MYCORRHIZA (FUNGAL ROOTS) | Structure & its Benefits
The mutual beneficial or symbiotic association of a fungus with roots of higher plants (gymnosperms and angiosperms) represents mycorrhiza.
|Benefits to fungi||Benefits to plant|
|1. Nourishment from root cortical cells.
|1. Surface area for absorption increases.
2. Enhanced supply of H,O, N, P,S.
The mutually beneficial or symbiotic association of a fungus with the roots of higher plants is termed mycorrhiza. Mycorrhizal roots differ in shape from normal roots and often show a wooly covering. These roots lack root cap and root hairs. A fungus may get associated with roots of a number of plants and a particular plant may form association with a number of fungi. Depending upon the location of the fungus, the mycorhiza is of two types, .e., ectomycorrhiza and endomycorrhiza.
In ectomycorrhiza, the fungal hyphae are mainly external, forming a wooly covering on external surface of root and forms network of mycelium (Hartig net) in the intercellular spaces of the cortex. Fungal partner is commonly basidiomycetes like Boletus, e.g., Pinus roots
In endomycorrhiza, the fungal hyphae enter the tissue of the root, spreading intercellularlly and intracellularly. The fungus is able to break the cell wall in a limited way and is restricted to cortical region of the root. Some hyphae send small projections into cortical cells without destroying them. Such fungi are termed VAM (Vesicular Arbuscular Mycorrhiza), e.g., Orchid roots.
Mycorrhizal association is a symbiotic relationship as both the partners are mutually beneficial to each other. The fungal partner obtains nourishment from the cortical cells of the root and depends upon the plant for shelter. The root cells excrete sugars and other soluble gradients which are used by fungal hyphae spreading in intercellular spaces. The hyphae may get nourishment from the cells directly and also by sending small projections into cortical cells. The fungus seems to be essential for the growth of the plant having mycorrhiza. The plant also gets benefit from the association as the fungal hyphae spreading in soil substantially increases the surface area of absorption, thereby enabling the plant to get enhanced supply of water, nitrogen, phosphorus and other minerals from the soil. Orchids seldom occur without mycorrhiza. Certain forest trees like pines, birches show stunted growth if their roots are not associated with fungus.