| Drought stress is a limiting factor for plant cultivation in many areas of China. In present study, the blackberry cultivar 'Hull Thornless' was chosen for drought stress analysis. All plants were grown in pots under greenhouse conditions, and were subjected to 20-day drought stress by withholding irrigation, followed by re-watering for 5 days. The changes in leaf water content (LWC), electrolyte leakage (EL), concentrations of photosynthetic pigments, protein, soluble sugar, hydrogen

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... (H 2 O 2 ), malondialdehyde (MDA), ascorbate (AsA) and reduced glutathione (GSH), activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves of 'Hull Thornless' were investigated. In the treatment group, water stress significantly increased EL, and the accumulation of photosynthetic pigments, protein, soluble sugar, H 2 O 2 and MDA. After re-watering, all of those parameters showed decreases of different degree. LWC was significantly decreased in response to drought treatment. However, after 5 days of re-watering, the LWC restored. Moreover, SOD activity increased gradually under drought stress, except for the day 15. After re-watering, SOD activity was still at higher level. Under drought treatment, POD activity and levels of AsA and GSH first ascended and then followed by a decline. After re-watering, they all decreased, but AsA and GSH levels were remain higher than the controls. The results indicated that the tolerance of blackberry cultivar 'Hull Thornless' to drought stress was enhanced by activating the antioxidant system, and altering the levels of photosynthetic pigments.