What is Lichen and how is it used as an indicator?

Answer 1

they are rootless plants, and the source of litmas paper tests.

Litmus is a water-soluble dye extracted from certain lichens, especially Roccella tinctoria, and absorbed on to filter paper. The resulting piece of paper becomes a pH indicator (one of the oldest), used to test materials for acidity. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic (i.e. alkaline) conditions, the colour change occurring over the pH range 4.5-8.3 (at 25°C). Neutral litmus paper is purple in colour. The active ingredient of litmus is called azolitmin.

Lichens doinate about 8% of the earth's surface. There are about 30,000 species known in the world and between five and ten new lichens are discovered in the UK each year. They are important to people because they are part of the nitrogen, phosphorus and sulphur cycles and they are also vital in the early stages of soil formation.

Answer 2

Lichens are mutualistic associations between a fungus and a photosynthetic organisms, either cyanobacteria or green algae. They live on bare rocks and on the trunks of tree and get their moisture from the air. They are, therefore, very sensitive indicators of air quality. Decreases in lichen densities in a given area are indicative of a drop in air quality.

Answer 3

lichens are a symbiotic collection or association of millions of photosynthetic microorganisms held in a mass of fungal hyphae. They are an indicator of air quality. They are sensitive to sulfur dioxide and other aerial poisons.

Answer 4

Lichen is dry looking plant that grows on rocks

Answer 5

lichens are the symbioses of funges and algaes. The funges "pick up" water and other stuffs that are important for life, and give it to the algaes, and they make food.
This living creature is really sensitive to the impurities of the air (e.g.: SO2)
(sorry that this explanation was unscientific bt i'm not english)

Answer 6

http://en.wikipedia.org/wiki/Lichen

http://www.lichen.com/