The physiological response of winter wheat under short-term drought conditions and the sensitivity of different indices to soil water changes

Studying the physiological responses of winter wheat to drought is conducive to learning to utilize biological water-saving technologies, such as regulating deficit irrigation and obtaining higher water use efficiency (WUE). However, the close relationship between the trend of responses of physiological functions in wheat and changes in soil moisture merits further study. In this study, a two-season pot experiment with three levels of water deficit (45 %-75 % FC, field capacity) was established at three growth stages, based on the theory that the drought resistant physiological functions of winter wheat could respond to regulated deficit irrigation. The goal was to explore the effects of short-term drought-re-watering on yield and WUE and the sensitivity of wheat leaf physiological indicators to reflect changes in soil moisture. The results showed that the short-term drought in different periods after the jointing period reduced the yield of winter wheat by 2.03 %-64.39 % compared with the treatment of an adequate supply of water (75 %-85 % FC). Priority should be placed on ensuring irrigation during the jointing and filling periods. Treatments that experienced drought during the heading period (55 %-75 % FC) and then recovered to 75 %-85 % FC after flowering can improve the WUE by 5 %-22 %. The physiological function of drought resistance in winter wheat leaves responds noticeably to drought and the re-watering process in the range of 45 %-85 % FC. The maximum values of the activities of superoxide dismutase (SOD) and peroxidase and the contents of malondialdehyde and proline (Pro) during drought increased by 51.9 %, 15.1 %, 40.4 %, and 157.2 %, respectively, compared with those of the control group. The activity of catalase primarily increased after rehydration, and the maximum value was 1.5-fold that of the control group. After 14 days of rehydration, the physiological index values of multiple treatments can be restored to the level of control, which proves that the physiological response within the range of 45 %-85 % FC water change is reversible. Based on the experimental data of the two seasons, the changes in activity of SOD and content of Pro more effectively reflect the changes in soil moisture than the other indicators (ROC analysis, AUC = 0.720-0.978) and have a significant correlation with yield (P < 0.05). Therefore, they can be considered as physiological reference tools to monitor the effect of irrigation and adjust its strategy.