Effects of low temperature and selenium application on growth and the physiological changes in sorghum seedlings

Cold temperature damage is a common problem for plant in temperate regions. Physiological responses to low temperature were investigated in sorghum to identify mechanisms of tolerance. Sorghum (Sorghum bicolor L.) seeds were soaked in different concentrations (0, 3, 6 and 12 mg L-1) of sodium selenate for 6 h before sowing, during the germination period seedlings were exposed to 4 °C or 8 °C for 7 days and allowed to recover at 25 °C for 3 days. Selenate at lower concentrations (3 & 6 mg L-1) enhanced the growth and levels of chlorophylls, anthocyanine, sugar, proline, ascorbic acid and enzymatic activities. However, high level of selenate (12 mg L-1) exert toxic effects. The levels of non-enzymatic antioxidants (ascorbic acid and carotenoids) were increased by selenate. Low selenate (3 & 6 mg L-1) diminished lipid peroxidation as measured by malondialdehyde. The activities of enzymatic antioxidants (ascorbic acid peroxidase and guaiacol peroxidase) in sorghum seedlings were enhanced by low level of selenate. The results showed that both enzymatic and non enzymatic antioxidants played significant roles in selenate detoxification.