Biochar modulates morphophysiological traits and yield stability in Phaseolus vulgaris L. via biochemical adjustments under tropospheric Ozone stress

Introduction Tropospheric ozone (O 3 ) is a major abiotic environmental stressor in the Indo-Gangetic plains of India due to more conducive conditions for O 3 formation, such as emissions of large amounts of O 3 precursors (VOCs, NOx), prolonged sunshine hours, and high temperatures, causing significant losses in crop productivity. Among various mitigation approaches, biochar has emerged as a viable and economical soil amendment with multifaceted benefits in improving plant resilience against abiotic stressors. Methods This field study investigates the efficacy of biochar amendment in mitigating O 3 -induced phytotoxicity in two popularly grown cultivars (HUR-137 and PDR-14) of Kidney beans ( Phaseolus vulgaris L.). Biochar was applied at 2.5% and 5% (w/w) under ambient and elevated O 3 exposures. Key markers of plant growth, development, biochemical and yield were assessed, supported by histochemical and chlorophyll fluorescence parameters to determine physiological and antioxidative responses. Results and discussion Biochar fertilizations (2.5 and 5% w/w) significantly ameliorated O 3 -induced growth and total biomass reductions. Improvements in floral metrics were noted in biochar-treated test plants. Histochemical analyses revealed reduced oxidative damage, followed by enhanced stimulation of antioxidative defense observed in biochar amendments as reflected by biochemical assays. Plant pigments and chlorophyll fluorescence parameters reflected improvements in biochar treatments. Biochar supplementation protected yield traits under O 3 stress, improving pod formation, seed filling, and productivity in both the test cultivars. Under O 3 stress, unamended plants of PDR-14 (EOB0) displayed more pronounced results with 44.7% reduction in GWP (17.46 g plant−1, 95% Confidence Interval, 15.32–19.60), relative to ambient O 3 conditions (31.58 g plant−1, 95% CI, 27.78–35.38). The application of 5% biochar (EOB5) ameliorated O 3 -induced yield reduction (23.06 g plant−1, 95% CI, 20.60–25.53), depicting 32.1% improvements compared to EOB0. Overall findings suggest that biochar application is a potential agronomic strategy to maintain productivity in Phaseolus vulgaris (L.) cultivars in areas experiencing high concentrations of O 3 .