What Are The Lichens?

Lichens are organism which shows association of fungus and algae. Fungal component is known as mycobiont and algae component is called phycobiont. Fungi can be ascomycetes or basidiomycetes. Algae are mainly Cyanobacteria. Theophrastus, the father of botany coined the term lichen. They often grow in adverse and difficult conditions. It includes barren rocks, roofs, walls, tree bark and leaves. However, they cannot bear air pollution and extreme desiccation conditions. They are sensitive to sulphur dioxide. They are of different colors and are perennial.

Explain the structural aspects of lichen planus?
Crustose, foliose and fruticose are different types of lichen planus. Crustose types of lichen have crust like appearance and are attached to the substratum at many places. Foliose are leaf like and are attached to substratum at one or two places. Fruticose are branched type and are attached to substratum by disc. Fungal partner is the dominant partner of lichen planus. It is divided into surface, the interior part (medulla) and attaching segments known as rhizines.

Explain the phenomena of symbiosis in lichen planus of Kingdom fungi?
Fungus provides structural aspect and covering of body. It also acts as an anchor and allows absorption of water and minerals. Algae are not the dominant segment in lichen planus. But they play an important role as they perform the process of photosynthesis. They also play a vital role in nitrogen fixation. The algae take water and other necessary materials from fungus to manufacture their food. The food which is manufactured passes on to fungus. So this association is of mutual benefit to algae and fungus. This is known as symbiosis. A sometimes fungus interferes in the function of algae. It acts as a controlled parasite. This is referred as holotism.

Explain the phenomena of reproduction in lichen planus of Kingdom fungi?

Lichen planus divides by various methods which are progressive death & decay, fragmentation, isidia and soredia. Progressive death and decay causes division of lichen into various parts. Fragmentation is caused by mechanical injuries like wind flow and animal bites etc. Isidia are outgrowths which are not real. These outgrowths increase the surface area and the rate of photosynthesis. They are made of algal cells which form core and periphery is made of fungal cells. So that’s why they can give rise to new lichen. Soredia are microscopic structures with are large in number present inside sori. These are dispersed by air currents. They are also combination of algae and fungal cells and give rise to new lichen.

Lichen act as an early colonizer on barren dry rocks, mountains and cliffs. They secrete acids and cause itching on rocks. It facilitates growth of grasses. They also act as a staple diet of some animals. They also play an important role for formation of perfume and dyes. They also act as an antibiotic. They also act as an indicator for air pollution. They cause forest fires and damage building by their acid formation which causes itching.

Category: Fungi

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