Allantoin regulated oxidative defense, secondary metabolism and ions homeostasis in maize (Zea mays L.) under heat stress

Understanding how maize responds to temperature stress is crucial for improving its resilience and productivity under changing climate conditions. Previous studies have shown that exogenous allantoin (ALA) regulates various physiological processes in plants under cadmium and salinity stress. The existing body of literature provides limited insight into the specific mechanisms that govern the impact of ALA on the physiological and biochemical responses of maize plants under heat stress. This study aims to investigate the role of ALA in regulating oxidative defense, secondary metabolism, and ion homeostasis in maize under heat stress, with the ultimate goal of improving maize resilience and productivity. The current investigation displayed visible depression in growth, chlorophyll content, and nutrient uptake in maize cultivars (tolerant cv. Pearl and sensitive cv. Pak-afgoi) under heat stress. Heat stress raised MDA and H₂O₂ levels in plants, indicating hampered ROS detoxification that might have impeded nutrient acquisition in plants more profoundly in heat-sensitive cv. Pak afgoi. ALA (150 and 300 mg L⁻¹) promoted plant heat stress tolerance. ALA (300 mg L⁻¹) increased enzymatic antioxidant activities and antioxidant molecule buildup, which diminished cell ROS levels. ALA increased osmolyte accumulation, raised chlorophyll and nutrient uptake, and mitigated oxidative damage in maize under heat stress. After 72 h of recovery from heat stress, ALA significantly enhanced biomass, photosynthetic pigments, ROS detoxification, and nutrient uptake while minimizing oxidative damage, aiding rapid plant recovery from heat stress.