Effects of Pb on the oxidative stress and antioxidant response in a Pb bioaccumulator plant Vallisneria natans

The effects of Pb on photosynthetic pigments, oxidative stress and antioxidant response were assayed using biochemical and histochemical methods in leaves of Vallisneria natans (Lour.) Hara treated with 0-100 mu M Pb2+ for 0-6 d. The Pb content increased with the increase of exposure duration and a highest Pb uptake value (about 9.4 mg Pb g(-1) dry weight) was obtained at 6 d. Pb induced the accumulation of H2O2 and O-2(-). The increase of malondialdehyde content and the decrease of total chlorophyll and carotenoids were detected in V. natans under Pb stress. Activities of NAD(P)H oxidase, guaiacol peroxidase, glutathione reductase and ascorbate peroxidase increased at 75 mu M Pb2+ for 2-6 days, while activities of superoxide dismutase and catalase and the content of ascorbic acid increased within two days in plants exposed to 75 mu M Pb2+ and decreased thereafter. The Pb uptake and accumulation mechanism were discussed. (C) 2011 Elsevier Inc. All rights reserved.