Growth and Physiological Responses of Sunflower Plants To Different Methyl Jasmonate Spray Concentrations, Irrigation Periods and Plant Stages

This field experiment investigated the Flami sunflower crop’s physiological response to spraying of 0, 50, and 100 µmol methyl jasmonate (MeJA) concentrations at the 6-10 leaves and pre-flowering stages and the impact of 5, 9, and 13-day irrigation intervals. The experiment was conducted in a randomized complete block design (RCBD) with a split–split plot arrangement with three replicates. The 5-day irrigation interval achieved the best values ​​for the studied growth and physiological indicators, followed by 6 and 13 days, respectively. The MeJA spray treatment enhanced plant growth, with the highest concentration achieving the best values, producing increases in LA by 8.01%, DW by 21.69%, CGR by 14.92%, RGR by 10.65%, NAR by 18.34%, Ch. a by 22.02%, Ch. b by 24.17%, RWC by 8.65%, and proline by 17.34%, while decreasing solute leakage by 47.93% compared to control. Overall, the best interaction for growth and physiological performance of the crop was obtained for the 5-day irrigation interval and 100 µmol MeJA spray combination at the pre-flowering stage