Physiological and Metabolic Reprogramming of Rice ( Oryza sativa L.) under Gamma Irradiation: Insights into Antioxidant Defense and Free Radical Dynamics

) was determined to be 250 Gy, indicating strong radiosensitivity beyond this level. Growth parameters decreased dose-dependently, implying disrupted cell division and metabolism. Photosynthetic pigments such as chlorophyll a and b decreased at higher doses, while carotenoids peaked at 250 Gy, suggesting a dose-dependent stress response before declining due to ROS-induced damage. Metabolites like carbohydrates, proteins, and amino acids initially increased (peaking at 250 Gy), reflecting stress-adaptive metabolic changes. Proline levels rose consistently with dose, serving as an indicator of stress tolerance. Antioxidant enzymes (CAT, POD, and SOD) showed significant increases, helping mitigate lipid peroxidation (as evidenced by MDA content) and scavenging reactive oxygen species (ROS). Phenolic and flavonoid content also increased, contributing to ROS detoxification. Histochemical staining indicated increased ROS levels, while ESR spectroscopy revealed the formation of irradiation-induced stable radical species, likely representing secondary radicals derived from endogenous biomolecules. FTIR spectroscopy revealed dose-dependent biochemical changes in functional groups of irradiated seeds. Overall, the study highlights that gamma irradiation modulates antioxidant defense and metabolic profiles in rice, enhancing stress adaptation. These findings confirm gamma rays influence ROS management and induce functional and biochemical changes in rice plants.