Abstract:
Physiological responses to chilling were investigated in sorghum plants to identify the mechanisms of chilling
tolerance. The experiment was conducted in the botany laboratory of Faculty of Education Ain Shams University. 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 4ºC or 8ºC for 7d. and allowed to recover at 25ºC for 3 days. Selenate at lower concentrations (3 and 6 mg L–1) enhanced the growth and levels of chlorophylls (Chl), anthocyanine, sugar, proline(Pro), ascorbic acid(Asc) and enzymatic activities. However, high levels of selenate (12 mg L–11) exerted toxic effects. The levels of non-enzymatic antioxidants (ascorbic acid) were increased by selenate while the levels of carotenoids (Car) were decreased. Low selenate (3 and 6 mg L-1) reduced lipid peroxidation as measured by malondialdehyde (MDA). The activities of enzymatic antioxidants showed different responses to selenate, guaiacol peroxidase, (GPX), in seedlings they were enhanced by low level of selenate (3 and 6 mg L–1) while ascorbic acid peroxidase (APX) increased only at (12 mg L–1) of sodium selenate. The results showed that both low selenate (3 and 6 mg L–1) especially 3 mg L–1 induced cold tolerance in the seedlings. This study explained the effects of low selenate level for young seedlings under cold stress.
