Question

Why are mycorrhizae important?

Answer 1

Hint: A mycorrhiza is a mutual symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant's rhizosphere, its root system. In a mycorrhizal association, the fungal component colonizes the host plant's root tissues, it can be either intracellularly as in arbuscular mycorrhizal fungi (AMF or AM), or extracellularly as in ectomycorrhizal fungi. The association is sometimes mutualistic i.e. both the components depend on each other to an extent that in the absence of either of the components they can't survive. Sometimes mycorrhizae may have a parasitic association with host plants.

Complete answer:
About 95% of the world's plant species form mycorrhizal relationships with fungi and in most cases the plant would not survive without them.
The fossils study of the root of the plants suggests that mycorrhiza have existed from a very long time in plants. Scientists believe that plants were only able to move on to land when they had developed a mycorrhizal relationship with fungi.

Importance of fungi:
1. Increase nutrient uptake of plants from soil.e.g. N, K, Ca, Mg etc.
2. Mycorrhiza has a significant role in nutrient recycling.
3. Mycorrhiza are more tolerant to adverse soil chemical constraints which limit crop production, so mycorrhiza increases soil productivity.
4. It increases plant resistance to certain diseases and drought.
5. It helps in stimulating the growth of beneficial microorganisms.
6. It also improves soil structure, stabilizes soil aggregate – hyphal polysaccharides bind and aggregate soil particles.
7. It Increases absorption of certain nutrients like phosphate by crops and uptake of zinc also increases. Increases uptake of water from soil.
8. It also helps in increasing uptake of sulphur from the soil.
9.It also ncreases the concentration of cytokinins and chloroplast in plants which helps in protecting plants during stress conditions.
10.Plant hormones produced by fungus changes the physiological state of roots of plants.

Benefits to fungus:
1. Plants provide the source of Carbohydrates and energy. Sucrose from the plant is converted into trehalose and mannitol by fungus.
2. It is estimated that about 10% (or more) of photosynthate produced by trees is passed to mycorrhizae and other rhizosphere organisms.

Note:
Various studies have shown that tree growth is better when mycorrhizae are present as fungi increase the supply of inorganic nutrients to trees. Nowadays seedlings in nurseries are inoculated with fungi so that the plants have better chances of success. On anatomical and morphological basis, mycorrhiza are divided into 3 types- 1. Ectomycorrhizae 2. Endomycorrhizae 3. Ectendomycorrhiza.