Arbuscular mycorrhiza can depress translocation of zinc to shoots of host plants in soils moderately polluted with zinc

There is increasing and widespread interest in the maintenance of soil quality and remediation strategies for management of soils contaminated with organic pollutants and trace metals or metalloids. There is also a growing body of evidence that arbuscular mycorrhizal (AM) fungi can exert protective effects on host plants under conditions of soil metal contamination. Research has focused on the mechanisms involved and has raised the prospect of utilizing the mutualistic association in soil re-vegetation programmes. In this short paper we briefly review this research, summarize some recent work and highlight some new data which indicate that the alleviation of metal phytotoxicity, particularly Zn toxicity, by arbuscular mycorrhiza may occur by both direct and indirect mechanisms. Binding of metals in mycorrhizal structures and immobilization of metals in the mycorrhizosphere may contribute 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 mycorrhiza in the bioremediation or management of metal-contaminated soils is also discussed.