Integrated Biochemical, Physiological, and Metabolite Profiling of Wheat Cultivars under Individual and combined Ozone and Water Deficit stress

NAZIYA TARANNUMNivedita Chaudhary^*

• Central University of Rajasthan, Ajmer, India

Tropospheric ozone (O₃) and water deficit stress (WS) are major abiotic factors that adversely affect wheat growth, physiology, and yield. Elevated O₃ acts as a phytotoxic pollutant, inducing oxidative stress by generating reactive oxygen species (ROS) that damage cell membranes, reduce photosynthesis, and impair overall plant development. Water deficit stress restricts water availability, leading to stomatal closure that reduces transpiration but also limits CO₂ uptake, thereby diminishing photosynthetic efficiency. Despite this, there remains a significant gap in understanding the combined effects of elevated ozone and water deficit stress on wheat. Specifically, the variability in cultivar responses and the role of stomatal and apoplastic antioxidants are not well elucidated. This study investigates the physiological and biochemical responses of four wheat cultivars RAJ-3077, RAJ-4079, RAJ-4120, and RAJ-4037 under conditions of elevated O₃ and WS, both individually and in combination. These environmental stresses modulated ROS accumulation, antioxidant enzyme activities, and stomatal behavior, ultimately influencing membrane integrity and photosynthetic pigment stability. Cultivars RAJ-4037 and RAJ-4120 demonstrated higher resilience to both individual and combined stresses, maintaining stable carotenoid and phenolic levels, exhibiting robust ROS scavenging capacity, and sustaining antioxidant defenses that preserved cellular homeostasis and delayed leaf senescence. Contrarily, RAJ-3077 and RAJ-4079 were more vulnerable to both individual and combined stresses, displaying heightened oxidative damage and compromised antioxidative capacity. While WS often induced stomatal closure that potentially limited O₃ uptake, this protective mechanism showed variability depending on cultivar traits and stress intensity. Ascorbic acid emerged as a pivotal component of O₃ defense, although the various antioxidant defenses sometimes proved insufficient under combined stresses, resulting in lipid peroxidation and cellular injury. These findings highlight important biochemical and physiological differences among cultivars, emphasizing the need to incorporate such traits into breeding and management strategies to improve wheat tolerance to multiple environmental stresses, thereby ensuring sustainable production amid the escalating climate variability and pollution.