Effects of drought priming at seedling stage on salt-tolerance physiology at flowering stage and subsequent seed setting of winter wheat

To explore cultivation techniques for improving winter wheat yield in saline-alkali soils, this study investigated the effects of seedling-stage drought priming on salt tolerance and related physiological mechanisms during later growth stages. The experiment was arranged in a completely randomised design. Three soil moisture levels – 40% (W1, severe drought), 60% (W2, mild drought), and 80% (W3, well-watered) of field capacity – were applied from emergence to jointing, followed by normal irrigation and saline irrigation at 1‰ (S1), 3‰ (S2), or 5‰ (S3) NaCl. Compared with W1 and W3, mild priming (W2) significantly reduced flag leaf malondialdehyde and sterile spikelets while increasing chlorophyll and seed-setting under saline irrigation (P < 0.05). Treatment efficacy followed W2 > W3 >W1 and diminished with increasing salinity (S1 > S2 > S3). At S1, W2S1 increased stomatal conductance, superoxide dismutase (SOD) activity, and the contents of betaine and plant brassins, grains per spike (19.5%), 1 000-grain weight, and yield per plant (34.8%) versus W3S1. At S2, W2S2 increased transpiration rate, stomatal conductance, SOD activity, and the contents of soluble sugar, plant abscisic acid, and plant gibberellins, grains per spike, 1 000-grain weight, and yield per plant (35.0%) versus W3S2. Even at S3, W2S3 maintained higher SOD activity, and higher contents of osmotic substances and plant hormones (plant brassins, plant abscisic acid, and plant gibberellins), grains per spike, 1 000-grain weight, and yield per plant than W3S3. It can be seen that this advantage in seed-setting per plant is attributed to the coordinated regulation of antioxidant enzymes, osmotic substances, hormones, and photosynthesis, effectively alleviating salt stress damage. In conclusion, mild drought priming at the seedling stage establishes a stress memory that is still detectable at 7 days after anthesis (early grain filling), enhancing salt tolerance through coordinated regulation of antioxidant enzymes, osmotic substances, hormones, and photosynthesis, ultimately improving seed-setting. These findings offer a practical approach for stabilising wheat production in saline-alkali soils.