What is a lichen?

Lichens are not a single organism, in fact they are an associated organism or symbiosis between two different organisms. Those two contributing organisms are a fungus and an alga or cyanobacterium (also known as blue-green algae) which live together in a new form known as a thallus.

The basic fungal and algal components live together in a symbiotic association. The fungus is called the 'mycobiont' and one or more algae and/or a cyanobacteria is called the 'photobiont'. It is the algae 'photobiont' that has chlorophyll and can photosynthesize, so providing carbohydrates for both itself and its fungal partner.

The lichen body or thallus is made up of a tangle of fungal filaments called hyphae which clasp the algae, either in a mat or wrapped as single cells. It is the fungal partner that provides a sheltered environment for the alga, protecting it to some extent from the elements and providing mineral nutrients and collecting water. In some species the fungi extracts minerals from substrates for both organisms. 

Lichens are named after the fungal partner in the symbiosis.

Further reading

What is a lichen - British Lichen Society

Lichens - Wikipedia

Australian National Botanic Gardens - What is a lichen?




This page last updated on 10 Oct 2015