General Characteristics of Lichen
What are lichens?
Lichens are structurally organized permanent symbiotic association between fungi and algae. The fungal component of lichen is called mycobiont and the algal component of lichen is called phycobiont. Theophrastus (371 – 284 BC), who is known as the ‘Father of Botany’, for the first time used the term lichen to denote the superficial growth on tree barks.
The branch of biology which deals with the study of lichen is called Lichenology and the one who studies is known as lichenologist. Acharius is known as the ‘Father of lichenology’.
Lichens are symbionts:
Lichens are symbiotic association between algae and fungi. The term Symbiosis (introduced by De-Bary, a mycologist) is used to specify the association or interaction of organisms where both partners are mutually benefitted. The fungus absorbs water and protects algae from unfavorable conditions such as drought and extreme temperature. The algal components, since they are autotrophs, in turn supplies organic food to fungus. This type of symbiosis is known as heliotism, a ‘master’ and ‘slave’ relationship.
Lichens do not show the morphology of fungi and algae:
Even though lichens are symbiotic association between algae and fungi, the vegetative morphology (plant body) of lichen neither resembles algal or fungal morphology. Fungal component is prominent vegetative part in lichen than algal component. Almost 90% of the plant body of lichen composed of fungal component. Due to the ill differentiated plant body, lichens are included in Thallophyta of Cryptogams along with algae and fungi.