The effects of cadmium (Cd) on the accumulation of hydrogen peroxide (H2O2) and superoxide anion (O-2(center dot-)) in leaves of Phaseolus aureus and Vicia saliva were investigated. Cadmium at 100 mu M significantly increased the production Of O-2(center dot-) and H2O2, as well as the activities of plasma membrane-bound nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and the symplastic and apoplastic activities of superoxide dismutase and ascorbate peroxidase in the leaves of both species. Apoplastic guaiacol peroxidase activity was significantly induced in the leaves of both species, particularly in P. aureus exposed to 100 mu M Cd. Experiments with diphenylene iodonium as an inhibitor of NADPH oxidase and NaN3 as an inhibitor of peroxidase showed that the majority of C-induced reactive oxygen species production in the leaves of both species may involve plasma membrane-bound NADPH oxidase and apoplastic peroxidase. Compared to V sativa, increases in Cd-induced production of O-2(center dot-) and H2O2 and activities of NADPH oxidase and apoplastic peroxidase were more pronounced in P. aureus. In contrast, V sativa had higher leaf symplastic superoxide dismutase and ascorbate peroxidase activities than P. aureus. The results indicated that V sativa was more tolerant to Cd than P. aureus. (C) 2009 Elsevier B.V. All rights reserved.