Abstract: Taking Dahlia pinnata ‘Fenxishi’ as test material, this paper studied its leaf physiological and biochemical responses to different degrees of drought stress and re-watering. With the increasing extent and duration of drought stress, the leaf relative water content, water potential, and chlorophyll content of D. pinnata ‘Fenxishi’ decreased significantly, leaf relative electric conductivity and malondialdehyde (MDA) content had a significant increase, plasma membrane was damaged, and massive ions were leaked out. The damage of plasma membrane was most serious under severe stress, and could not recover to the control level after re-watering. The leaf soluble sugar and proline contents also increased significantly with increasing extent and duration of drought stress. Especially for proline content, it was increased significantly in the later period of moderate and severe stresses, suggesting its lower sensitivity to water deficit. The leaf soluble protein content had a trend of down-up-down, while the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) decreased after an initial increase. There were some differences in the responses of the three enzymes to drought stress and reactive oxygen, exhibiting their coordinating role.

Key words: Dahlia pinnata, drought stress, drought resistance, physiological change