The two main types of mycorrhizas are ecto and endomycorrhizas, which differ in their structure and physiological relationships with host plant. Mycorrhizal fungi frequently stimulate plants to reduce root biomass while simultaneously expanding nutrient uptake capacity by extending far beyond root surfaces and proliferating in soil pores that are too small for root hairs to enter. Legume roots are invaded and colonized by rhizobia and also with mycorrhizal fungi. For legumes, arbuscular mycorrhizal (AM) fungi have fundamental effects on the eco-physiology, on the biota of the surrounding soil and on associated non-legumes. AM-fungi are known to be effective in increasing nutrient uptake, particularly phosphorus and biomass accumulation of many crops in low phosphorus soil. AM-fungi have an important role in promotion of biological and chemical properties of plants under stressed environment. Most reports note a positive effect of mycorrhizal inoculation on growth of plants in metal- contaminated soils.
