What are lichens?

Lichens are organisms that grow on rocks, tree branches, and bare ground. They are a combination of two different organisms living together in a symbiotic relationship: a population of either algal (green) or cyanobacterial cells that are single or have filaments and fungi. Lichens do not have roots, stems, flowers, or leaves. The fungal component of a lichen is called the mycobiont (from the Greek terms mykes, which means “fungus,” and bios, meaning “life”), and the photosynthetic component is called the photobiont (from the Greek terms photo, meaning “light,” and bios, meaning “life”). The scientific name (genus/species) given to the lichens is the name of the fungus, which is most often an ascomycete (for more about this type of fungus, see this chapter).


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