Abstract: The purpose of this paper is to explore the effects of exogenous application nitrogen in nutrient solution on the activity of antioxidant enzymes and function of mitochondria in cherry rootstock roots under hypoxia stress. The cherry rootstock seedlings were cultured in 1 /2 Hogland nutrient solutions of different NO₃^- concentration (0, 7.5, 15.0, 22.5 mmol·L ^{- 1} ). The oxygen concentration of the nutrient solution dissolved was controlled 2 mg·L ^{- 1}. Under the normal oxygen condition, 7.5 mmol·L ^-1 NO₃^- was a control.
The results showed that the activities of SOD, POD and CAT of cherry rootstock roots in the four treatments were all increased at the first four days and then decreased. Compared with the control, the activities of SOD, POD and CAT of cherry rootstock roots after the treatmentwith 15 or 22.5 mmol·L ^{- 1} NO₃^- increased and the MDA content decreased. The contents of H₂O₂ andMDA, production rate of O₂^-·in mitochondria of the treatment with nitrogen deficiency were the most among the four treatments. Additional nitrogen into the nutrien solution under hypoxia stress could decrease contents of H₂O₂ and MDA, production rate of O₂^-·, and increase the cytochrome c / a and the rate of respiration ofmitochondria by increasing resp iratory control ratio and oxidative phosphorilation ratio. The above results suggested that exogenous nitrogen application in nutrient solution could antagonize the damage of hypoxia stress on cherry seedlings.

Key words: cherry, hypoxia stress, nitrogen, antioxidant enzymes, mitochondria