Abstract: In the research, various chemical regulators and appropriate application dates would be tested, based on the physiological responses of winter wheat to dry hot wind stress that contains different efficient components. A field experiment was conducted in Huang-Huai-Hai plain from 2020 to 2021, where dry hot wind disasters were frequently. Six treatments (foliar spraying with tap water (CK) and KH₂PO₄ (CKP) both at jointing and flowing stage as controls; foliar spraying with phosphorus-A preparation at jointing stage (BA) and flowering stage (HA); foliar spraying with phosphorus-E preparation at jointing stage (BZ) and flowering stage (HZ)) were conducted, and leaf area index (LAI), leaf fluorescence parameters, key enzyme activities of starch synthesis, and starch accumulations, dynamics of grain filling in superior and inferior grains, yield and its components of damaged wheat were compared. The winter wheat experienced two mild dry-hot wind stresses on 24 and 26 days after flowering (DAF). Compared with CK treatment, BA (6341.35kg∙ha−1) and HZ (6454.23kg∙ha−1) treatments significantly increased grain yield by 9.82% and 11.78%. Moreover, these two treatments also performed better than CKP treatment, significantly increased by 8.11% and 10.03%, respectively. BA treatment had the highest grain number per panicle, and could significantly increase LAI over CKP by 47.67% on 30 DAF. While HZ treatment performed better on thousand grains weight, and the maximum photochemical efficiency (Fv/Fm), and photochemical quenching coefficiency (qP). Additionally, HA treatment made the non-photochemical quenching (NPQ) at relative low level during the period of grain filling stage. After undergoing two dry hot wind processes, compared with CKP treatment at 26 DAF, the activities of ADP-glc pyrophosphorylase (AGPase) increased by 19.26% under BZ treatment, and the activities of granule-bound starch synthase (GBSS) and soluble starch synthase (SSS) rose 2.11% and 15.92% under HZ treatment. At 30 DAF, HZ treatment elevated amylose and total starch contents by 9.75% and 3.74% than CKP treatment, respectively. The curve fitting with Richards equation showed that foliar-applications of various chemical regulators had a positive impact on wheat resistance and alleviated dry hot wind damage, through delaying the occurrence of the maximum grain-filling rate (T_max∙G) and rising grain-filling rates. Moreover, HA treatment could increase the maximum grain-filling rate (G_max) of inferior and superior grains by 22.71% and 18.30%, and the mean grain-filling rate (G_mean) of the two grain positions performed the increase of 19.27% and 12.72% compared to CKP treatment. Above all, varieties of regulators and application dates ultimately led to varied physiological regulation pathways on leaves and grains of wheat. When separately spraying at the jointing and flowering dates, the optimal regulation benefits of phosphorus-A and phosphorus-E could be stimulated to alleviate the damage of dry hot wind on winter wheat, and HZ treatment was recommended as the most effective method to prevent wheat from the detriment of dry hot wind stress.

Key words: Dry-hot wind, Winter wheat, Chemical regulator, Leaf fluorescence, Grain-filling dynamic, Yield