A hydroponic experiment was conducted to investigate the effects of oxalic acid (OA) on arsenic (As) uptake and the physiological responses of Hydrilla verticillata exposed to 3 mg L-1 of As in different forms. Plant As(III) uptake was significantly increased by 200-2000 µg L-1 OA. However, an increase of As(V) uptake was only shown with 1000 µg L-1 OA, and no significant difference was observed with dimethylarsinate treatment. Peroxidase and catalase activities, and the contents of photosynthetic pigments, soluble sugar and proline, were significantly increased by 1000 µg L-1 OA during As(III) treatment. Superoxide dismutase and proline were also increased significantly by 1000 µg L-1 OA when plants were exposed to As(V). In DMA treatment, proline was significantly increased by 500 µg L-1 OA. Therefore, As-induced oxidative stress is relieved by OA, but it depends on OA concentration and the form of As. Our results may be useful for the phytoremediation of waste water containing As and OA.
Keywords: Antioxidation; Arsenate; Arsenite; Black algae; Dimethylarsinate; Organic acid.