The Research Progresses on Mitigative Mechanism of Silicon on Heavy Metal Toxicity in Plant

Silicon plays en effective role in mitigating heavy metal stress. It has been reported that, appropriate concentration of exogenous silicon can alleviate the damage of heavy metal on plant growth by affecting the change of enrichment coefficient and translation coefficient of heavy metals, reducing the absorption and accumulation of heavy metal in plant, effectively mitigating the damage on plant cell and promoting physiological and biochemical metabolism of plant. The mechanism can be concluded as avoidance and tolerance. Avoidance includes improving the pH of growth media, changing its physicochemical properties, changing the forms of heavy metal and deposited in soil and decreasing the absorption of heavy metal. Tolerance includes affecting heavy metal transportation and accumulation in plant, stimulating production of phenolics, chelating with heavy metal, promoting compartmentalization of heavy metal ion in plant, causing it bounded in cell wall or vacuole, improving the activity of antioxidant system, such as SOD, POD, CAT and APX, and effectively removing active oxygen caused by heavy metal stress. In this paper, the effect and mechanism of silicon on heavy metal toxicity were summarized and induced, and on these bases, key research directions in future were prospected.