Effect of Exogenous Glutathione and Selenium on Cadmium-Induced Changes in Cadmium and Mineral Concentrations and Antioxidative Metabolism in Maize Seedlings

A hydroponic experiment was carried out to study the modulation of exogenous reduced glutathione and selenium in antioxidant defense system and microelement uptake against cadmium-toxicity in maize seedlings. The results showed that 50 M cadmium increased accumulation of H2O2 and malondialdehyde but reduced plant height, root length, chlorophyll content (SPAD value) and biomass. Antioxidant enzyme activities of root/leaf peroxidase and leaf superoxide dismutase increased significantly under cadmium stress, while leaf catalase decreased significantly. Moreover, cadmium-stress reduced manganese concentrations both in shoots and roots. Significantly negative correlation was discovered between manganese and cadmium concentration in different plant organs. Addition of 2.5 mu M selenium or pretreated with 100 mu M glutathione for 24 h significantly alleviated cadmium-induced growth inhibition and dramatically diminished leaf H2O2 and root malondialdehyde accumulation. Se addition or glutathione pretreatment significantly decreased cadmium concentration in roots/shoots, increased root iron level, while glutathione reduced zinc uptake. Furthermore, GSH/Se counteracted cadmium-induced alterations of certain antioxidant enzymes, e.g. brought root/leaf peroxidase and leaf superoxide dismutase activities down towards to the control level, but elevated root ascorbate peroxidase activity. These data suggest that reduced cadmium concentration and diminished cadmium-induced H2O2 and malondialdehyde accumulation in plants could be principal protective mechanism for the exogenous glutathione/selenium against cadmium toxicity.