Seed hydropriming and amino acid sprays mitigate drought stress impacts on rainfed wheat biochemistry and yield under supplementary irrigation

Abstract The two-year study (2020–2022) investigated the effects of seed hydropriming, supplementary irrigation and foliar amino acid application on a rainfed wheat cultivar at Ekbatan Research Station, Hamedan, Iran. Conducted in a randomized complete block design with three replications and a factorial arrangement, the experiment evaluated three factors: supplementary irrigation (applied at sowing, flowering, grain filling or no irrigation), seed hydropriming (soaking seeds in tap water for 10 hours vs. unprimed) and foliar sprays (lysine, methionine at 50 mg/l, or water) at the heading stage. The absence of supplementary irrigation maximized leaf soluble protein content. Foliar application of amino acids reduced leaf proline levels by 5 %. The highest proline accumulation was observed in the second year under non-irrigated and unprimed conditions. Supplementary irrigation during flowering and methionine foliar spray decreased catalase activity by 9.7 and 2.6 %, respectively, compared to their controls. In the second year, with an 18 % reduction in rainfall, seed hydropriming increased superoxide dismutase activity by 28 %, carotenoid content by 21 % and grain yield by 28.6 % compared to unprimed seeds. Supplementary irrigation at flowering with seed hydropriming enhanced total chlorophyll by 39.1 % relative to unprimed seeds. Methionine application increased grain yield by 5.4 % compared to water spray. Therefore, seed hydropriming with tap water, supplementary irrigation at flowering and methionine foliar application are recommended to enhance rainfed wheat growth and yield in Hamedan.