Differential generation of hydrogen peroxide upon exposure to zinc and cadmium in the hyperaccumulating plant specie (Sedum alfredii Hance)

摘要

Sedum alfredii Hance has been identified as zinc (Zn) and cadmium (Cd) co-hyperaccumulator. In this paper the relationships of Zn or Cd hyperaccumulation to the generation and the role of H(2)O(2) in Sedum alfredii H. were examined. The results show that Zn and Cd contents in the shoots of Sedum alfredii H. treated with 1000 mumol/L Zn(2+) and/or 200 mumol/L Cd(2+) increased linearly within 15 d. Contents of total S, glutathione (GSH) and H(2)O(2) in shoots also increased within 15 d, and then decreased. Total S and GSH contents in shoots were higher under Cd(2+) treatment than under Zn(2+) treatment. However, reverse trends of H(2)O(2) content in shoots were obtained, in which much higher H(2)O(2) content was observed in Zn(2+)-treated shoots than in Cd(2+)-treated shoots. Similarly, the microscopic imaging of H(2)O(2) accumulation in leaves using H(2)O(2) probe technique showed that much higher H(2)O(2) accumulation was observed in the Zn(2+)-treated leaf than in the Cd(2+)-treated one. These results suggest that there are different responses in the generation of H(2)O(2) upon exposure to Zn(2+) and Cd(2+) for the hyperaccumulator Sedum alfredii H. And this is the first report that the generation of H(2)O(2) may play an important role in Zn hyperaccumulation in the leaves. Our results also imply that GSH may play an important role in the detoxification of dissociated Zn/Cd and the generation of H(2)O(2).