Deciphering growth performance and metabolic adaptation in salt-stressed Vigna unguiculata L. plants through mycorrhiza and titanium dioxide nanoparticles

Abstract Background Soil salinity is a major environmental constraint limiting crop productivity worldwide. Arbuscular mycorrhizal fungi (AMF) and titanium dioxide nanoparticles (TiO 2 NPs) have emerged as promising tools for enhancing plant tolerance to abiotic stress. However, their combined effects on salt-stressed cowpea have not been previously investigated. Therefore, a pot experiment was conducted using a completely randomized design with five replicates to evaluate the individual and combined effects of AMF consortium ( Gigaspora nigra , Glomus monosporum , G. clarum , and Acaulospora laevis ) and TiO 2 NPs (100 ppm) on cowpea plants grown under 0, 100, and 200 mM NaCl. Results Salinity significantly reduced plant growth and chlorophyll content while increasing lipid peroxidation. At 200 mM NaCl, shoot biomass and chlorophyll content index decreased by 61.13 and 39.57%, respectively, whereas lipid peroxidation increased by 153.03% compared with the control, after 45 days from sowing. However, AMF consortium or TiO 2 NPs application alleviated these adverse effects by enhancing biomass production, photosynthetic performance, and the accumulation of proteins and carbohydrates. Further, their combined (AMF + TiO 2 NPs) treatment was the most effective that markedly enhanced antioxidant enzyme activities, acid and alkaline phosphatases and improved root colonization parameters, indicating enhanced physiological and biochemical adaptation to salinity stress. Conclusion The combined application of AMF consortium and TiO 2 NPs effectively mitigated salinity-induced damage in cowpea and produced greater benefits than either treatment alone. Thus the interaction between biological and nanotechnological approaches enhanced growth, antioxidant defense, and metabolic adaptation, highlighting a sustainable strategy for improving crop productivity under saline conditions.