Physiological Effects of PEG on Chilling Resistance of Tobacco Seedlings

The tobacco seedlings was treated with different concentrations of PEG solution or water(as control) for three days, and determine the physiological index changes in leaves of tobacco seedlings such as leakage of electrolytes, the content of MDA and the contents of endogenous anyioxidants (AsA and GSH), the activities of membrane protecting enzymes(SOD and CAT)before and after chilling stress. The results indicated that treatment with PEG solution obviously increased the resistance of chilling. It also increase the content of AsA and GSH; The activities of SOD and CAT were increased by PEG and kept high level after chilling stress at 5℃ temperature. During chilling stress, in comparison with the control, the content of chlorophylls, proline and soluble sugar in tobacco seedlings treated with PEG were all increased in varying degrees. The accumulation of malondialdehyde (MAD) and the leakage of electrolytes in increased less in seedlings of PEG treated than that in control seedlings. Therefore, it was suggested that PEG had kept higher the activities of membrane protective enzymes and increased the content of protective substance for coldtolerance in tobacco seedlings under chilling stress.