Comparative Sensitivity of Two Vigna Species to UV-B Stress: Impacts on Oxidative Stress and Antioxidant Responses

Abstract

     The study investigated the differential effects of ultraviolet-B (UV-B) radiation (0.4 W m⁻²; 280–315 nm) on hydroponically grown seedlings of two Vigna species, Vigna radiata and Vigna unguiculata, focusing on growth, reactive oxygen species (ROS), lipid peroxidation, membrane stability, and antioxidant responses. UV-B exposure inhibited growth in both species in a dose-dependent manner, with V. unguiculata showing greater sensitivity. The radiation triggered increased ROS production—specifically superoxide radicals (SOR) and hydrogen peroxide—along with elevated lipid peroxidation and electrolyte leakage, effects that were more pronounced in V. unguiculata. Antioxidant enzyme activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), were higher in V. unguiculata and initially increased under UV-B stress; however, higher doses led to a sharp decline in CAT and SOD activities. In contrast, V. radiata exhibited significantly higher levels of ascorbic acid and UV-B-absorbing flavonoids, which increased with UV-B exposure, while V. unguiculata accumulated more proline. The findings suggest that V. radiata’s greater tolerance to UV-B stress stems from its elevated ascorbic acid and flavonoid content in the epidermal layer, acting as effective UV-B screens. Conversely, V. unguiculata’s heightened sensitivity likely results from the rapid drop in CAT and SOD activities coupled with excessive ROS accumulation under UV-B stress.