Optimizing polyamine delivery: Comparative effects of foliar spray and seed priming on cotton’s chromium stress resilience

Heavy metal contamination, particularly by chromium (Cr), poses a growing challenge to sustainable cotton production. This study investigates two application strategies of the polyamine putrescine (Put, 1 mM), foliar spraying and seed priming, in hydroponically grown cotton to determine the most effective approach for mitigating Cr-induced toxicity. Under 100 µM Cr stress, application of Put improved biomass accumulation, chlorophyll content, and photosynthetic performance in cotton plants. Moreover, foliar treatment was more effective in alleviating oxidative damage, as evidenced by significant reductions in hydrogen peroxide and malondialdehyde levels. Plants treated via foliar spraying showed stronger activation of antioxidant enzymes and upregulation of stress-related genes, notably CuZnSOD , FeSOD , and APX1 . Cr uptake and mobility within plant tissues also differed between methods: foliar application notably restricted Cr translocation from roots to shoots, while seed priming promoted Cr retention in roots. Additionally, foliar spraying boosted levels of glutathione and phytochelatins and induced key sulfur metabolism genes such as CYC1 , CYC2 , and DES1 . These findings indicate that foliar delivery of Put provided measurable protective effects against Cr toxicity, suggesting its potential not only for improving cotton productivity but also for mitigating heavy metal accumulation in agroecosystems.