Oxalic acid enhances wheat (Triticum aestivum L.) resilience to combined abiotic stresses through integrated physiological and rhizospheric microbial modulation

Soil contamination and abiotic stress have become serious global problem due to rapid development of social economy. Oxalic acid (OA), an important organic acid and fertilizer component, has been found effective in enhancing plant tolerance against various abiotic stresses. For this purpose, we have designed the current experiment to explore the contribution of OA in mediating growth and eco-physiology by alleviating abiotic stresses, in wheat ( Triticum aestivum L.). Seedlings of T. aestivum were subjected to the different abiotic stresses including drought, salinity, heat, and cold stress, and were supplemented with exogenous OA at 5 mM. Results from the present study revealed that the abiotic stresses induced a substantial decrease in shoot length, root length, number of leaves, leaf area, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid content, net photosynthesis, stomatal conductance, transpiration rate, soluble sugar, reducing sugar, non-reducing sugar contents, calcium (Ca 2+ ), magnesium (Mg 2+ ), iron (Fe 2+ ), and phosphorus (P) contents, microbial diversity, richness, and evenness in T. aestivum plants. In contrast, abiotic stresses in the soil significantly ( P < 0.05) increased phenolic content, malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ), health risk indices, bioaccumulation factors. Although, the activities of enzymatic antioxidants such as superoxide dismutase, peroxidase, catalase, ascorbate peroxidase in the T. aestivum plants and non-enzymatic such as phenolic, flavonoid, ascorbic acid, and anthocyanin contents were increased with the exposure of abiotic stresses. The application of OA significantly improved photosynthetic efficiency, microbial diversity, richness, and evenness, while reducing health risk indices, bioaccumulation factors, MDA, and H 2 O 2 contents under stress conditions. Proteomic and transcriptomic profiling further supported the regulatory role of OA in modulating stress-responsive signaling pathways and enhancing stress tolerance in T. aestivum plants. Increased antioxidant enzyme activities in OA-treated plants appeared to play a crucial role in scavenging stress-induced reactive oxygen species. Research findings, therefore, suggested that OA application can ameliorate abiotic stresses toxicity in T. aestivum seedlings and resulted in improved plant growth and composition under abiotic stresses.