Melatonin Improves Drought Resistance in Maize Seedlings by Enhancing the Antioxidant System and Regulating Abscisic Acid Metabolism to Maintain Stomatal Opening Under PEG-Induced Drought

Abstract Maize ( Zea mays L.) is highly sensitive to drought stress, resulting in large losses yield; therefore, strategies aimed at enhancing tolerance are essential. Melatonin improves stress plants; however, its mechanism maize seedlings under remains unknown. Therefore, we investigated the effects of foliar-sprayed melatonin (100 umol L −1 ) on antioxidant system, photosynthetic gas exchange parameters, stomatal behavior, endogenous and abscisic acid (ABA)-related gene expression seedling leaves 20% polyethylene glycol (PEG)-induced stress. PEG treatment resulted oxidative closure, chlorophyll degradation inhibition photosynthesis; thereby, reducing biomass. pretreatment significantly improved relative water content, parameters behavior; maintaining contents photosynthesis. also stimulated clearance reactive-oxygen species, preventing severe damage PEG-induced drought. Pre-treatment increased inhibited up-regulation NCED1 , an ABA synthesis-related gene, as well selectively up-regulating catabolic genes ABA8ox1 ABA8ox3 accumulation inducing reopening. Overall, these findings suggest that pre-treatment alleviated inhibitory photosynthesis, seedlings.