Zinc nanoparticles alleviate vanadium stress in wheat (Triticum aestivum L.): impacts on vanadium accumulation, nitrogen assimilation, and amino acid profile

Zinc oxide nanoparticles (ZnO-NPs) have shown potential in mitigating vanadium (V) toxicity in plants, but their effects on V accumulation and grain nutritional quality remain unclear. To address this, we conducted a pot experiment using wheat treated with three levels of V (0, 100, and 200 mg/kg) and three levels of ZnO-NPs (0, 100, and 200 mg/kg), and systematically assessed the effects of ZnO-NPs on plant growth, V accumulation, nitrogen assimilation, and the seed amino acid profiles. Results showed that ZnO-NPs alleviated V stress by reducing V uptake and restoring growth. Compared to the control (without V and ZnO-NPs), 100 mg/kg V stress reduced total biomass and grain yield by 12.58% and 31.94%, respectively; co-application of 100 mg/kg ZnO-NPs reversed this decline, increasing total biomass and grain yield by 13.60% and 44.95% compared to V stress alone. Similarly, 100 mg/kg V stress decreased seed N, P, and K content by 8.63%, 19.12%, and 12.73%; co-application of 100 mg/kg ZnO-NPs significantly increased them by 11.64%, 22.01%, and 13.98%. Notably, the 100 mg/kg V stress also reduced the total amino acids, essential amino acids, and the essential amino acid index by 21.94%, 25.39%, and 7.12%, respectively, compared to the control; the co-application of 200 mg/kg ZnO-NPs significantly increased these indices by 21.25%, 32.06%, and 9.36%, respectively. Furthermore, under 100 mg/kg V stress, co-application of 200 mg/kg ZnO-NPs increased the valine, isoleucine, leucine, phenylalanine, histidine, and lysine contents by 12.55%, 12.45%, 13.43%, 22.01%, 59.23%, and 12.81%, respectively. These promising results provided a strong rationale for further field trials to assess the viability of ZnO-NPs as a soil amendment for safe crop production in V-contaminated environments.