Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2001
Publication Date: November 22, 2001
Numerous reports have suggested that soil bacteria and fungi may affect metal uptake by hyperaccumulators. If true, it may be possible to manipulate the soil environment so that metal uptake is increased and the process of phytoremediation is enhanced. In particular, it has been suggested that arbuscular mycorrhizae are very important in the uptake of metals into hyperaccumulators. However, this is not generally true because many hyperaccumulators belong to plant families that are not colonized by arbuscular mycorrhizae. Of those few hyperaccumulators that are mycorrhizal, there is no published work we are aware of that has examined this relationship. Numerous publications exist showing that bacteria affect metal uptake into crop plants, thus affecting the metal tolerance of plants and safety of plant-foods. Mechanisms whereby soil microbes may affect metal tolerance or uptake are reviewed for Ni, Zn, Pb, Hg, Se, and other elements. No direct evidence that soil microbes affect Ni uptake by likely phytomining plants has been obtained. However, improved phosphate status of mycorrhizal plants reduced shoot Pb concentrations, and prevention of the mycorrhizal infection with the fungicide benomyl increased shoot Pb in corn. We tested the metal tolerance of rhizosphere microbes of Thlaspi caerulescens and red clover, finding that the Thlaspi rhizosphere microbes had increased Zn and Cd tolerance, presumably due to increased metal availability in their rhizosphere. The present state of our knowledge on these issues will be summarized.