Abstract: The effects of the plant growth regulators DA-6 and DCPTA on the metabolism of reactive oxygen species in Ziziphus jujuba Mill. cv. Dongzao during growth were investigated. DA-6, DCPTA and the control (water) were sprayed on the tree crown 3 times at blossom, 20 days and 40 days after blossom, respectively. Fruit samples were collected regularly during different growing periods. In this study, the generation rate of superoxide anion free radicals, the contents of H2O2 and MDA and the activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) were measured. The results showed that DA-6 and DCPTA treatments had no significant effect on changes in the generation rate of superoxide anion free radicals in ‘Dongzao’ jujube, but could accelerate its decline. DA-6 treatment increased H2O2 content significantly than DCPTA treatment. Both treatments dramatically increased the activities of SOD and POD in comparison with the control. DCPTA treatment increased the activity of CAT significantly at the end of the growth and inhibited the production of MDA, whereas DA-6 treatment had inhibitory effect on the activity of CAT. These finding can provide experimental data and theoretical supports for delaying the postharvest senescence of‘Dongzao’jujube.

Key words: superoxide anion free radicals, H2O2, MDA, catalase (CAT), superoxide dismutase (SOD), peroxidase (POD)