Overview of Lichens Course name- B.Sc. Part- I Botany

DR. VISHNUPRIYA SHARMA What are Lichens

Lichens are distinct group of plants and the plant body consist of permanent association of fungal and algal component living together in a intimate symbiotic relationship. The algal component is called as phycobiont ( phykes = algae, bios=life) and the fungal component is called as mycobiont( mykes = fungus). Lichens have a specific structure which neither resembles fungi or algae and they are self supporting living entity.

History of Lichens

Term lichen is traced back in 371- 28 BC in literature described by Theophrastus in History of plants .Lichen is a word of greek origin which means any superficial growth on the bark of trees. The one who studies the lichens is known as lichenologist Earlier workers like Dioscorides, Wallorth and Schwendener need a special mention in the field of lichenology( study of lichens).

Distribution of Lichens

The distribution of lichens is controlled by the climate and substratum. They grow in the presence of good amount of moisture, cold or moderate temperature and pure atmosphere. They grow luxuriantly in tropical and subtropical rain forest due to abundance of moisture. Lichens are found in abundance in eastern Himalayan region of India. Kinds( types) of Lichens- Lichens can be categorized on following basis:-

A. ON THE BASIS OF B. ON THE BASIS OF HABITAT OR C. ON THE BASIS OF EXTERNAL MYCOBIONT- ECOLOGY MORPHOLOGY lichens can be categorized in lichens can be categorized in 3 lichens can be categorized in 3 two kinds : 1 .Ascolichen and 2. types as follows types as follows Basidiolichen 1. Arboreal – they grow on bark 1. Crustose lichen 2. Foliose Fugal component belonging to or wood, leaves lichen 3. Fruticose lichen ascomycotina are referred as 2. Terricolous- grows on ground Ascolichens and if fungal component is a member of 3. Saxicolous- grows on rock Basidiomycotina then it is referred as Basidiolichen

1. Crustose lichen

Encrusting ,thin and firm texture. Very closely attached to the substratum. Thallus remain partly imbedded or completely embedded inside the surface on which it grows. In those lichens where thallus is completely embedded inside the substratum only ascocarps of the fungus which are the fruiting bodies are present on the surface. 2. Foliose lichen

Leaf like thallus having lobed or irregular margins, looks like dried liverworts. The plant body is attached to the substratum by means of branched hyphal system called as rhizines.

3 Fruticose lichen

These have branched and bushy or shrubby upright structure. They may be erect (Cladonia) or pendent (Usnea). The plant body remain attached to the substratum by means of a mucilaginous disc. Internal structure

Internal structure of lichens is a complex consortium between algae and fungi Only in the advanced foliose forms four distinct regions can be seen in the vertical section of thallus 4 zones are 1. upper cortex 2. algal layer 3. medulla 4. lower cortex Reproduction 1.asexual 2.sexual

Asexual Reproduction 1. By fragmentation 2. By soredium 3. By cephalopodium 4. By isidium Sexual reproduction

In lichens the sexual reproduction is performed by the fungal partner which generally belongs to ascomycotina Sexual reproduction is similar to that of ascomycotina Economic importance of Lichens

As food and fodder As medicines As dyes In tanning industry In cosmetics and perfumery Ecological importance- They are pioneer of succession and indicators of pollution References and Acknowledgement

 College botany Vol 1 by- B P Pandey (for diagrams)  Special thanks for Ms.Justyna Malec for taking various photos of lichens in natural habitat at wojcechowka, Tyszowce Poland in month of september 2017 and sharing them in this presentation