Seleninm - an antioxidative protectant in soybean during senescence

Selenium (Se) is regarded as an antioxidant in animals and plants, even though considered as nonessential element in plants. To test its ability to counteract senescence related oxidative stress in soybean a pot culture experiment was conducted. The soybean plant was sprayed with sodium selenate (50 ppm) at 78 days after sowing (DAS). Soybean leaves were harvested at 80 and 90 DAS for analysis of oxidant production and antioxidative enzymes activity. Se positively promoted growth and acted as antioxidant by inhibiting lipid peroxidation and per cent injury of cell membrane. The antioxidative effect was associated with an increase in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzymes activity. Significant increase in antioxidant enzyme activity was positively related to Se content. The decrease in antioxidative enzymes at 90 DAS was much faster in control plants than Se-sprayed plants. The reduction in SOD and GSH-Px may be associated with senescence-induced oxidative burst.