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A lichen (/ ˈ l aɪ k ən / LIE-kən, UK also / ˈ l ɪ tʃ ən / LI-chən) is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungi species, along with yeasts and bacteria [1] [2] embedded in the cortex or "skin", in a mutualistic relationship.
One reason the greenshield lichen can be more commonly found than other lichen species is because it is relatively tolerant of pollution. Lichens are often used to monitor air quality.
Lichens are symbiotic organisms that play an important role in the biogeochemical cycle on Earth. The characteristics of lichens, such as strong resistance to factors such as desiccation, ability to grow and break down rocks allow lichen to grow in different types of environment including highly nitrogen limited area such as subarctic heath.
A cyanolichen is a lichen with a cyanobacterium as its main photosynthetic component . [12] Many cyanolichens are small and black, and have limestone as the substrate. Another cyanolichen group, the jelly lichens (e.g., from the genera Collema or Leptogium) are large and foliose (e.g., species of Peltigera, Lobaria, and Degelia. These lichen ...
Lichens are known in which there is one fungus associated with two or even three algal species. Rarely, the reverse can occur, and two or more fungal species can interact to form the same lichen. [12] Both the lichen and the fungus partner bear the same scientific name, and the lichens are being integrated into the classification schemes for fungi.
Some lichens live a long time; one species has been dated at 8,600 years. [126] However their lifespan is difficult to measure because what defines the same lichen is not precise. [ 127 ] Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the same lichen, and two lichens of different ages can merge, raising ...
Although there are many lichen species throughout the world, only a few species of lichen are known to be both edible and provide any nutrition. [6] Two problems often encountered with eating lichens is that they usually contain mildly toxic secondary compounds, and that lichen polysaccharides are generally indigestible to humans. Many human ...
Fruticose or ‘shrubby’ lichens differ from other forms of lichen because their bushy form is attached to the substrate only at the base of the lichen. A continuous algal layer grows around the circumference of the branches of the lichen. [3] Many fruticose lichens have fine, round, hair-like structures and are loosely attached to rocks and ...