What are lichens and their types

Although the different plants that grew on the bark of olive trees and other trees were originally called lichens, and later the word was used as an alternative of equal meaning to moss, currently its study is much more developed and its meaning is different. In fact, lichen is the symbiotic fusion of a fungus with an organism capable of photosynthesis , be it a cyanobacterium or an alga. Due to this peculiar nature, which gives the union of the two organisms characteristics that they do not have separately, they are also commonly called lichenized fungi . Its two components are called mycobiont or mycosymbiont (this being the fungal part) and photobiont (This is the part capable of photosynthesis).

Among the main characteristics of lichens we find that:

• The lichen shape is almost always dominated by the mycobiont.
• The photobiont, for practical reasons, tends to be located on the periphery of the lichen, where it can collect light.
• Recently a third component was discovered in the symbiosis present in many species of lichens: a Basidiomycota yeast .
• They are capable of surviving very long droughts, sometimes even years.
• It is always the photobiont that provides energy to the whole, with the mycobiont in charge of providing its resistance to desiccation. Thus, both can live in environments where they would not be able to do so separately.
• They can live in a huge variety of habitats, from the tropics to the poles.

So that you can better understand the relationship between these beings, we recommend that you expand the information on What is symbiosis with examples .

7 types of lichens are distinguished if we look at their way of adhering to the substrate and their morphology.

• Foliaceous: are those that develop on the surface of the substrate, spreading through it and fixing itself thanks to its ricins or in a single point. Some examples are Xanthoria, Physcia, or Umbillicaria.
• Fruity: these lichens tend to take the form of shrubs of reduced size, and they attach to the substrate at a reduced point or surface of union. They are fruiting lichens Usnea, Alectoria and Ramalina.
• Scaly: their edge is not glued to the substrate, and they take the form of a tapestry of scales very close to each other. An example of this is the Psora.
• Filamentous – Some of these look a lot like fruity ones. They form a network of threads or filaments, of very fine thickness and usually entangled. The Cystocoleus is one of them.
• Gelatinous: when they have enough moisture, their texture becomes fleshy and flexible, soft. In addition, in this state of abundance of water they can become translucent.
• Crustaceans: they are the most numerous of the known lichens. As their name suggests, they adhere with great strength to the substrate in which they develop, which is usually rocks, although sometimes they also adhere to dead wood, leaves or logs, as well as soil or humus.
• Compounds: they have two thalli, a main one that is almost always scaly or crustacean and a secondary one, which is fruity.

Lichens are organisms of great ecological importance , and here are some of the main reasons:

• They are one of their most important functions that of colonizers in almost all primary ecosystems.
• Due to their great resistance and unique characteristics, they can grow and develop in very hostile and arid environments, and when they die they form part of the humus that enriches the nutrients of the soil so that plants and other organisms can flourish in it.
• In addition, there are lichens that release acidic substances when they die, thus contributing to the degradation of rocks and the formation of more habitable soil.
• They are also suitable for human food consumption , and there are several countries that habitually consume them as part of their gastronomies.
• They are also used as components of perfumes and colorants, for the manufacture of cosmetics.
• In medicine they have been traditionally used for their great antibiotic properties . Modern medicine uses them in antitumor, antifungal, anti-inflammatory and also antibiotic drugs.
• In addition, they are a great gauge of air quality , since they are very long-lived and at the same time sensitive to polluted air, although they have a great capacity to recover when conditions are suitable again.

If you liked this information about what lichens are, the types there are and their importance and if you want to discover more about the world of fungi and what other characteristics they have, apart from the fact that some are capable of having such a relationship with photosynthetic organisms We recommend you read this other AgroCorrn article about the Fungi Kingdom: what it is, characteristics, classification and examples .