The lichen class is one of the most widespread and diverse organisms on Earth. Science knows more than 25 thousand of their species, the system of their distribution is still not fully understood. Their system of two elements has been arranged: fungus and algae; it is this composition that unites a huge variety.
What are scale lichens
The name "lichens" came from an analogy with lichen disease, arising from their appearance. Lichens are representatives of a unique species, known for those, in their composition there are simultaneously two organisms at once, algae and fungus. Many scientists distinguish a separate class for this species of fungus . Their combination is unique: the mushroom inside its body creates a special habitat in which the alga 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 scale lichens cover bare rocks, stones, grow on clay, on roofs and trees.
In a favorable environment, during photosynthesis, algae produces carbohydrates, which feeds the fungus. The latter is a parasite on her body, but their coexistence is, rather, a symbiosis. It is algae that is a life-forming component. If you isolate it from the fungus, in most cases it will be able to adapt to an independent, autonomous existence and will continue to develop independently. The mushroom will definitely die without the nutrition that it received.
Scales of lichen growth
Lichens are one of the most common microorganisms on the planet. In almost every latitude, scale lichens can be found that can adapt to any conditions. Adapted to the cold, they feel good on the slopes of the polar rocks, they are comfortable in the tropics and deserts.
Scale lichens are common throughout the planet; they do not require unique specific conditions. Depending on the type of substrate and the characteristics of the climate, one or another species grows on the ground. Expanding, they cover vast areas, completely filling the slopes of the rocks and covering the stones.
As a rule, groups are attached to climatic conditions or to the natural zone. Some species can be found only 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, in the mountains, etc. Also, distribution can be tied to certain soil features: some groups of lichens grow on clay, others on rocky soil, etc.
In addition, there is a small category of species that grow around the world, regardless of natural or climatic conditions.
Environmental Impact
In the ecological system of the planet, they are everywhere. The importance of lichens is great, these organisms perform a whole layer of work. They occupy the most important place in soil formation; they are the first to penetrate into the layers and enrich it for the further growth of other species. Scale lichens do not need a special substrate, covering the territory of barren soil, they enrich it and make it suitable for other plants. In the process of growth, they release special acids into the soil, due to which the earth becomes loose, it is weathered and enriched with oxygen.
The favorite environment for the growth of scale lichens, where they feel comfortable, is rocks. They confidently attach themselves to rocks and cliffs, change their color, gradually creating conditions for the development of other species on their surface.
Many animals have a color corresponding to one or another type of lichen that grows in their habitat. This allows you to disguise and protect yourself from predators.
External structure
The appearance of these symbiotic mushrooms is extremely diverse. Lichens, scum or cortical, are so named because they create on the surface where they grow a crust resembling scum. They can take a different shape and have unexpected colors: pink, blue, gray, lilac, orange, yellow or another.
Scientists distinguish 3 main groups:
• scale;
• leafy;
• bushy.
The characteristic signs of scale lichens are that they grow firmly to the ground or another substrate; it is impossible to remove them without damage. Such lichens are most common in cities where they can grow on concrete walls, trees. They can also often be found on the slopes. Wherever these lichens occur, their scale species do not require any essential conditions and feel great even on stones.
They represent a crust which covers surfaces unsuitable for life of other plants. Due to the peculiarities of their structure and appearance, they can be imperfectly invisible and merge with nature. Mistakenly, all such mushrooms are called moss; moss is only one of thousands of varieties of lower plants.
Distinguishing scale lichens from other species is very simple. Leaf attached to the soil with sprouts resembling small stems. The body of the lichen itself has a leaf-shaped appearance of various forms, their sizes can also fluctuate.
Bushy have the most complex external shape. They consist of twigs, round or flat, can grow on the ground, rocks. They are the largest, growing, can also hang from trees.
Scale lichens can have a transitional position between these groups and features of other species: this classification focuses solely on their external features.
Internal structure
The body of the scale lichen, or thallus (thallus), is of two types:
• homeomeric;
• heteromeric.
The first type is the simplest, in it algae cells are contained in a chaotic order and are distributed fairly evenly between the fungal hyphae. Most often, such a structure can be found in mucous lichen, for example, in scale-bearing lichens of the genus colema. In a calm state, they look like dried crusts, and under the influence of moisture instantly swell, becoming a leafy lichen. You can meet them on the Black Sea coast.
The heteromeric thallus of the lichen has a more complex structure. Most scale lichens are of this type. In the context of this type, its structured internal organization is traced. The top layer forms a mushroom, thus protecting the algae from drying out or overheating. Below the mushroom has branches that attach to the cells of the algae. Below is another layer of the neck, which is a substrate for algae, with its help the desired level of humidity and oxygen is maintained.
Lichen groups
The following groups are distinguished by type of growth and attachment to the type of substrate among scale lichens:
• epigeneous;
• epiphytic;
• epileptic;
• water.
The first group, epigeneous lichens, is distributed on various soils; they also grow quite well on stumps, rocks. They may well withstand competition with plants of higher groups, therefore, on sparse soils they grow infrequently, preferring fertile land. Some of them grow in dry swamps, along roads, in the tundra, where they occupy vast territories, etc. The most famous species are the hypocrite, pertusaria, ikmadofida.
Epigenea can also be divided into two more categories: moving (belong to other species) and lichens fixed on the soil, scaled to a greater extent. Attached scale deposits can exist on sandy, limestone, clay soil. Scales of lichen names in this group have the following: twisted ramalina, dark brown parmelia, colelema, pink beomitza and others.
Epiphytic lichens grow exclusively on trees or shrubs. They are conditionally also divided into two groups: epiphilic (exist on leaves, bark) and epixilic, arising on fresh sections. In most cases, they are found precisely on the bark, in a tiny area a couple of dozen different types of scale lichens can coexist at the same time, completely changing the color of the tree and creating an external new surface.
Scale lichens of the epilithic group settle on stones and rocky rocks. Their examples are diverse: some are planted exclusively on limestone, others prefer silicon rocks, others settle there and there, as well as on city roofs and walls.
Types of scale lichens
Scale lichens are of all four types accepted in science: epilithic, epigeneic, epiphytic and epixilic. They can grow on tree trunks, on dead wood, on stumps, but most often they grow on bare stones.
Scales of lichens grow on a wide variety of substrates. Examples can easily be found in any city or forest: on walls, roofs, stones, rocks. They grow so tightly to the soil that it is impossible to remove them without damage.
Scale lichens form a scum-like crust. They can have a very different color, and, completely covering the subject of the landscape, significantly change its appearance. Pink cliffs, violet, bright yellow stones make landscapes bright and unusual.
Aspicillia, hematoma, lecanor, lecidea, graphis, biator are the most famous scale lichens, examples of their growth are found almost throughout the country. A kind of biator can exist simultaneously in swamps and on stones. Lekanor scale lichen, for example, can grow on various substrates: both on stones, and on trees or stumps.
Scaling lichen propagation
There are three methods of reproduction: vegetative, sexual or asexual. Sexual reproduction is one of the most common methods: lichens form apothecia, perithecy, or gastrothecia - 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, gastrothecia begin to produce spores, which later germinate at the right temperature and humidity.
With asexual sporulation of lichens, spores arise and develop directly on the surface.
Tiny substances consisting of algae and fungus particles and thallus bushes participate in vegetative propagation. They spread with the wind or animals, traveling until they find a suitable substrate. This is the fastest method of reproduction, contributing to the rapid spread. Reproduction in this way can also occur with an unprepared piece of lichen, but in this case the chances of growing on a new substrate will be lower.
Application
The use of scale lichens is unusually wide: they are able to grow where there is no chance for any other plant. Over time, they prepare the necessary environment, a sufficient amount of humus for the growth of other plants. At the same time, out of the entire diversity of thousands of lichens, only two species are poisonous, the rest find their application in various 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 cough to oncology. Scale lichens are especially effective in treating purulent inflammations. They are carefully cut off from the surface and applied to the wound - thanks to the antibacterial properties and antiseptics that are contained in them, they destroy bacteria, help cleanse and heal an open wound.
Measurement of environmental conditions using lichens
In science, they are also used to study environmental conditions and air quality. Scale lichens are the most resistant to environmental degradation; they suffer environmental disasters and high levels of air pollution, but this significantly affects their condition. Due to the peculiarities of its structure, lichens absorb incoming water and air without additional filters, immediately with all thallus. Because of this, they are sensitive to pollution and changes in the composition of air or water, as toxins instantly disrupt their internal work.
Due to the high content of toxic substances in the atmosphere or water, there are cases of mass death of scale lichens. The first such cases began to occur near large industrial cities, where production is developed, and, consequently, a high level of air pollution. These cases have clearly demonstrated the need for filtering harmful substances into the air. Today, lichens are growing again in large cities due to their concern for the environment and improved air quality.
There are two directions for studying the state of air by the state of representatives of this species: active and passive. When passive, conclusions are drawn about the state of the atmosphere here and now, active means a long study of a certain type of lichen, which makes it possible to obtain a more accurate picture.