Minimizing adverse effects of drought stress on maize (Zea mays L.) using foliar application of jasmonic and salicylic acids

Drought stress is a major factor limiting the growth and yield of maize (Zea mays L.). This experiment aimed to examine the effects of foliar application of salicylic acid (SA) and methyl jasmonate (MJ) in both single and combined concentrations on morphological, physiological, and biochemical traits of maize plants under varying levels of water deficit.Methods: The experiment was carried out in the greenhouse of the School of Agriculture, Shiraz University, Iran, using a completely randomized design with three irrigation levels (۱۰۰, ۷۵, and ۵۰% of full irrigation, FI) and nine foliar spray treatments (control, SA ۰.۵ and ۱ mM, MJ ۱۰ and ۲۰ μM, and four SA and MJ combinations) in ۲۰۲۲. Growth traits such as shoot height, stem diameter, leaf area, as well as fresh and dry weights of shoots and roots, SPAD index, and chlorophyll content (chlorophyll a, b, and total), along with biochemical traits including anthocyanin, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) were measured.Results: Drought stress resulted in a notable decline in vegetative growth and an elevation in oxidative indices; however, the combined treatments effectively mitigated these adverse effects. In severe drought (۵۰% FI), root dry weight increased from ۲.۰ g in the control to ۴.۶ g in the SA۱&MJ۲۰ treatment. Leaf area, which was less than ۴۰۰ cm² in the control, was found to be ۴۸۷ and ۴۵۶ cm² with SA۰.۵&MJ۱۰ and SA۰.۵&MJ۲۰, respectively. The SA۱&MJ۱۰ combination maintained total chlorophyll above ۱.۲ mg g-¹ FW under ۱۰۰% FI conditions and preserved chlorophyll a at a higher level than the control during ۷۰% FI. The combinations also resulted in the greatest reduction in H۲O۲ and MDA; under ۵۰% FI, H۲O۲ and MDA levels decreased from ۰.۴۷ and ۸۸ µmol g-¹ FW in the control to ۰.۲۸ and ۲۸.۷ µmol g-¹ FW in the SA۰.۵&MJ۱۰ treatment. Furthermore, the anthocyanin content in the combined treatments, particularly SA۱&MJ۲۰, reached levels exceeding ۶.۰ mmol g-¹ FW, indicating an enhancement of secondary defense pathways and protection against reactive oxygen species. Similarly, the individual application of SA or MJ also exerted positive effects on several growth and biochemical traits depending on the irrigation level, indicating that single-hormone treatments also could be beneficial under specific FI conditions.Conclusion: Reducing irrigation from ۱۰۰% FI to ۷۵% FI and ۵۰% FI impaired growth and pigments and enhanced oxidative damage. Effects of SA and MJ were trait- and FI-dependent. Overall, SA&MJ (especially SA۱&MJ۲۰ and SA۰.۵&MJ۱۰) tended to better support biomass under ۵۰% FI, whereas MJ alone often maintained SPAD/chlorophyll more effectively under ۷۵% FI. Thus, SA and MJ should be applied using a target-trait, FI-specific strategy, with co-application as a conditional option.

کلیدواژه ها:

Drought Stress ، Maize (Zea mays L.) ، Methyl jasmonate ، Salicylic acid