| The physiological response of Scutellaria baicalensis Georgi under different water stress and rehydration treatments was investigated by using authentic SBG and setting the potting soil water content at 100%, 80%, 60%, and 40% of the field water holding capacity to represent four treatments: excessive water supply, moderate water supply, mild water deficit, and severe water deficit, respectively, with moderate water supply as the control treatment. The results showed that During water stress (stress initiation to 30 days of stress), the water stress-treated (100%FC, 60%FC, and 40%FC treatments) resulted in lower photosynthetic pigment content, higher electrolyte leakage rate and proline content, and the activities of superoxide dismutase and glutathione reductase was rising in SBG, as compared with the control treatment (80%FC). In addition, during water stress, water deficit treatments (60%FC and 40%FC treatments) led to an increase in malondialdehyde and soluble sugar contents of SBG, and the excess water supply treatment (100%FC treatment) led to an elevation in peroxidase activity of SBG. Rehydration was effective in reducing physiological damage caused by water stress. During rehydration and harvesting, the excess photosynthetic pigments of SBG from the stress treatments (100%FC, 60%FC, and 40%FC treatments) were restored, the relative exocytosis rate of electrolytes was reduced, and the proline content and catalase activity were gradually placed at the same level as that of the control treatment (P>0.05). However, the physiological damage caused by heavy water deficit was irreversible, and the soluble sugar and malondialdehyde contents and superoxide dismutase and peroxidase activities in the 40%FC treatment were still at high levels after rehydration. Water stress and rehydration favored the yield quality of SBG roots, and at harvest, the 60%FC treatment had the highest harvest of baicalin at 629.14 mg per plant. |