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.