2. Definition
Lichens are slow growing, long living organism formed by
the symbiotic association between algae and fungi that form
a unique morphology distinct from both partner.
•The fungal partner is called mycobiont
•The algal partner is called phycobiont Theophrastus coined
the term ‘lichen’ for superficial growth on the bark of olive
tree.
About 500 genera and over 15000 species are known Lichen
3.
4. Features of Lichens
Grows in areas where either fungi or algae could not survive alone: rocks,
cement, rooftops, trees, and newly exposed soil.
world wide distribution and can grow in the extremes of temperature and heat
Grows very slowly, secreting acids that break down rocks.
Accumulate nutrients needed for plant growth.
Thallophytic plant body, irregularly shaped and often deeply pigmented
Colouration is due to the pigmentation of the alga partner .
6. Classification of Lichen
There are two groups of lichens. They are classified on
the nature and kinds of fruit bodies of the fungal partner.
1. Ascolichen:
The fungal member of this lichen belongs to
Ascomycotina.Most of the lichen belong to this group.
2. Basidiolichen:
The fungal member of this lichen belongs to
Basidiomycotina e.g., Dictyonema, Corella.
7. Morphological class of Lichen
Lichens occur in one four basic growth forms
1.fruticose – free standing branching tube, branches
cylindrical to ribbon like in form. E.g. usinia
2.foliose – with flat sheets of tissue not tightly bound,
leaf-like lobes. E.g. physcia
3.crustose– crust-like, adhering tightly to a surface
(substrate) like a thick coat of paint. E.g. graphis
4.squamulose – formed of small leaf-like scales crustose
below but free at the tips
10. Special Features of Lichen
Caloplaca obamae is a species of lichen in the fungus
genus Caloplaca. It is the first species to be named in
honor of United States President Barack Obama.
C. obamae was discovered in 2007 by Kerry Knudsen
on Santa Rosa Island in California and published in
March 2009. Knudsen states that he chose to honor
Obama for "his support of science and scientific
education" and wrote the manuscript for publication of
the species in the time between Obama's election and
his inauguration.
• Caloplaca obamae looks like moss or dry leaf.
11. Importance Of Lichens
• Early colonizers in barren dry and naked rocks, cliffs, mountains and new terrains.
• It paves the way for the growth of mosses and grasses.
• Staple food for many animals in tundra region.
• Used as biological stain.
• Source for litmus paper which is used as pH indicator.
• Used in in making perfumes.
• Used for the preparation of ointment for the treatment of burns and wounds.
•Lobaria pulmonare for lung diseases
• Decrease in lichens in an area is indicative of air pollution especially Sulphur dioxide pollution.
