Repeated drought stimuli increased wheat yield and drought tolerance by improving photosynthesis and antioxidant defense during recovery

The effects of drought on wheat have been studied extensively. However, there is limited information on changes in physiological activities during rehydration.

A pot experiment was performed to investigate the effects of intermittent and persistent mild (65–75% field capacity (FC)), moderate (55–65% FC), and severe drought (45–55% FC) stress on photosynthesis, plant–water relations, antioxidant systems, osmoregulation, and yield.

The activities of ribulose-1,5-bisphosphate carboxylase (RuBPcase) and phosphoenolpyruvate carboxylase (PEPcase) decreased by 7% and 9%, respectively, under severe stress compared with those in control. Persistent severe drought resulted in 31%, 235%, and 58% reduction in leaf water content, leaf water potential, and root hydraulic conductance (L_pr), respectively, compared with the control. After intermittent moderate drought (IS2), root length and L_pr increased by 11% and 8%, respectively, compared with the control, which contributed to the improvement of leaf water status. Intermittent and persistent drought stress led to a significant increase in antioxidant enzyme activities and osmoregulatory substance contents. After 14days of rehydration, the activities of superoxide dismutase, peroxidase, and glutathione peroxidase and contents of proline and betaine increased by 53%, 33%, 20%, 17%, and 54%, respectively, compared with the control. The IS2 treatment increased the contribution of dry matter to grain, resulting in a 10% greater yield than that of the controls.

The compensatory effect induced by rehydration increased wheat yield. This improvement was attributed to improved physiological activities and drought tolerance. These findings contribute to a better understanding of responses of wheat to repeated drought stimuli.