Understanding molecular mechanisms for improving phytoremediation of heavy metal-contaminated soils

Abstract

Heavy metal pollution of soil is a significant environmental problem with a negative potential impact on human health and agriculture. Rhizosphere, as an important interface of soil and plants, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria or mycorrhizas have received more and more attention. In addition, some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals, and they manage to survive under metal stresses. High tolerance to heavy metal toxicity could rely either on reduced uptake or increased plant internal sequestration, which is manifested by an interaction between a genotype and its environment.A coordinated network of molecular processes provides plants with multiple metal-detoxifying mechanisms and repair capabilities. The growing application of molecular genetic technologies has led to an increased understanding of mechanisms of heavy metal tolerance/accumulation in plants and, subsequently, many transgenic plants with increased heavy metal resistance, as well as increased uptake of heavy metals, have been developed for the purpose of phytoremediation. This article reviews advantages, possible mechanisms, current status and future direction of phytoremediation for heavy-metal–contaminated soils.

Keywords::

• Soils
• heavy metals
• phytoremidiation
• eco-environmental improvement
• molecular mechanisms
• hyperaccumulator

Acknowledgments

Sincere thanks are given to two anonymous referees and Editor, Dr. Inge Russell for their critical comments and positive suggestions, respectively.

Declaration of interest

This work was jointly supported by 973 Program of China(2007CB106803), One hundred-Talent Plan of Chinese Academy of Sciences, the CAS/SAFEA International Partnership Program for Creative Research Teams, the Cooperative & Instructive Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau (10501-HZ), the Award Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Natural Science Foundation of Shanxi Province (No.20051034), Key Laboratory of Polluted Environment Remediation and Ecological Health,Ministry of Education, College of Natural Resources and Environmental Science, Zhejiang University, China(No. 050203), the Science & Technology Key Program of Shanxi Province (20090311072).