Effects of 1-MCP on the Mitochondrial Antioxidant Activity and Energy Metabolism of Zucchini Fruits

In order to explore the effects of 1-methylcyclopropene (1-MCP) treatment on mitochondrial reactive oxygen metabolism and energy metabolism of zucchini fruits stored at room temperature, this study took 'Taishan Green' zucchini as test materials. The fruits were fumigated with 20 μL·L⁻¹ 1-MCP at room temperature for 24 h and then stored at room temperature (20±1) ℃ for 12 d. The physiological quality, mitochondrial antioxidant properties and energy metabolism change of zucchini fruits were determined every 3 d during storage. Results showed that: On the 12th day at the end of storage, the weight loss of 1-MCP treated zucchini fruit was only 54.6% of that of the control, and the total phenol content was 1.44 times of the control. During storage, the respiration intensity of fruits was significantly lower than that of control fruits (>10 mg·kg⁻¹·h⁻¹) (P<0.05), 1-MCP treatment also decreased the content of malondialdehyde and hydrogen peroxide in mitochondria of zucchini and inhibited the production rate of superoxide anion. The hydrogen peroxide content and superoxide anion production rate of the treated fruits were 17.45% and 23.29% lower and 10.51% and 7.62% lower than those of the control group, respectively. 1-MCP treatment kept the activities of superoxide dismutase and ascorbate peroxidase higher in mitochondria of zucchini fruits, decreased the activities of lipoxygenase. The mitochondrial superoxide dismutase activity in the treatment group was 1.23 and 1.15 times of that in the control group at the 3rd and 6th day of storage. In addition, 1-MCP treatment also delayed the decrease of the activities of succinate dehydrogenase, cytochrome C oxidase, mitochondrial H⁺-ATPase and mitochondrial Ca²⁺-ATPase. On the sixth day of storage, the activities of four enzymes of zucchini fruits treated with 1-MCP were significantly higher than those of the control (P<0.05), the activities of H⁺-ATPase and Ca²⁺-ATPase were 1.05 and 1.22 times than those of the control. Therefore, 1-MCP could reduce the oxidative damage of mitochondrial membrane of zucchini fruits, maintain the integrity of mitochondria, delay the process of maturation and senescence, and prolong the storage period of zucchini fruits.