Lichens are a symbiotic group of fungi, green algae and cyanobacteria. The name of the organisms comes from the similarity of their appearance with some skin diseases, and is translated from Latin as "lichen".
Description of symbiotes
They are distributed throughout the earth and can grow equally well in cold rocky terrain and in hot deserts. Their color can be of the most varied colors: red, yellow, white, blue, brown, black. The mechanism of lichen formation is not fully understood. But with accuracy we can say that their formation is influenced by sunlight. There are scale, fruticose and leafy lichens. The thalli of the former are similar to a crust that adheres tightly to the substrate. They are small (up to 2–3 cm), merge with each other, grow on the surface of tree trunks and rocks, forming conglomerates tens of centimeters in diameter. Bushy - more developed organisms that grow vertically and can reach several meters in height. But in this article we will take a closer look at the second type.organisms, the appearance and structure of leafy lichens, resembling the leaves of trees in their shape.
What are the structural elements of
Thallus or thallus is an integral part of unicellular or multicellular fungi, mosses and lichens. If compared with plants, then for them it is their young green branches. The thalli may be leaf-shaped or bushy.
Gifa is a filamentous formation resembling a cobweb. It is multinucleated and multicellular. And it is designed to absorb nutrients, water and, like a web, can be used to catch other organisms (for example, predator mushrooms).
Substrate is the surface to which the object is attached. It is also a breeding ground for some plants and lichens.
Appearance of foliose lichens
They have a rounded thallus, leaf-shaped and lamellar, sometimes consisting of one or more parts. And hyphae grow along the edges or along the radius of the circle. Leafy lichens have the form of a layered plate located on the substrate in a horizontal manner. The correctness of the shape of the thallus depends on the surface of the substrate. The smoother it is, the more rounded the lichen will look.
It is attached to the base with a thick short leg located in the center of the thallus. The plate itself with a diameter of no more than 20-30 cm is quite dense and leathery. Its shade can vary from dark green or gray to brown and black. They growvery slowly, but foliose lichens are somewhat faster than other varieties. In addition, they are long-lived. Some thalli are over a thousand years old. There is a direct relationship between the immobility of the substrate and the life span of the lichen.
Building
Foliate lichens have a two-level thallus due to their dorso-vertral structure. That is, they have an upper and lower surface. The upper part is rough or even, sometimes covered with outgrowths, tubercles and cilia, warthogs. On the bottom there are organs with which the lichen is attached to the substrate. In structure, it can also be smooth or uneven. Both parts differ not only in shape, but also in color intensity.
Under the microscope, four main anatomical layers are clearly visible:
- top cow;
- algae;
- core;
- lower cow.
Foliate lichens are loosely attached to the surface of the substrate and are easily separated from it. But between the thallus and the base an air cushion is formed. It nourishes the constituent parts of the lichen with oxygen, carrying out gas exchange, and contributes to the accumulation and preservation of moisture. The hyphae consists of special attachment organelles - the rhizoid.
Thallus is from one plate, then it is monophilic, or from several layers and is called polyphilic. The latter do not have a leg, their base is firmly attached to the surface, so they hold onto the substrate more firmly. They are not afraid of winds, hurricanes andother bad weather. The thallus can be dissected into lobes, cut along the edges, divided into lobes. Sometimes the appearance of a lichen resembles an intricately woven lace fabric.
Distribution
Foliose lichens grow in areas with high rainfall. They are easy to find on all continents, including even cold Antarctica. They can be placed on bare stones and rocks, on the trunks of shrubs and trees, mossy stumps, on old buildings. They grow along roads, in swamps, edges and dry meadows. Basically, their geographical location is precisely due to the choice of substrate. With the deterioration of the environment, lichens often change color closer to dark and gray. Ground organisms grow especially luxuriantly, covering vast areas of the earth. These include reindeer moss (Cladonia forest).
Types of foliose lichens
More than 25,000 species of lichens are spread all over the globe. If you divide organisms according to the substrate to which they prefer to attach, then there are:
- Epigean - located on soil or sand (for example, Brown Parmelia, Hypohymnia Nephrom, Solorina).
- Epilite - attached to stones, rocks (Gyrofora, Collem, Xanthoria, Cetraria).
- Epiphytic - grow on trees and bushes, mainly on leaves and trunks (Parmelia, Fiscia, Cetraria, Lobaria, Candelaria).
- Epixial - located on dead trees, stumps without bark, walls of old buildings (Hypohymnia, Parmeliopsis, Xanthoria).
It must be remembered that the same genus may include species with both foliose thalli and bushy thalli, or their intermediate forms.
Parmelia lichen
In its internal structure, it is very similar to green algae. Its surface can be yellow, brown with green, black and white patches. The genus Parmelia is a leafy lichen, which has about 90 species only in Russia, has a thallus cut into large pieces. Its blades can be both narrow and wider. It grows equally well on tree trunks and on stones, and adapts to the polluted urban climate. The form of this living organism is so diverse that it confirms the fact that it is not always advisable to classify lichens only in appearance. During World War II, parmelia powder was used to stop bleeding from wounds. It was also added to flour to protect it from pests and increase shelf life.
Foliate lichens, whose names are determined not only by the structure and shape, but also by the habitat halo, the type of substrate, are very diverse. Many of them are used in the food industry. They feed large and small cattle. Recently, powder from them has been widely used as food additives that make up pharmaceutical preparations. Cetraria, for example, are used in the manufacture of anti-diarrheals, to stimulate the immune system, normalize the organs of the digestive tract, as well asit is part of many antiviral drugs.
