The relationship that occurs between algae cells and fungal hyphae in a lichen is called symbiosis
One or more algae cells surrounded by fungal hyphae and serving for vegetative propagation are called soredia.
217. Function of the algal layer of lichen:
1. aeration
2. protective
3. assimilating
4. attachment to the substrate
Sample answer: 3
218. Lichens settling on stones:
1. epiphytic
2. epigeic
3. epilithic
Sample answer: 3
219. Function of the lichen core:
1. aeration
2. assimilation
3. protective
4. reproduction
Sample answer:1
220. The classification of lichens is based on:
1. systematic affiliation of the photobiont
2. systematic affiliation of the mycobiont
3. life form
4. anatomical structure.
Sample answer: 2
221. The main method of reproduction of lichens:
1. sexual
2. asexual
3. vegetative
Sample answer: 3
222. During sexual reproduction of a mycobiont, the following are formed on the outside of the lichen:
1. fruiting bodies
2. sporangia
4. media
Sample answer:1
225. Lichen growth rate:
1. 5-10 cm per year
2. 5-10 mm per month
3. 2-3 mm per year
4. 1 cm per year
Sample answer: 3
226. An indicator of severe atmospheric pollution is the growth of lichens of the life form:
1. scale
2. leafy
3. bushy
4. no lichens
Sample answer: 4
227. Largest number species of known lichens have a life form:
1. scale
2. leafy
3. bushy
4. transitional between scale and foliate
Sample answer:1
228. Lichens are an important component of biogeocenoses, since:
1. photosynthesize
2. are “pioneers”
3. participate in the mineralization of organic substances
4. are “long-livers”
Sample answer: 2
229. Representatives of which division do not have a cell wall, the body is plasmodium?
1. slime mold
2. oomycots
3. zygomycotes
4. chytridiomycotes.
Sample answer:1
230. Representatives of this department are called “water molds”:
1. slime mold
2. oomycots
3. chytridiomycotes
4. zygomycotes
Sample answer: 2
231.For all representatives of c. Protoctista is characteristic:
1. absence of the embryo stage in the life cycle.
2. absence of sexual intercourse
3. unicellularity
4. lack of cell wall
Sample answer:1
232. The kingdom Protoctista includes:
1. mushroom-like organisms
2. algae and fungi-like organisms
3. plants, animals, mushrooms
4. lichens
Sample answer: 2
233. Archegonial plants include:
1. higher spore plants
4. mushroom-like organisms
Sample answer:1
234. The predominant generation in the development cycle of bryophytes is...
235. Fruit of cereals:
1. achene
2. winged nut
4. grain
Sample answer: 4
236. Sedge fruit:
3. box
4. lionfish
Sample answer:1
237. An inflorescence with sessile flowers on a common elongated axis is called:
1. earring
3. broom
4. simple ear
Sample answer: 4
238. Family of monocots:
2. Sedges
3. Nightshades
4. Lamiaceae
Sample answer: 2
239. Family with inflorescence spadix in representatives:
2. poppy
3. cloves
4. goosefoot
Sample answer:1
240. Cereals in the Krasnoyarsk Territory:
1. bushes
2. trees
4. subshrubs
Sample answer: 3
241. Species brought from other areas by humans:
1. apophytes
2. colonophytes
3. ergasiophytes
4. Advents
Sample answer: 4
242. Geobotany is the science of
1. lichens
2. plant communities
4. algae
Sample answer: 2
243. The plant community is:
1. biogeocenosis
2. biocenosis
4. phytocenosis
Sample answer: 4
244. Plants of highly saline soils and rocks:
1. xerophytes
2. mesophytes
3. hygrophytes
4. halophytes
Sample answer: 4
245. Leaf succulents:
2. young
3. camel thorn
Sample answer: 2
246. Plants – phanerophytes:
4. tulip.
Sample answer:1
247. The anemophilous line of evolution is characteristic of representatives of the families:
1. Ranunculaceae
2. Sedges
3. Orchids
4. Lilies
Sample answer: 2
248. Establish correspondence:
1. Lamiaceae A. cotton grass
2. Sedge B. jasmine
3. Liliaceae V. corn
4. Cereals G. tulip
1-B,2-A,3-G,4-B
249. The straw stem is characteristic of:
1. sedge
2. cereals
3. orchids
4. lilies
Sample answer: 2
250. Sclerification of the stem is characteristic of the family:
1. sedge
2. Lamiaceae
3. bluegrass
4. asteraceae.
Sample answer: 3
251. Triangular stems are a distinctive feature of the family:
1. bluegrass
2. sedge
3. Lamiaceae
4. asteraceae
Sample answer: 2
252. Unisexual flowers are characteristic of:
1. bluegrass
2. sedge
3. Asteraceae
4. orchids
Sample answer: 2
253. The tepals of the second circle of the Myatlikovy perianth are reduced and are called:
1. bractae
3. lodicules.
Sample answer: 3
254. Intercalary growth is expressed in:
1. bluegrass
2. sedge.
3. ranunculaceae
General characteristics. Lichens (Lichenes) are biologically very unique lower plants. A lichen is a complex organism formed as a result of the symbiosis of two plants: a fungus and an algae.
The bulk of the lichen thallus is a fungus, which tightly intertwines the algae cells with its hyphae. The constituent components of lichen - fungus and algae - complement each other. Algae are autotrophic plants containing chlorophyll and, therefore, capable of creating organic substances and supplying them to the fungus. The fungus is unable to photosynthesize, but has the ability to extract water and minerals and supply them to the algae. In addition, the fungus protects the algae from bright lighting, strong heating by the sun's rays and drying out.
You can artificially divide a lichen into its components - a fungus and an alga - and grow each component separately. In this case, the algae is usually able to continue its independent existence, but the fungus, which has adapted to coexistence that is beneficial for it, cannot develop independently without the algae and quickly dies. The structural features of lichens were first described in 1867 by Russian scientists A. S. Famintsyn and O. V. Baranetsky.
Lichens are characterized by very slow growth. "Reindeer moss" gives an increase of 2...3 mm per year.
Structure. Lichens are distinguished by their unique thallus structure. They are often mixed with another plant division - mosses. Lichens differ from mosses in the absence of division of the thallus into leaves and stems, as well as in color. Usually lichens have a gray or greenish-gray, yellow, orange color, etc. The typical green color characteristic of mosses is absent in lichens. Often the thalli of lichens have a bright color, which is caused by the presence of various acids in them.
Based on their external structure, lichens can be divided into 3 groups: crustaceous (or scale), leafy and bushy.
Crust (or crustose) lichens are the most diverse, and include most species of lichens. They are characterized by a simple structure. Representatives of this group of lichens have the appearance of crusts or plaques that tightly grow together with the substrate on which they live and from which they are separated with great difficulty. The substrate for crustose lichens is the bark of trees, the surface of stones and rocks. These lichens are considered the most primitive, they apparently gave rise to other lichens. These lichens are often found in the form of yellow-orange films, spots, and streaks on the bark of trees. From this group of lichens, graphis (Graphis sp.) is often found.
Foliaceous lichens have the appearance of dissected plates, fused with the substrate not very tightly with the help of bundles of hyphae (rhizin). These include parmelia (Parmelia sp.), growing on the bark of trees.
Fruticose lichens have thalli in the form of branching bushes; such lichens grow together with the substrate only at their base. A representative of bushy lichens can be the lichen, or bearded lichen (Usnea sp.), which grows in humid forests on tree branches in the form of long hanging bushes. This group of lichens also includes “oak moss” - evernia (Evernia prunastri Ach., E. furfuracea Mann.).
Based on the nature of the anatomical structure of the thallus, homeomeric and heteromeric lichens are distinguished. The homeomeric structure is more primitive. In a cross-section of a lichen with a homeomeric thallus structure, one can see that the algae are distributed more or less evenly throughout the thallus (Fig. 127).
With a heteromeric structure of the thallus, 4 layers are distinguished: upper crustal, gonidial, middle and lower crustal (Fig. 128). The upper crustal layer is a dense interweaving of fungal hyphae. Beneath it there is a layer of green algae called gonidial. Below the gonidial layer is the middle layer, consisting of loosely intertwined fungal hyphae. Beneath this layer is a lower layer consisting of tightly intertwined hyphae. Outgrowths - rhizines - extend from the bottom layer, with the help of which the lichen is attached to the substrate.
Reproduction. Lichens can reproduce in several ways. Both components - the fungus and the algae - can reproduce independently, independently of one another. Fungi form spores, from which hyphae develop, which together with algae form new specimens of lichens.
More often, lichens reproduce vegetatively - soredia and isidia. Soredia are microscopically small, dust-like lumps consisting of one or more algal cells entwined with fungal hyphae. Soredia are formed in the gonidial layer of the lichen and fall out in the form of dust through a rupture in the crustal layer. Having separated from the thallus, the soredia grow and give rise to a new lichen individual. Isidia are outgrowths on the upper side of the thallus. They also consist of a fungus and algae; at a certain period of development they break off, spread by water or wind, germinate and give rise to a new lichen individual.
Classification. There are about 20 thousand species of lichens. The classification of lichens is based mainly on the characteristics of the fungus; The structural features of the thallus are also taken into account. Typically, lichens are divided into 2 classes: marsupial lichens, which include the marsupial fungus, and basidiocial lichens, which include the basidiomycete fungus. Of the class of marsupial lichens, the most widespread is bushy deer lichen (Cladonia rangiferina Web.), known under the incorrect name “deer moss” (Fig. 129). It grows in harsh tundra conditions over a vast area and looks like small gray bushes 6...12 cm in height. This type of fruticose lichen, along with other related species, is an excellent food for deer. Contains in dry matter: carbohydrates - about 90%, protein - over 4%, fat - 2.5%, and ash - about 6%.
Distribution and ecology. Lichens are extremely sensitive to air purity; they cannot tolerate the slightest impurities of sulfur dioxide gases and therefore are absent in large industrial cities. They are able to withstand very high (up to 60 °C) and low (down to -60 °C) temperatures. Lichens are widespread in the tundra, high in the mountains on bare rocks. They prefer a stationary substrate and grow on trees (mainly on the north side), stones, fences, and walls.
Lichens tolerate drought well and quickly come to life at the first rain. All nutrition is obtained from air, precipitation and dust. They are found on substrates that cannot be colonized by other plants. Here they are pioneers of vegetation. Following them, other plants settle.
Origin. Representatives of marsupial fungi, less often basidiomycetes, take part in the formation of lichens. Lichens include green or blue-green algae.
The evolution of lichens took place mainly in changes in the thallus, in the direction of increasing its assimilating surface. Cruciform lichens are considered more ancient, primitive forms, and bushy lichens, which have a larger assimilating surface, are considered more advanced.
The meaning of lichens. Growing in very unfavorable conditions (on stones, rocks), lichens destroy the stone substrate due to the release of special acids.
In the harsh conditions of the tundra, “reindeer moss” is often the only food for large herds of reindeer. In winter, deer obtain this food from under the snow in pastures. In the Murmansk region, moss is fed to cows and sheep. In Iceland, another type of lichen that grows here and is known as Icelandic moss is used as food for reindeer. “Nomadic lichens” are common in semi-deserts and deserts of Asia and Africa. Such lichens lie freely on the soil surface in the form of small lumps and are easily transported by the wind over long distances. These lichens are consumed by the local population. Small, wind-movable lichens are sometimes called “lichen manna.” Some types of lichen are used to prepare paints and litmus.
Lichens are unique complex organisms, the thallus of which is a combination of a fungus and an algae that are in a complex relationship with each other, more often in symbiosis. Over 20 thousand species of lichens are known.
They differ from other organisms, including free-living fungi and algae, in shape, structure, nature of metabolism, special lichen substances, methods of reproduction, and slow growth (from 1 to 8 mm per year).
Structural features
Thallus lichens consists of intertwined fungal threads - hyphae, and algae cells (or threads) located between them.
There are two main types of microscopic structure of the thallus:
- Homeomeric;
- heteromeric.
On a cross section of a lichen homeomeric type there is an upper and lower cortex, which consists of a single layer of fungal cells. The entire internal part is filled with loosely arranged fungal threads, between which are located algae cells without any order.
In lichen heteromeric type of algae cells are concentrated in one layer, which is called gonidial layer. Below it is the core, consisting of loosely arranged threads of the fungus.
The outer layers of the lichen are dense layers of fungal filaments called cortical layers. With the help of fungal threads extending from the lower cortical layer, the lichen is attached to the substrate on which it grows. In some species, the lower bark is absent and it is attached to the substrate by pith threads.
The algal component of lichen consists of species belonging to the blue-green, green, yellow-green and brown divisions. Representatives of 28 genera of them enter into symbiosis with fungi.
Most of these algae may be free-living, but some are found only in lichens and have not yet been found in a free state in nature. While in the thallus, the algae change greatly in appearance, and also become more resistant to high temperatures and can withstand prolonged drying. When cultivated on artificial media (separately from fungi), they acquire the appearance characteristic of free-living forms.
The thallus of lichens is varied in shape, size, structure, and colored in different colors. The color of the thallus is due to the presence of pigments in the hyphal membranes and fruiting bodies of lichens. There are five groups of pigments: green, blue, violet, red and brown. A prerequisite for the formation of pigments is light. The brighter the lighting in places where lichens grow, the brighter they are colored.
The shape of the thallus can also be varied. According to the external structure of the thallus, lichens are divided into:
- Scale;
- leafy;
- bushy.
U crustose lichens the thallus has the appearance of a crust, tightly fused with the substrate. The thickness of the crusts varies - from barely noticeable scale or powdery deposits to 0.5 cm, diameter - from a few millimeters to 20-30 cm. Scale species grow on the surface of soils, rocks, the bark of trees and shrubs, and exposed rotting wood.
Foliose lichens have the shape of a leaf-shaped plate located horizontally on the substrate (parmelia, wall goldenrod). Usually the plates are round, 10-20 cm in diameter. A characteristic feature of leafy species is the unequal color and structure of the upper and lower surfaces of the thallus. In most of them, on the lower side of the thallus, organs of attachment to the substrate are formed - rhizoids, consisting of hyphae collected in cords. They grow on the surface of the soil, among mosses. Foliage lichens are more highly organized forms compared to crustose lichens.
Fruticose lichens have the form of an erect or hanging bush and are attached to the substrate by small sections of the lower part of the thallus (cladonia, Icelandic lichen). In terms of level of organization, bushy species are the highest stage of thallus development. Their thalli come in different sizes: from a few millimeters to 30-50cm. Hanging thalli of fruticose lichens can reach 7-8 m. An example is the lichen that hangs in the form of a beard from the branches of larches and cedars in taiga forests (bearded lichen).
Reproduction
Lichens reproduce mainly by vegetative means. In this case, pieces are separated from the thallus, carried by wind, water or animals and, under favorable conditions, give rise to new thalli.
In leafy and fruticose lichens, for vegetative propagation, special vegetative formations are formed in the surface or deeper layers: soredia and isidia.
Soredia look like microscopic glomeruli, each of which contains one or more algae cells surrounded by fungal hyphae. Soredia are formed inside the thallus in the gonidial layer of foliose and fruticose lichens. The formed soredia are pushed out of the thallus, picked up and carried by the wind. Under favorable conditions, they germinate in new places and form thalli. About 30% of lichens reproduce by soredia.
Nutrition
The nutritional characteristics of lichens are associated with the complex structure of these organisms, consisting of two components that obtain nutrients in different ways. The fungus is a heterotroph, and the algae is an autotroph.
The algae in the lichen provides it organic substances produced by photosynthesis. The lichen fungus receives high-energy products from the algae: ATP and NADP. The fungus, in turn, with the help of thread-like processes (hyphae) acts as a root system. This is how the lichen gets water and mineral compounds, which are adsorbed from the soil.
Also, lichens are capable of absorbing water from the environment with their whole body, during fogs and rains. To survive they need nitrogen compounds. If the algal component of the thallus is represented by green algae, then nitrogen comes from aqueous solutions. When blue-green algae act as phycobionts, nitrogen fixation from atmospheric air is possible.
For the normal existence of lichens they are needed in sufficient quantities light and moisture. Insufficient lighting interferes with their development, as photosynthetic processes slow down and the lichens do not receive enough nutrients.
Light pine forests have become the optimal place for their life. Although lichens are among the most drought-resistant species, they still need water. Only in a humid environment do respiratory and metabolic processes take place.
The importance of lichens in nature and human life
Lichens are very sensitive to harmful substances, so they do not grow in places with high dust and air pollution. So, they are used as indicators of pollution.
They take part in the cycle of substances in nature. Their photosynthetic part is capable of producing organic matter in places where other plants cannot survive. Lichens play an important role in soil formation; they settle on lifeless rocky surfaces and, after dying, form humus. This creates favorable conditions for plant growth.
Feeding lichens are an important link in the food chain. For example, deer, roe deer, and moose feed on reindeer moss or moss. Serve as material for bird nests. Lichen manna or Aspicilia edible is used in cooking.
The perfume industry uses them to make perfumes last longer, and the textile industry uses them to dye fabrics. There are also known species with antibacterial properties, which are used in the manufacture of medicines to combat tuberculosis and furunculosis.
Body structure
Lichens are a group of symbiotic organisms, the morphological basis of the body of which is formed by a fungus. Symbiosis refers to the mutually beneficial cohabitation of organisms belonging to different species. The body of lichens combines two components: autotrophic - algae or a cyanobacterium and a heterotrophic fungus, forming a single symbiotic organism. Each group of lichens is characterized by a constant form of cohabitation between a particular fungus and a particular alga that has developed during the process of evolution.
Lichens are varied in shape and size, their sizes range from several to tens of centimeters. The vegetative body is represented thallus, or thallus Depending on the structure of the thallus, there are scale, having the appearance of a crust, sheet And bushy.
Lichens are a unique group of complex organisms whose body 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” (IV-III centuries BC), gave a description of two lichens - spey and rochella - which were already then used to obtain aromatic and coloring matter. True, in those days they were often called either mosses, or algae, or even “the chaos of nature” and “the 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 the symbiosis of two different organisms: a heterotrophic fungus (mycobiont) and an autotrophic algae (phycobiont). In a lichen, both of these components enter into a close relationship: the fungus surrounds the algae and can even penetrate their cells. Lichens form special morphological types - life forms that are not found in the individual organisms that compose them." The metabolism of lichens has a specific character: only they produce 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 body of the lichen) is varied 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 membrane. Pigmentation helps protect the algal component from excessive light. Sometimes it happens the other way around: the lichens of Antarctica are colored black, which absorbs heat rays.
Based on the shape of the thallus, lichens are divided into crustose, foliose and bushy.
The thallus of crustose lichens has the appearance of a crust, tightly fused with the substrate by core hyphae. Sometimes it appears as a powdery coating.
Foliaceous lichens have the form of a plate located horizontally on the substrate, attached to it by outgrowths of hyphae - rhizines. The thallus can be whole or dissected, pressed to the substrate or rising above it.
The thallus spinosa lichen has the appearance of a branched erect or pendulous bush or unbranched erect columns. They are attached to the substrate by a short leg, widened at the end by a heel.
According to the anatomical structure, lichens are: 1) homeomeric, when algae are scattered throughout the body of the lichen; 2) heteromeric, when algae form a separate layer in the thallus. The top of the thallus is covered with a bark layer, consisting of cells fused with their walls and having the appearance of cellular tissue - plectenchyma. The bark plays a protective function and also strengthens the thallus. The attachment organs of foliose lichens are rhizoids and rhizina; the former consist of one row of cells, and the latter - of rhizoids connected into strands.
Lichens reproduce either by spores produced by the fungus, or by fragments of the thallus, that is, vegetatively,
Sexual reproduction of lichens is ensured by apothecia located on the upper side of the thallus and having a saucer shape. There, spores are formed as a result of the fusion of germ cells. The spores are spread by the wind and, once in favorable conditions, germinate into the hypha, but a new lichen will form only if the hypha encounters 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 around the globe indicates their enormous importance. Their role is especially great in the tundra and forest-tundra, where they form a noticeable part of the vegetation cover and where the life of a large group of animals is associated with them: they provide shelter for invertebrates and small vertebrate animals, food for them and for large vertebrates, such as reindeer. Icelandic moss lichen is used in northern countries as a supplement to pet food and as an additive for baking bread,
In all biogeocenoses, lichens perform photosynthetic and soil-forming functions. Especially when colonizing freshly exposed substrates, stony, rocky, and poor in organic matter.
In human economic activities, 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 indicator litmus, 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 in assessing air pollution and monitoring the radiation situation.
Materials from Andrey Ivanov’s personal page were also used
The lichen class is one of the most widespread and diverse organisms on Earth. Science knows more than 25 thousand of their species; their distribution system is still not fully understood. Their system consists of two elements: fungus and algae; it is this composition that unites a huge variety.
What are crustose lichens?
The name “lichens” comes from an analogy with the disease lichens, which arises due to their appearance. Lichens are representatives of a unique species, known for the fact that they simultaneously contain two organisms, an algae and a fungus. Many scientists allocate a separate class for this. Their combination is unique: the fungus inside its body creates a special habitat in which the algae is protected from external influences and provided with liquid and oxygen. The fungus consumes water from the substrate, absorbs oxygen, so the algae inside it receives nutrition and feels comfortable. Their existence does not require special soil; they grow wherever there is air and water, even in minimal quantities. Representatives of crustose lichens cover bare rocks, stones, grow on clay, on roofs and trees.
Areas where crustose lichens grow
Lichens are one of the most widespread microorganisms on the planet. In almost every latitude you can find crustose lichens that can adapt to any conditions. Adapted to cold weather, they thrive on the slopes of polar cliffs and are comfortable in the tropics and deserts.
Crustose lichens are distributed throughout the planet and do not require unique, specific conditions. Depending on the type of substrate and climate characteristics, one or another species grows in the area. As they grow, they cover huge areas, completely filling the slopes of rocks and covering the stones.
As a rule, groups are tied to climatic conditions or to a natural area. Some species can only be found in the Arctic, others only in the taiga. But in this system there are a number of exceptions, when the geography of growth is associated with environmental conditions that are repeated in different regions. These lichens live on the shores of freshwater lakes, oceans, mountains, etc. Also, the distribution may be tied to certain soil characteristics: some groups of lichens grow on clay, others on rocky soil, etc.
Implications for ecology
They are found everywhere in the planet's ecological system. The importance of lichens is great; these organisms perform a whole layer of work. They occupy a crucial place in the formation of the soil; they are the first to penetrate the layers and enrich it for the further growth of other species. Crustose lichens do not require a special substrate; covering the area of infertile soil, they enrich it and make it suitable for the life of other plants. During the growth process, they release special acids into the soil, due to which the soil becomes loose, weathered and enriched with oxygen.
The favorite growing environment for crustose lichens, where they feel comfortable, is rocks. They confidently attach to rocks and cliffs, change their color, gradually creating conditions on their surface for the development of other species.
Many animals have colors that correspond to one or another type of lichen growing in their habitat. This allows them to camouflage and protect themselves from predators.
External structure
The appearance of these symbiotic fungi is extremely varied. Lichens, crustose or crustose, are so called because they create a crust resembling scale on the surface where they grow. They can take different shapes and have unexpected colors: pink, blue, gray, lilac, orange, yellow or others.
Scientists distinguish 3 main groups:
Scale;
Leafy;
Bushy.
Characteristic signs of crustose lichens are that they grow firmly to the ground or other substrate, and it is impossible to remove them without damage. Such lichens are most common in cities, where they can grow on concrete walls and trees. They can also often be found on slopes. Wherever these lichens are found, their crustose varieties do not require any essential conditions and feel great even on stones.
They are a crust that covers surfaces unsuitable for life of other plants. Due to the peculiarities of their structure and appearance, they can be completely invisible and merge with nature. It is a mistake that all such mushrooms are just one of thousands of varieties of lower plants.
It is very easy to distinguish crustose lichens from other species. Leafy ones are attached to the soil with the help of sprouts that resemble small stems. The body of the lichen itself has a leaf-like appearance of various shapes, their sizes can also fluctuate.
Bushy ones have the most complex external shape. They consist of twigs, round or flat, and can grow on the ground and rocks. They are the largest, and as they grow, they can also hang from trees.
Crumbose lichens may have a transitional position between these groups and features of other species: this classification is focused solely on their external characteristics.
Internal structure
The body of crustose lichen, or thallus (thallus), comes in two types:
Homeomeric;
Heteromeric.
The first type is the simplest, in which the algae cells are contained in a chaotic order and are distributed quite evenly between the hyphae of the fungus. Most often, this structure can be found in slimy lichens, for example, in crustose lichens of the genus Collema. In a calm state, they look like dried crusts, and under the influence of moisture they instantly swell, taking on the appearance You can meet them on the Black Sea coast.
The heteromeric thallus of lichen has a more complex structure. Most crustose lichens belong to this type. In the context of this type, its structured internal organization can be traced. The top layer forms a mushroom, thus protecting the algae from drying out or overheating. Below, the fungus has branches that attach to the algae cells. Below is another layer of the vulture, which is a substrate for algae, with its help the required level of humidity and oxygen is maintained.
Lichen groups
According to the type of growth and attachment to the type of substrate, the following groups are distinguished among crustose lichens:
Epigeal;
Epiphytic;
Epiletaceae;
The first group, epigeic lichens, are common on various soils; they also grow well on stumps and rocks. They can easily withstand competition with plants of higher groups, so they grow infrequently on poor soils, preferring fertile soil. Some of them grow in dry swamps, along roads, in the tundra, where they occupy vast territories, etc. The most famous species are Lyceum, Pertusaria, Ikmadofida.
Epigeic lichens can also be divided into two more categories: moving lichens (related to other species) and soil-fixed lichens, which are mostly crustose. Attached scale can exist on sandy, limestone, and clayey soils. The names of crustose lichens in this group are as follows: twisted ramalina, dark brown parmelia, collema, pink beomycets and others.
Epiphytic lichens grow exclusively on trees or shrubs. They are also conventionally divided into two groups: epiphilic (exist on leaves, bark) and epixyl, arising on fresh cuts. In most cases, they are found precisely on the bark; a couple of dozen different types of crustose lichens can simultaneously coexist in a tiny area, completely changing the color of the tree and creating a new external surface.
Crustose lichens of the epilithic group settle on stones and rocky rocks. Their examples are diverse: some grow exclusively on limestones, others prefer silicon rocks, others settle here and there, as well as on city roofs and walls.
Types of crustose lichens
Crustose lichens come in all four types accepted in science: epilithic, epigeic, epiphytic and epixyl. They can grow on tree trunks, on dead wood, on stumps, but most often they grow on bare rocks.
Crustose lichens grow on a variety of substrates. Examples can easily be found in any city or forest: on walls, roofs, stones, cliffs. They grow so tightly to the soil that it is impossible to remove them without damaging them.
Crustose lichens form a crust similar to scale. They can have a wide variety of colors, and, completely covering a landscape object, significantly change its appearance. Pink and purple rocks make the landscapes bright and unusual.
Aspicilia, hematoma, lecanora, lecidea, graphis, biatora are the most well-known crustose lichens; examples of their growth are found almost throughout the country. A species of biator can exist simultaneously in swamps and on rocks. Lecanora crustose lichen, for example, can grow on various substrates: on stones, trees or stumps.
Reproduction of crustose lichens
There are three methods of reproduction: vegetative, sexual or asexual. Sexual reproduction is one of the most common methods: lichens form apothecia, perithecia or gasterothecium - these are various bodies within the body in which spores develop. Their development is extremely slow and can last up to 10 years. After this process is completed, gasterothecium begins to produce spores, which subsequently germinate at the right temperature and humidity.
With asexual sporulation of lichens, spores arise and develop directly on the surface.
Vegetative propagation involves tiny substances consisting of particles of algae and fungus, and thallus bushes. They are spread by wind or animals, traveling until they find a suitable substrate. This is the fastest method of reproduction, facilitating rapid spread. Reproduction in this way can also occur with an unprepared piece of lichen, but in this case the chances of growth on a new substrate will be lower.
Application
The use of crustose lichens is unusually wide: they are able to grow where no other plant has a chance. Over time, they prepare the necessary environment, a sufficient amount of humus, for the growth of other plants. Moreover, out of the entire multi-thousand variety of lichens, only two species are poisonous, the rest find their use in different fields: in agriculture, medicine.
The use and importance of lichens in pharmacology is also great: healers in villages know the beneficial properties of each of hundreds of species, using them to treat a wide range of diseases: from coughs to oncology. Scale lichens are especially effective in treating purulent inflammation. They are carefully cut off from the surface and applied to the wound - thanks to the antibacterial properties and antiseptics contained in their composition, they destroy bacteria and promote cleansing and healing of the open wound.
Measuring environmental health using lichens
In science, they are also used to study environmental conditions and air quality. Crustose lichens are the most resistant to deteriorating natural conditions; they tolerate environmental disasters and high levels of air pollution, but this significantly affects their condition. Due to the peculiarities of their structure, lichens absorb incoming water and air without additional filters, with the entire thallus at once. Because of this, they are sensitive to pollution and changes in air or water composition, as toxins instantly disrupt their internal functioning.
Due to the increased content of toxic substances in the atmosphere or water, cases of mass death of crustose lichens occur. The first such cases began to occur near large industrial cities, where production is developed, and, consequently, there is a high level of air pollution. These cases clearly demonstrated the need to filter emissions of harmful substances into the air. Today, lichens are growing again in major cities thanks to environmental concerns and improved air quality.
There are two directions for studying the state of air according to the state of representatives of this species: active and passive. With passive, conclusions are drawn about the state of the atmosphere here and now; active involves a long-term study of a certain type of lichen, which makes it possible to obtain a more accurate picture.