Effects of Cu~(2+),Cd~(2+),Hg~(2+) on the Antioxidant Enzyme Activities of Rice Seedlings

Objective:In order to investigate rice resistance mechanisms to different types of heavy metal ion,the effects of Cu2+,Cd2+,Hg2+ on several physiological indexes of rice seedling were studied.Method:The rice seedlings were treated with Cd2+,Cu2+,Hg2+ with different concentration including 0 mmol/L,0.25 mmol/L,0.5 mmol/L,1.0 mmol/L,the length of root and leaf,the contents of chlorophyll and protein,the activities of catalase,superoxide dismutase and peroxidase,and the changes of isoenzyme expression were measured.Result:The growth of rice seedlings was inhibited,soluble protein content in roots and leaves decreased,POD activity in root and leaves and SOD activity in root enhanced,treated by heavy metal ions.Cu2 + enhanced the SOD activity of leaves,however,Cd2 + decreased the SOD activity in leaves.Different concentrations of Cd2 + reduced the chlorophyll content in rice seedlings.Different concentrations of Hg2 + reduced the CAT activity in roots and leaves,Cd2+ enhanced the CAT activity of the root,but inhibit the CAT activity of leaves.With the increase of Cu2+ concentration,the CAT activity in roots and leaves gradually decreased.The electrophoresis of isozymes of POD and SOD were consistent with their activities.Conclusion: Cu2+,Cd2+ and Hg2+ have some effects on the activities of CAT,POD and SOD in rice seedlings.This effect was related with the type and concentration of heavy metals,and has organ specificity.Rice seedlings can increased or decreased antioxidant activity.So antioxidant system not only has detoxification function,but also was toxicity sites of Cu2+,Cd2+ and Hg2+ in plant.