Abstract: Rosa roxburghii Tratt ‘Guinong 5’ was used to investigate the response of antioxidant system to mechanical wounding and UV-B stress during fruit development. The results showed that the reactive oxygen species and membrane lipid peroxidation were all induced by the both stress treatments，
but different defense response patterns of antioxidant system were observed. In wounded fruits，the antioxidant enzymes such as POD，SOD and some antioxidant substances of AsA or GSH were provoked immediately leaded by H₂O₂ production. Then，with the redox prolonged，the enzyme activities decreased gradually while the contents of AsA and GSH still maintained a high level. Longer-term supplement of UV-B radiation would contribute to SOD activity or AsA and GSH accumulation，and then to the nutritional values in the fruit. In the condition of weakened UV-B treatment （–UV），activities of SOD and POD and content of GSH increased in early development stage but decreased in ripening fruit. POD，but not CAT or APX plays a role of sensitive factor to these kinds of stress. These data reveal that cooperation of antioxidases of POD and SOD with antioxidants of AsA and GSH should be the main ROS-scavenging mechanisms to sense the environment stress and react appropriately by keeping the cellular redox balance in the fruits.

Key words: Rosa roxburghii, mechanical wounding, UV-B radiation, antioxidant system