Photosynthetic activity and antioxidative response of seagrass Thalassia hemprichii to trace metal stress

This study concerned the accumulation of trace metals in tissues of seagrass（Thalassia hemprichii） exposed to various concentrations of Zn2＋,Cd2＋,Pb2＋and Cu2＋for 10 d,and the effect of excessive metals on quantum yield（ΔF/Fm）,photosynthetic pigments and antioxidative enzymes like superoxide dismutase（SOD）,guaiacol peroxidase（POD） were also examined.Cadmium was the most highly accumulated metal.Meanwhile,high metals levels led to a remarkable breakdown of photosynthetic parameters.Especially,ΔF/Fm,chlorophyll and carotenoid were significantly low during prolonged Cu exposure.Besides,ΔF/Fm was more severely depressed by Cu and Zn than Pb and Cd.However,T.hemprichii had positive response by increasing the activity of SOD and POD.The results indicate that T.hemprichii is the most sensitive to Cu,and the antioxidative protection mechanisms of T.hemprichii are more efficiently activated to avoid damage of Zn,Cd and Pb stress.Finally,due to the high Cd-accumulation and strong Cd-tolerance capacity,T.hemprichii can be used for phytoremediation in Cd-contaminated areas.