Interactive physiological responses of Vigna radiata L. under combined heat stress and radiofrequency radiation

Abstract

Plants are increasingly exposed to multiple co-occurring environmental stressors, yet their combined effects remain insufficiently understood. In the present study, the interactive effects of heat stress (42 degrees C) and radiofrequency (RF) radiation (2.6 GHz) were investigated in Vigna radiata L. seedlings, focusing on growth, stem anatomy, stomatal characteristics, and biochemical responses under controlled conditions. Heat stress significantly reduced plant height by up to 56.3% at day 15, while RF radiation alone caused a moderate reduction (similar to 20%). Under combined stress, plant height decreased by 58.8%, closely resembling heat stress alone, indicating a predominantly heat-driven, non-additive interaction. Microscopic analysis revealed progressive structural damage, with combined stress causing noticeable epidermal disruption and poorly differentiated xylem elements compared to individual treatments. Stomatal behaviour was also largely governed by heat stress, with stomatal pore area decreasing from 28.87 mu m(2) (control) to 19.98 mu m(2) under heat and 17.54 mu m(2) under combined stress, whereas RF-treated plants showed increased pore opening (56.34 mu m(2)). In contrast, biochemical parameters showed the strongest response to combined stress. Relative water content declined from 88% (control) to 65% (heat) and 52% (combined). Similarly, carbohydrate and protein contents decreased markedly under combined stress (16.2 and 10.4 mg g(-1), respectively) compared to control (32.5 and 18.6 mg g(-1)). Chlorophyll content showed moderate reductions primarily driven by heat stress. Overall, the findings demonstrate parameter-specific responses characterized by heat-dominated structural effects and cumulative metabolic impairment under combined stress, providing new insights into RF-plant interactions under multi-stress conditions.