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 μM 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 O2−. 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 μM 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 μM Pb2+ and decreased thereafter. The Pb uptake and accumulation mechanism were discussed.

► Vallisneria natans can be considered as a Pb hyperaccumulator.
► Pb-induced increases of H2O2 and O2− levels were detected in vivo.
► The antioxidant responses were actively regulated by V. natans under Pb stress.