Question

what is lichen? write it's characteristics?​

Answer 1

Answer:

Characteristics. A lichen is a combination of two organisms, a green alga or cyanobacterium and an ascomycete fungus, living in a symbiotic relationship.

Answer 2

Answer:

Lichens are a small group of plants of composite nature, consisting of two dissimilar organisms, an alga-phycobiont (phycos — alga; bios — life) and a fungus-mycobiont (mykes — fungus; bios — life); living in a symbiotic asso­ciation.

1. Lichens are a group of plants of composite thalloid nature, formed by the association of algae and fungi.

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2. The algal partner-produced carbohydrate through photosynthesis is utilised by both of them and the fungal partner serves the func­tion of absorption and retention of water.

3. Based on the morphological structure of thalli, they are of three types crustose, foliose and fruticose.

4. Lichen reproduces by all the three means – vegetative, asexual, and sexual.

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(a) Vegetative reproduction: It takes place by fragmentation, decaying of older parts, by soredia and isidia.

(b) Asexual reproduction: By the formation of oidia.

(c) Sexual reproduction: By the formation of ascospores or basidiospores. Only fungal component is involved in sexual reproduction.

5. Ascospores are produced in Ascolichen.

(a) The male sex organ is flask-shaped spermogonium, produces unicellular spermatia.

(b) The female sex organ is carpogonium (ascogonium), differentiates into basal coiled oogonium and elongated tricho­gyne.

(c) The fruit body may be apothecia! (disc­shaped) or perithecial (flask-shaped) type.

(d) Asci develop inside the fruit body con­taining 8 ascospores. After liberating from the fruit body, the ascospores ger­minate and, in contact with suitable algae, they form new lichen.

6. Basidiospores are produced in Basidiolichen, generally look like bracket fungi and basidiospores are produced towards the lower side of the fruit body.

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7. The growth of lichen is very slow, they can survive in adverse conditions with high temperature and dry condition.