Evaluating the phosphorus-induced tolerance mechanism in Brassica juncea exposed to arsenic

Metalloid contamination, notably arsenic (As) toxicity, severely impacts soil, water quality, and plant development. This study evaluated the role of phosphorus (P) supplementation in mitigating As stress in 15-day-old Brassica juncea seedlings. P-deficiency was detrimental across all As concentrations, with As300-P causing the most damage. P-supplementation significantly improved morphology in As150-P seedlings compared to As50-P and As300-P, where the former exhibited rapid recovery while the latter showed limited response. Stress markers, and the activity of antioxidant enzymes increased in As150-P and As300-P treatments, with P-supplementation aiding the restoration of protein-pigment complexes. Although cysteine metabolism was initially impaired by As-P stress, it revived after P-augmentation, peaking in As300-P. Glutathione metabolism also improved with P-enrichment, particularly in As150-P. Thiol and non-protein thiol levels, elevated under stress, declined post-P supplementation, signifying stress relief. These results highlight P-enhanced S-containing detoxification pathways as key to tolerance in mustard seedlings.