Abstract: To analyze the effect of system-2 ethylene on the activities of catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) during exposure to cold stress, anti-sense ACS2, wild-type Lichun and ethephon-treated anti-sense ACS2 tomato fruits were used to the models of  non-system-2 ethylene synthesis, normal system-2 ethylene synthesis and compensative system-2 ethylene synthesis, respectively. It was indicated that wild-type Lichun and ethephon-treated anti-sense ACS2 tomato fruits decreased chilling injury index, inhibited the increase of electrolyte leakage and increased the average activities of CAT, APX and SOD compared with native anti-sense ACS2 tomato fruits. The increase of POD activity was inhibited in wild-type Lichun but induced in ethephon-treated anti-sense ACS2. From these results, it can be concluded that system-2 ethylene can improve the cold resistance of tomato during exposure to cold stress by increasing CAT, APX and SOD activities and regulating POD activity.

Key words: ethylene, antioxidant enzymes, oxidative stress, cold resistance, tomato