Intermittent Drought Priming Improves Photosynthesis, Water Status, Antioxidant Capacity, and Tolerance to Drought Stress in Winter Wheat

Improving the drought tolerance of wheat in response to post-flowering stress through appropriate water deficit priming is essential to enhance its production potential. However, the effects of the number of priming events and degree of pre-exposed stress on the physiological traits, growth, and yield of wheat remain unclear. The purpose of this study was to investigate the effects of intermittent and persistent drought priming on photosynthesis, water status, antioxidant capacity, phytohormone content, and yield and to comprehensively evaluate the drought tolerance of wheat. Plants subjected to intermittent moderate drought priming (PID2) and persistent mild drought priming (PPD1) exhibited improved photosynthetic parameters, pigment accumulation, plant-water relations, root activity, and phytohormone synthesis. Under subsequent drought stress, the relative leaf water content of PID2 and PPD1 plants increased by 14% and 10%, respectively, compared with no stress priming (NPD). This phenomenon may be attributed to the higher root hydraulic conductivity and root viability observed in the PID2 plants. When compared with the NPD plants, the levels of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in the PID2 plants increased by 108%, 54%, and 198%, respectively. In addition, the proline content was 116% and 97% higher in PID2 and PPD1 plants, respectively. The reduction in reactive oxygen species and malondialdehyde content further confirmed the alleviation of oxidative stress. Furthermore, the drought tolerance index of PID2 plants was significantly greater than that of NPD plants, resulting in harvest indices and grain yields that were 16.16% and 26.92% higher, respectively, than those of the NPD plants. These findings suggest that implementing intermittent moderate drought priming during the jointing period may serve as a promising strategy for enhancing drought tolerance and increasing wheat yield in arid and semi-arid regions.