Jasmonic acid priming and foliar application of spermidine up-regulates the tolerance mechanisms to alleviate the damaging effects of cadmium stress on growth and photosynthesis in wheat

The study examined the effects of jasmonic acid (100 nmol, JA) priming and foliar application of spermidine (1 mM, Spd), both individually and combined, on mitigating cadmium (100 µM, Cd) stress-induced oxidative damage in wheat. Cadmium stress reduced plant height and dry mass, but JA priming and/or Spd treatment increased resistance. Cd stress significantly decreased carotenoids, total chlorophylls, glutamate 1-semialdehyde (GSA), and δ-aminolevulinic acid (ALA), but JA and Spd treatments counteracted these reductions. Photosynthetic parameters improved under JA and Spd treatments, with combined treatment showing greater alleviation. Cd exposure increased lipid peroxidation, hydrogen peroxide, electrolyte leakage, and superoxide, but these oxidative stress indicators were significantly reduced after JA and Spd treatment. Antioxidant enzyme activity was upregulated by JA priming and Spd application, both under unstressed and Cd-stressed conditions. JA and/or Spd treatments also increased ascorbic acid, lowered glutathione concentration, and upregulated glyoxylase activity, reducing methylglyoxal accumulation. Additionally, secondary compounds (phenols and flavonoids) and osmolytes (proline and glycine betaine) levels improved. Proline oxidase activity decreased, indicating controlled proline buildup, while γ-glutamyl kinase activity increased. JA and/or Spd treatments significantly reduced Cd accumulation in seedlings. The study concluded that JA and Spd treatments enhance the plant's defensive mechanisms against oxidative stress by boosting antioxidant enzymes and secondary metabolism.