Role of arbuscular mycorrhizal fungi in alleviation of Zn phytotoxicity and mineral nutrition of host plants

There is increasing interest worldwide in the maintenance of soil quality and remediation strategies for management of soils contaminated with pollutants including heavy metals. The protective effects of arbuscular mycorrhizas on host plants under conditions of Zn contamination have raised the prospect of utilizing the mutualistic association in soil revegetation programmes, and consequently research has focused on the mechanisms involved. This paper summarizes some of our recent research work which has indicated that the alleviation of zinc toxicity by arbuscular mycorrhiza may involve both direct and indirect mechanisms. Binding of metals in mycorrhizal structures and immobilization of metals in the mycorrhizosphere may have contributed to the direct effects. Indirect effects may include the mycorrhizal contribution to balanced plant mineral nutrition, especially P nutrition, leading to increased plant growth and enhanced metal tolerance. Further research on the potential application of arbuscular mycorrhizas in the bioremediation of metal contaminated soils is also discussed.