Effects of Selenium(Se) on Cadmium(Cd) Accumulation, Photosynthetic Characteristics and Activities of Antioxidant Enzymes in Different Genotypes of Rape Under Cadmium(Cd) Stress

A hydroponic experiment was performed to investigate the mechanisms of Se mitigation of Cd toxicity in oilseed rapes. The effects of 0.3 mg·L-1 Se on Cd accumulation, photosynthetic characteristics and activities of antioxidant enzymes in two genotypes of rape (WH-19 and WH-95) under 0.5 mg·L-1 Cd stress were studied. The results showed that: Se application significantly decreased Cd contents in roots, stems and leaves in WH-95 with the decrease rates of 8.51%, 34.61% and 46.14% respectively compared with only Cd treatment, while no significant differences were observed in WH-19. Se greatly increased the net photosynthetic rate and the transpiration rate by 18.96% and 22.77% respectively, and significantly decreased the intercellular CO2 concentrations to 72.61% in WH-19 compared with only Cd treatment. As for WH-95, only the intercellular CO2 concentrations were significantly decreased to 85.96% under Se application, while other three photosynthetic characteristics showed no greatly changed; Se significantly decreased SOD activity in WH-19 by 29.03%, while no significant differences were observed in the activities of CAT and POD; For WH-95, 9% increase was found in CAT activity, while no marked differences were found in the activities of SOD and POD compared with only Cd treatment. Overall, Se alleviated Cd toxicities in the two oilseed rapes by enhancement of the photosynthetic system. However, the Cd accumulation and the antioxidative system showed differenct responses to Cd stress