Abstract: A series of experiments were conducted using Rhododendron hybridum and Rhododendron pulchrum to understand the effects on physiological and biochemical characteristics under different water stress. The results indicated that leaves relative water content and chlorophyll concentration of both decreased significantly and leaves appeared senescence even death with the increase of drought stress; The concentration of malondialdehyde (MDA) and leaves relative conductivity increased significantly；The concentration of solube sugar increased while soluble protein decreased, and the superoxide dismutase (SOD),peroxidase (POD)and catalase (CAT) activity increased at first then decreased; But SOD activity increased to the highest level in moderate drought while CAT and POD activity under mild water stress; Comparison of various physiological indicators showed that Rhododendron hybridum is more drought tolerant than Rhododendron pulchrum. Under waterlogging stress, two kinds of Rhododendron did not damaged seriously and the physiological indicators varied gently, and there were little significant changes compared with the control. But as the moisture stress increased, Rhododendron hybridum chlorophyll content and antioxidant enzymes activity decreased more significantly than Rhododendron pulchrum, which indicated that Rhododendron pulchrum was more water\|wet tolerant than Rhododendron hybridum. This study showed that Rhododendron plants were suitable for growing in the water sufficient soil．

Key words: Rhododendron, water stress, physiological-biochemical characteristics, antioxidant enzyme system