Classification of lichens by Unacademy

A lichen, rather than being a single creature, is a symbiosis of various species such as fungus and cyanobacteria or algae. Cyanobacteria are commonly referred to as blue-green algae, despite the fact that they are not algae. Chlorophyll is found in photobiont, which is a non-fungal component. One photobiont and one mycobiont are common lichen partners, although this is not always the case; some lichens have many photobiont partners.

The fungal partner is assumed to be made up of filamentous cells called hypha. These hyphae can branch, but they maintain a constant distance between them and increase through extension.

Lichens grow in less polluted areas and come in a variety of colours, sizes, and shapes. We shall learn about the various species of lichens and their economic relevance in this article.

Lichen

A few lichens exhibit filamentous formations among photobionts, whereas others are formed up of chains of more or fewer cells. Ascomycetes or Basidiomycetes species are the most common fungus in lichens. The most common algal partners are green algae (Chlorophyta) or blue-green bacteria (Cyanophyceae).

Although algae may typically thrive on their own in water or damp soil, most fungal partners cannot survive without their phycobiont. Although the largest lichens can produce thallus up to 3 feet long, the most are only a few millimetres long. They have a wide range of colours, from yellow to green to black.

Lichen Habitat

Lichens grow in less polluted environments. They grow on barren rock, wood logs, tree trunks, soil, and abandoned walls, among other things. Some of them can be found in watery environments. Lichens can grow anywhere from sea level to high alpine elevations, on almost any surface, and in a variety of environments.

Characteristics of Lichen

Lichens have a number of distinguishing characteristics, some of which are mentioned here for your convenience.

Lichens are a type of composite thalloid plant that is formed when algae and fungus come together.
Both use the carbohydrate produced by the algal partner during photosynthesis, while the fungal partner is responsible for water absorption and retention.
Thalli are characterised as crustose, foliose, or fruticose based on their morphological structure.
Lichen reproduces in three different ways: vegetative reproduction, asexual reproduction, and sexual reproduction.
Basidiospores resemble bracket fungus and are produced by Basidiolichen. Near the bottom of the fruit body, basidiospores develop.
Lichen is a slow-growing fungus that can survive in difficult conditions such as high temperatures and dry weather.

Economic Importance of Lichens

Lichens are used for a variety of purposes, including:

Roccella tinctoria is used to make orchin dye.
Rochella montagnei is the source of litmus.
Cladonia rangiferina (Reindeer moss) is a nutritious and antibiotic-rich plant.
In the perfume industry, Ramalina and Evernia are used.
Lichens are signs of air pollution. They don’t grow in areas where there’s a lot of SO2.
Many lichens, such as Usnea and Cladonia, can be used to make medications.
Lobaria pulmonaria, for example, is used in the tanning of leather.
Some lichens, such as Usnea, are utilised in brewing.

Types of Lichens

Lichens can grow in one of the following ways.

Crustose disperses throughout the substrate.
Foliose tissue sheets are flat, leaf-like, and loosely attached tissue sheets.
Squamulose are tightly clustered light flattened pebble units.
Fruticose are easily accessible upright branching tubes.

Despite differences in fundamental development, lichens have the same interior architecture. The lichen’s layers are defined by the relative density of the fungal partner’s filaments, which make up the majority of the lichen’s body.

The filaments are closely packed together at the outer surface to form a cortex, which aids in environmental interaction.

The algal companion cells are not spread below the cortex because the fungal filaments are dispersed. Underneath the algal layer, which is made up of loosely woven fungal filaments, is the medulla. There is another layer under the medulla in foliose lichens, which is in direct contact with the underlying substrate in squamulose and crustose lichens.

Lichen Internal Structure

The mycobiont makes up the majority of the lichen’s body, with the phycobiont accounting for only 5%.
The top cortex, algal zone (gonidial layer), middle medulla, lower cortex, and rhizines are the different parts of the body.
Photosynthetic partners are only found in the algal zone.
Ascomycetes is the fungus companion in roughly 98 percent of lichens. Basidiomycetes and Deuteromycetes are the fungus partners in the remaining cases.

Conclusion

A lichen, rather than being a single creature, is a symbiosis of various species such as fungus and cyanobacteria or algae. Cyanobacteria are commonly referred to as blue-green algae, despite the fact that they are not algae. A few lichens exhibit filamentous formations among photobionts, whereas others are formed up of chains of more or fewer cells. Ascomycetes or Basidiomycetes species are the most common fungus in lichens.