[Root excretion and plant resistance to metal toxicity]

Reducing the availability and toxicity of metal pollutants before they enter plant body is one of the main mechanisms of plant resistance to metals. Root system is the first entrance of metal pollutants from soil into plant. It can excrete organic acids, amino acids, sugars, growth substances etc. into rhizosphere. Root excretion affects the metal absorption by plant through changing the physical and chemical characters(such as pH, Eh) of rhizosphere. The metal pollutants are detained outside the roots by chelation, complexation and disposition with root exudates. The quantity and activity of metals in rhizosphere are changed by root exudates through changing the composition, activity and excretion of microbes there. After reviewing the research advances on root excretion and plant resistance to metals, the authors pointed out the existing problems and the major topics and significance of further research.