Root Exudates and Their Roles in Phytoremediation

Abstract

In general, root exudates can affect metal absorption by plants through changing the physical and chemical characters of rhizospheres. The modes of root exudates in removing heavy metals vary in a broad range, for example, by modifying the pH of the rhizosphere, chelating, complexting and depositing with heavy metals, altering the numbers and the activity of rhizospheric microbes. Through these ways, root exudates can change the chemical existence of heavy metals, increase their bio-availability, activate soil microbes and reduce the environmental dangers. While removing organic contaminants in the soil, the ecotoenzymes in the root exudates may degrade pollutants directly, or degrade them indirectly by stimulating the activity ofo rhizospheric microbes (which is considered to be the dominant process). Root exudates do play a key role in phytoremediation on contaminated sites. Future research should focus on seeking and screening certain specific plants with high bioproduction and excellent efficacy, especially developing hyper-accumulators, and testing their efficiency in removing heavy metals or organic pollutants by lab and/or field trials. Emphasis should also be laid on process-oriented correlations between contaminants and root exudates of these palnts. If so, more effective approaches to ecological restoration of polluted soils can be developed and put into practice.