Quantitative and qualitative comparison of antioxidant activity in the flavedo tissue of three cultivars of citrus fruit under cold stress

摘要

Low temperatures constitute a major risk for the production of citrus fruit because citrus plants are sensitive to low temperatures and harvesting coincides with winter. The production of reactive oxygen species (ROS) is a biochemical change in plants facing cold stress. Plants may increase levels of antioxidants as an adaptation for preventing oxidative stress. In this study, three citrus cultivars (Citrus unshiu, Citrus sinensis and Citrus lemon) were examined to compare the activities of three antioxidants: ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD), in the flavedo tissue of unripe and ripened fruits. Enzyme activity levels were examined under various cold temperature treatments (range: 3, 0, -3 and -6°C) and a control (15°C). The results indicate that SOD activity was highest in all three cultivars under cold treatments. Unripe and ripened Citrus unshiu fruits had the maximum level of APX enzyme activity in the cold treatments. Similarly, the activity of POD enzyme in Citrus unshiu fruits significantly increased during temperature reductions. Overall, Citrus unshiu appears the most resistant to cold treatments compared with the other two cultivars.