- The term “mycorrhizae” refers to fungus associated with plant roots. Mycorrhizal fungi are the most researched group of beneficial fungi in science with over 15,000 publications on the subject. These are of two types:
- Ectomycorhiza: Ectomycorrhizal fungi are, economically, one of the most important groups of fungi. They are associated with trees such as pine, birch, hemlock, beech, spruce and fir. These fungi are stimulated by root exudates. The fungal hyphae forms a mantle both outside the root and within the root in the intercellular spaces of the epidermis and cortex. No intracellular penetration into epidermal or cortical cell occurs, but the extensive network called harting net is formed between these cells. The fungus then gains carbon and other essential organic substances from the tree and in return helps the trees take up water, mineral salts and metabolites. It can also fight off parasites, predators such as nematodes and soil pathogens.
2. Endomycorhiza (VAM): Endomycorrhizal fungi are microscopic and grow inside roots. Spores are formed in soil or roots. Then, they search the soil for nutrients, returning those to the plant. The plant, in turn, provides a home and carbohydrate for the mycorrhizae, forming a symbiotic association. They possess special structures known as vesicles and arbuscules. The arbuscules (small tree like, hyphal filled, invaginations of the cortical cells – which provide intimate contact between the plasmalemmae of the two symbiotic partners and are, presumably, the point of material exchange between host and fungus) help in the transfer of nutrients from the fungus to the root system. With the exception of species of Gigaspora and Scutellospora, the fungi form vesicles within the roots and the vesicles (lipid filled, terminal swellings of hyphae with a storage/perennating function) which are saclike structures, store P as phospholipids.