Investigating Endogenous Antioxidant Responses in Plants Under Chronic Ultraviolet-B Radiation

Abstract

Chronic ultraviolet-B (UV-B) radiation poses a persistent environmental stressor that compromises plant physiological and biochemical homeostasis. This study investigated the endogenous antioxidant responses of Solanum lycopersicum (tomato) and Arabidopsis thaliana under sustained UV-B exposure (3.2 kJ m⁻² d⁻¹ for 30 days) to elucidate the dynamic defense mechanisms that mitigate oxidative stress. A time-course analysis revealed significant temporal modulation of both enzymatic and non-enzymatic antioxidants. Enzyme activities—including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX)—increased progressively, with peak activity observed at day 30, indicating an adaptive antioxidative response. Non-enzymatic antioxidants, such as glutathione (GSH) and ascorbic acid (AsA), also showed elevated levels, reinforcing their critical roles in redox buffering. Oxidative stress markers, including malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), demonstrated significant accumulation under UV-B stress, though Arabidopsis maintained lower levels than tomato, suggesting species-specific efficiency in oxidative mitigation. Gene expression profiling further confirmed the biochemical trends, showing upregulation of SOD1, CAT2, and APX1, with the highest transcript levels aligning with biochemical peaks. Correlation analysis established strong associations between antioxidant activities and the reduction of oxidative stress markers, highlighting the functional relevance of these defense pathways. Overall, the findings underscore the complex, coordinated interplay of biochemical and molecular components involved in plant acclimation to prolonged UV-B radiation. This study contributes novel insights into species-specific oxidative defense mechanisms, offering a scientific basis for breeding or engineering UV-resilient crops in light of intensifying solar radiation due to climatic changes.