Arbuscular mycorrhizal fungi and heavy metal tolerance in plants

Abstract

Arbuscular mycorrhizal (AM) fungi are soil fungi developing symbiotic association with most terrestrial plants. In such a symbiosis, the fungi provide the host plant with water and nutrients in exchange for carbon. The beneficial effects of AM fungi on the growth of the host plant under stresses such as salinity, drought, heavy metals, etc. have been indicated by research work. However, more has yet to be elucidated on the mechanisms, which may increase the host plant as well as the fungal tolerance under stress. The alleviating effects of the fungi on plant growth and the environment under stress are mostly due to the superb abilities of the fungi in developing physiological and morphological mechanisms. The stress of heavy metals is among the most important stresses adversely affecting plant growth and the environment. The use of biological methods including the use of soil microbes such as AM fungi, plant growth-promoting rhizobacteria (PGPR), and endophytic bacteria has been proved to be among the most effective ones alleviating the adverse effects of stress on plant growth and the environment. The details of bioremediation mechanisms used by the fungi in association with the host plant including the expression of stress genes, the production of glomalin, the fungal phylogeny, and the allocation of heavy metals to different parts of mycorrhizal plant under the stress of heavy metals and some of the most recent advancement in this respect are presented in this chapter.