Biochar modulates morphophysiological traits and yield stability in Phaseolus vulgaris (L.) via biochemical adjustments under tropospheric O3 stress

Vineet Upadhyay¹Krishna Kumar Choudhary^1*Madhoolika Agrawal²Shashi Bhushan Agrawal^2*

• ¹Department of Botany, Mahila Maha Vidyalaya, Banaras Hindu University, Varanasi, India
• ²Banaras Hindu University Department of Botany, Varanasi, India

Tropospheric ozone (O3) is a major abiotic environmental stressor in the Indo-Gangetic plains of India due to more conducive conditions for O3 formation, such as emissions of large amounts of O3 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. This field study investigates the efficacy of biochar amendment in mitigating O3-induced phytotoxicity in two popularly grown cultivars (HUR-137 and PDR-14) of Kidney beans (Phaseolus vulgaris L.) by analyzing key markers of plant growth, development, and yield. Biochar fertilizations (2.5% and 5% w/w) significantly ameliorated O3-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 O3 stress, improving pod formation, seed filling, and productivity in both the test cultivars. Under O3 stress, unamended plants of PDR-14 (EOB0) displayed more pronounced results with 44.7% reduction in GWP (17.46 g plant-1, 95% CI: 15.32–19.60), relative to ambient O3 conditions (31.58 g plant-1, 95% CI: 27.78–35.38). The application of 5% biochar (EOB5) ameliorated O3-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 O3.