[Effects of high concentration manganese on active oxygen production and antioxidant enzyme activities in cucumber leaves under different irradiations].

Effects of high concentration manganese on active oxygen production and antioxidant enzymes in cucumber leaves under natural irradiation and 1/2 natural irradiation were studied. High concentration manganese increased the H2O2 content and O2*- producing rate of cucumber leaves (Fig.1A, B) and caused lipid peroxidation (Fig.1C). Compare to natural irradiation, 1/2 natural irradiation significantly decreased active oxygen production and lipid peroxidation (Fig.1). CAT activities in cytosols and chloroplasts were inhibited by high concentration manganese (Fig.2B), and other antioxidant enzyme activities were enhanced by high concentration manganese (Fig.2A, C-F). Especially activities of APX, DHAR and GR in chloroplasts were greatly stimulated by high concentration manganese under natural irradiation compared to 1/2 irradiation, which may play important roles in scavenging active oxygen species. Antioxidant enzymes in mitochondria showed higher activities under high concentration manganese under natural irradiation, but the differences were not significant under 1/2 natural irradiation (Fig.2A, C-F).