Is lichen parastic or saprophytic?

Question

Saprophytic = feeds on dead host
Parasitic = feeds on living host

Lichen feeds on live trees (parasitic) and rocks which are inanimate (saprophytic)

Is there a third category for both?

Answer 1

Lichens are symbiotic associations of a fungus with a photosynthetic partner (called a photobiont or phycobiont) that can produce food for the lichen from sunlight. The photobiont is usually either a green alga or a blue-green alga (cyanobacterium). A few lichens are known to contain yellow-green algae or, in one case, a brown alga. Some lichens contain both green and blue-green algae as photobionts; in these cases, the blue-green (cyanobacterial) symbiont component may specialize in fixing atmospheric nitrogen for metabolic use.

The body (thallus) of most lichens is quite different from that of either the fungus or alga growing separately, and may strikingly resemble simple plants in form and growth (Sanders 2001). The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations; however, the algal cells are never enclosed inside the fungal cells themselves (The fungus Geosiphon pyriforme is unique in that it encloses a cyanobacterial symbiont inside its cells, but this exceptional association is not usually considered to be a lichen.) The fungus may or may not penetrate into the algal cells with fine hyphal protrusions.

In general, the symbiosis is considered obligatory for successful growth and reproduction of the fungus; however, the significance for the algal symbiont is less clear. For some algae, the symbiosis may be obligatory for survival in a particular habitat; in other cases, the symbiosis might not be advantageous for the alga. Thus, there is some controversy as to whether the lichen symbiosis should be considered mutualistic or parasitic. Nonetheless, the lichen is typically a highly stable association which probably extends the ecological range of both partners.

There is evidence that lichens might involve a controlled form of parasitism of the algal cells. In laboratory settings, cyanobacteria grow faster when they are alone rather than when they are part of a lichen. But there is also a mutualistic side to the relationship, the fungus part of the lichen provides the alga with water and minerals that the fungus absorbs from whatever the lichen is growing on. As for the alga, it uses the minerals and water to make food for the fungus and itself. Lichens take the external shape of the fungal partner and hence are named based on the fungus. The fungus most commonly forms the majority of a lichen's bulk, though in filamentous and gelatinous lichens this may not always be the case. The lichen fungus is typically a member of the Ascomycota—rarely a member of the Basidiomycota. Formerly, some lichen taxonomists placed lichens in their own division, the Mycophycophyta, but this practice is no longer accepted because the components belong to separate lineages.

The algal or cyanobacterial cells are photosynthetic, and as in higher plants they reduce atmospheric carbon dioxide into organic carbon sugars to feed both symbionts. Both partners gain water and mineral nutrients mainly from the atmosphere through rain and dust. The fungal partner protects the alga by retaining water, serving as a larger capture area for mineral nutrients and, in some cases, provides minerals obtained from the substratum. If a cyanobacterium is present, as a primary partner or another symbiont in addition to green alga as in certain tripartite lichens, they can fix atmospheric nitrogen, complementing the activities of the green alga.

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Answer 2

Lichens are found throughout the world, often occupying areas where no other plant can become established. They are found in their greatest numbers in the Alpine and Arctic regions, where they are the dominant form of vegetation. Lichens are the products of two distinct groups of plants. Together fungi and algae (seaweed is an algae) combine to produce lichens. Most rocks you will come across have an abundance of these plants. Lichens are almost the only plants able to survive the severe conditions at high altitudes. In Antarctica, where there are very few flowering plants, more than 400 species have been found. In warmer climates lichens are common in old fields and forests, on rotting logs and on tree trunks. However, few species survive near large cities. Unfortunately, lichens are very sensitive to industrial smoke and gases.

Answer 3

Lichen doesn't feed on trees or rocks at all, that's just where it sits. It's a symbiotic arrangement between fungus and algae or cyanobacteria. The fungus gets carbohydrates from its partner and the algae/cyanobacteria get protection from the elements through its fungus covering.
Lichens that contain cyanobacteria are actually good for trees, since they fix nitrogen from the air. Then when lichens die, or it rains, that nitrogen fertilizes the trees.

Answer 4

no .living and non living to know if lichen grows in your area this means it is pollution free place .and lichen is very useful for us;in certain ways and some how not.

Answer 5

There is evidence to suggest that the lichen symbiosis is parasitic rather than mutualistic (Ahmadjian 1993).