Lichen
Lichens are composite organisms formed by a symbiotic association between a fungus and a photosynthetic partner, usually a green alga or cyanobacterium.
Lichens are composite organisms formed by a symbiotic association between a fungus and a photosynthetic partner, usually a green alga or cyanobacterium. They are not plants, but have plant-like forms and live in many terrestrial habitats worldwide. The fungal partner makes up most of the lichen body and provides structure, while the photosynthetic partner supplies sugars through photosynthesis.
Biology
A lichen is a stable symbiosis between a fungus (mycobiont) and one or more photosynthetic partners (photobionts), which can be green algae, cyanobacteria, or both. The fungus forms most of the structure, while the photobiont provides carbohydrates from photosynthesis.
Structure and forms
The lichen body is called a thallus and is organized differently from plant tissues. Fungal hyphae surround the photobiont cells. Common growth forms include crustose, foliose, and fruticose lichens.
Ecology and habitat
Lichens can live on rocks, bark, soil, and other exposed surfaces, and they are found in many terrestrial habitats worldwide. They obtain water and nutrients directly from rain and air rather than through roots or vascular tissue. In Canada, lichens are widespread across forests, tundra, boreal regions, and rocky habitats, and they are often used in ecological monitoring because many species are sensitive to air quality.
Reproduction
Lichens reproduce in several ways. The fungal partner can reproduce sexually by producing spores. Some lichens also spread vegetatively when both partners disperse together.
Key facts
- Lichens are mutualistic associations, not single organisms.
- The fungal partner is called the mycobiont and the photosynthetic partner the photobiont.
- Lichens absorb water and nutrients directly from the environment rather than through roots or vascular tissue.
- Lichens reproduce both sexually, through fungal spores, and vegetatively, when both partners disperse together.
Lichens are widespread across Canada, especially in forests, tundra, boreal regions, and rocky habitats, and they are often used in ecological monitoring because many species are sensitive to air quality.
Frequently asked questions
What is a lichen?
Are lichens plants?
What do lichens eat?
Where do lichens grow?
How do lichens get water?
References
- Encyclopaedia Britannica — https://www.britannica.com/science/lichenSupports: Definition of lichens as symbiotic associations; worldwide distribution; approximate diversity.
- U.S. Forest Service — https://www.fs.usda.gov/wildflowers/beauty/lichens/about.shtmlSupports: Basic lichen biology; fungal dominance; lack of roots, stems, and leaves; water and nutrient absorption.
- U.S. Forest Service — https://www.fs.usda.gov/wildflowers/beauty/lichens/biology.shtmlSupports: Lichen structure, absence of vascular tissue, and environmental absorption of water and nutrients.
- U.S. Fish & Wildlife Service — https://www.fws.gov/story/2023-12/lichen-what-fungus-itSupports: Composite organism explanation; photobiont role; fungi-algae/cyanobacteria partnership.
- British Lichen Society — https://www.britishlichensociety.org.uk/learning/what-is-a-lichenSupports: Symbiotic association; photobionts; mutualism; multiple partners in some lichens.
- British Lichen Society — https://www.britishlichensociety.org.uk/learning/lichen-biologySupports: Reproduction by fungal spores and vegetative dispersal.