Abstract: Rosa roxburghii Tratt‘Guinong 5’was used to investigate changes in ascorbate content and activities of some antioxidant enzymes in leaves during senescence. The results showed that O·2 generation rate, MDA content and plasma membrane permeability increased, while photosynthetic p igment and ascorbate content, POD and CAT activities decreased, significantly, together with a slow decrease in soluble protein content, with a p rogress in the leaf senescence. The change of O·2 generation rate was correlated significantly and positively withMDA content and p lasma membrane permeability, but significantly and negatively correlated with ascorbate content. The significantly negative correlation between the POD and CAT activities and the plasma membrane permeability suggests that the two enzymes played important roles in alleviating membrane damage caused by senescence.

Key words: Rosa roxburghii Tratt, Leaf, Senescence, O·2, Ascorbate, POD, CAT