Lichen and Mycorrhiza MCQ - Practice Questions with Answers

Lichen 

• A lichen is a symbiotic association between algae and fungi.
• The algal component is called phycobiont and it provides food to the fungal component.
• The fungal component is called mycobiont and it provides shelter and protection to the algal part.
• Lichens grow in a variety of areas like barren rocks, moist habitats, tree bark, window panes etc.
• Lichens are of following types:
• 1. Crustose- crust like e.g. Graphis, Rhizocarpon etc.
• 2. Foliose- The body of a lichen is leaflike, flat, broad, lobed and leaf-like. E.g. Parmelia.
• 3. Fruticose- Branched like a bush. e.g Usnea, Cladonia
• 4. Squamulose - tightly clustered and slightly flattened pebble-like units.
• Lichens are good pollution indicators.
• Lichen such as Rocella tinctoria is used to obtain biological stain orcein and it is also a source of litmus.

Mycorrhiza

• Mycorrhiza refers to the symbiotic association of fungi with the roots of higher plants. The fungus is dependent upon the higher plants for shelter and food. The fungus helps the roots in the absorption of water and phosphorus from soil.
• Mycorrhizae are of three types:

1. Ectomycorrhiza:  Fungus lies on the surface of the root. Only a little part of it penetrates intercellular spaces of the cortex. Ectomycorrhiza is less common.
2. Endomycorrhiza: Fungus lies inside the cortex of root. Some hyphae may penetrate the cortical cells also. Endomycorrhiza is more common (80% of plant families). 
3. Vesicular-arbuscular mycorrhiza: The fungus colonizes the root cortex forming a mycelial network and characteristic vesicles (bladder-like structures) and arbuscules (branched finger-like hyphae).