Mitigating Cadmium Stress in Soybean Plants: Seed Priming with Nanoscale TiO2 and ZnO for Safer Crop Production

This study investigates the effects of soybean seed priming with titanium dioxide nanoparticles (TiO₂ NPs) or zinc oxide nanoparticles (ZnO NPs) on germination and plant growth under cadmium (Cd) stress. Soybean seeds were primed with TiO₂ NPs (50, 100, 200, or 400 mg/L) or ZnO NPs (50, 100, 300, or 500 mg/L) followed by Cd exposure during the germination (7 days) and plant (35 days) stages. The results demonstrate that priming with 100 mg/L ZnO NPs significantly enhanced soybean germination energy by 22.5%; 100 mg/L TiO₂ NPs and 300 mg/L ZnO NPs increased the fresh shoot and root weights by 63 and 21%, respectively, and enhanced the in-planta antioxidant capacity compared to the water-primed controls. In addition, 100 mg/L TiO₂ NPs reduced Cd accumulation by 60% in stems and by 34% in leaves. Meanwhile, 100 mg/L TiO₂ NPs and 100 mg/L ZnO NPs fixed significantly more Cd in the cell walls, thereby mitigating phytotoxicity to leaf organelles. This work demonstrates that seed priming with TiO₂ and ZnO NPs can simultaneously promote growth and alleviate the adverse effects of Cd stress on soybean and highlights the potential of this approach as a sustainable food safety strategy for crop production.