having adapted well to the corresponding ... ... Biological Encyclopedia

- (Lichenes) a specialized group of fungi that are in constant cohabitation with algae; some botanists consider L. as an independent group of lower plants. The science of L. is called lichenology (See Lichenology). ... ... Great Soviet Encyclopedia

Yageli, spore-bearing plants, fungi and algae cohabitate in the body. Fungal cells and algae cells exchange nutrients through assimilation: the former give water and minerals and receive organic substances from the latter ... ... Agricultural dictionary-reference book

Lichens can be found almost everywhere, even in Antarctica. This group of living organisms has been a mystery for 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 and enrichment with oxygen.

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.