The role of hydrogen peroxide in cadmium-inhibited root growth of rice seedlings (original) (raw)

Cadmium (Cd) is readily taken up by the roots of rice seedlings, leading to growth reduction. H 2 O 2 is a constituent of oxidative metabolism and is itself a reactive oxygen species. In this study, the participation of H 2 O 2 in CdCl 2-inhibited growth of rice roots was investigated. CdCl 2 treatment increased H 2 O 2 production in rice roots. CdCl 2 treatment had no effect on the activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase, but inhibited the activity of catalase (CAT) in rice roots. CdCl 2-inhibited root growth and-increased H 2 O 2 content were lessened in the presence of diphenyleneiodonium chloride, an inhibitor of H 2 O 2 generating NADPH oxidase. However, this stimulation of root growth in CdCl 2-treated seedlings is small (about 5%). Calcium (Ca) is important in many physiological processes in plants. Attempts were also made to determine whether the action of Ca on CdCl 2-inhibited growth of rice roots is associated with H 2 O 2. CaCl 2 application reduced the production of H 2 O 2 , the decrease in CAT activity, and the inhibition of root growth caused by CdCl 2. The effects of CaCl 2 application could be reversed by exogenous H 2 O 2. Our results indicate that the Cd causes a decline in CAT and to a lower extent a stimulation of NADPH oxidase in rice roots, with the subsequent generation of H 2 O 2 , an agent responsible for growth inhibition.