What does a lichen consist of? Lichens in nature. Forms of lichens

After reading this article, you will find out what the lichen consists of, what forms of these plants meet, and also about the role they play in nature and in the economic activities of people. We will talk about how they absorb moisture, describe their metabolism.

Where do lichens grow?

Lichens are adapted to life even in the most severe conditions, often they are fixed where other living organisms can not exist. They go north and south further than other plants. In the Himalayas, they were found at altitudes of more than 5600 m.

Lichens, examples of which are numerous, can exist on almost any surface, whether it's a sun-scorched rock, a waterless desert, a beetle's back, or the whitened bone of a fallen animal. One species (Verrucaria serpuloides) lives permanently immersed in the icy waters of the Antarctic, while the other (Lecanora esculenta) is carried by the wind. And although in general lichens are very sensitive to any industrial waste, a species such as Lecanora conizaeoides, is markedly prosperous in rather polluted places.

Forms of lichens

In accordance with the growth characteristics, all known species of these plants (and their 15,000) are divided into three main groups. Briefly, we characterize each of them.

The leafy thrive in areas characterized by heavy rainfall. As you probably already guessed, they are named because of the fact that they resemble leaves in their shape. One of their types is presented in the photo below.

The next group is scaling (cortical). They are resistant to drought and therefore prevail in deserts. Scale lichens closely adhere to the substrate on which they grow. Caloplaca heppiana, for example, is often found on walls and gravestones. This and a number of similar species of plants of interest to us are used as indicators of the age of the substrate. Lichens of this group are often brightly colored, and the fungus is pigmented.

And finally, bushy are able to take moisture out of the air and are located mainly in areas of wet climate. The size and appearance of plants of interest to us are very diverse. Some of them form filaments of length 2.75 m and more, while others do not exceed a pinhead.

What does a lichen consist of?

These organisms are formed from plants belonging to two different departments: from algae and fungus. We will tell more in detail about what the lichen consists of. He is one of the most successful examples of mutualism. This term indicates a mutually beneficial partnership that can be established between two heterogeneous organisms.

The algal component is a necessary element of what the lichen consists of. This is usually either green or blue-green algae. Mushroom component - a representative of marsupials, or Ascomycetes. With rare exceptions, only those plants that consist of one species of fungus and one species of algae belong to lichens. Of the latter, the most common of these plants (more than 50% of the species) is the one-celled green alga Trebouxia, but there may be others.

So, lichens include organisms consisting of a fungus and algae that are in mutually beneficial cohabitation. Let us give one more example. Xanthoria parietina (pictured below) is commonly found on rocks along the sea coasts, as well as on walls and roofs of houses. Its orange saucer-shaped fruit bodies (apothecia) are almost indistinguishable in structure from the fruit body of an isolated fungus.

On the cut of the lichen, one can see a thin upper layer of densely intertwined fungal hyphae. It includes individual cells of green algae. Basically lichen is an organism whose body consists of loose intertwined mushroom hyphae, below which there is another thin layer of hyphae, similar to the upper one.

Growth of lichens

They grow very slowly. Most scale species rarely increase in size by more than 1 mm per year. Other forms of lichens grow a little faster, but they add no more than 1 cm per year. It follows that the large species of these plants have a very respectable age; Believe that some representatives of some Arctic species are older than 4000 years.

With the help of so-called lichenometry, i.e., measurements of lichens, even determine the age of the surface of the rocks. This method established the age of glaciers, as well as giant megaliths (large boulders). The latter were found on Easter Island in the Pacific Ocean.

The solid age of these plants shows that they have a fairly high organization and that the relationships between algae and fungus are well balanced. But the true nature of these relations is not yet quite clear.

Metabolism

Photosynthetic algae, like other green plants, provides food to both partners, since the fungus does not have chlorophyll. Simple carbohydrates, synthesized by algae, are excreted by it and absorbed by the fungus, where they transform into other carbohydrates. This exchange of carbohydrates also underlies the symbiotic relationship that led to the formation of lichens. The transfer of nutrients from the alga to the fungus occurs very quickly: it has been established that the fungi manage to convert sugars from algae within three minutes from the moment of the onset of photosynthesis.

Absorption of moisture

Lichens, absorbing a lot of moisture, significantly vary in volume. Their height significantly increases. Separation of organs that give up and absorb moisture, these plants are absent. The bark performs both of these functions. Lichens also do not have devices that protect them from transpiration, which are well developed, for example, in vascular plants. Most of the organisms of interest to us get moisture from the air, and not from the soil. They absorb water vapor. Only some species that attach to the substrate have the ability to take a part of the moisture out of it.

Use of Lichens

Lichens in nature are used in various ways: they serve as food for animals (for example, they make up two-thirds of the reindeer ration), used by birds as material for nests, serve as a refuge for many species of small invertebrates, such as ticks, beetles, butterflies and snails. They also benefit the person. Extracts from lichens were used once for the coloring of fabrics, from which were sewn Scottish skirts. Of these, yellow, brown, red and purple
paints. Intermediate colors were obtained by staining.

Icelandic moss (Cetraria islandica) has been used for more than two centuries as an anti-cough remedy. Present in some lichens, usnic acid is used by man for the treatment of superficial wounds and tuberculosis.

Modern studies have discovered antibiotics in them that are effective against diseases such as pneumonia and scarlet fever. In addition, these plants are used in industry. So, from lichen Roccella sp. A special litmus is produced - a chemical indicator that turns red in an acidic medium and blue in an alkaline one.