Effect of nickel oxide nanoparticles on the toxicity and accumulation of atrazine in soybean

: Nickel oxide nanoparticles (NiO-NPs) could impact the behavior of contaminants in the environment and affect nutrient uptake and growth of plants. In this work, we have studied the effects and mechanisms of NiO-NPs on the accumulation of atrazine by soybeans. The results revealed that NiO-NPs inhibited the uptake of ATZ in soybeans. The effects of NiO-NPs on ATZ accumulation and soybean stress responses were concentration dependent. At 5 and 50 mg/kg, NiO-NPs decreased ATZ accumulation and alleviated ATZ-induced oxidative stress in soybean, whereas at 100 mg/kg, they increased ATZ accumulation and aggravated oxidative stress. Metabolomic profiling revealed treatment-associated changes in soybean root metabolic profiles. Metagenomic analysis showed that co-exposure altered rhizosphere microbial community composition and reduced alpha diversity. Compared with ATZ alone, the 50 mg/kg NiO-NPs + ATZ treatment was associated with higher relative abundances of Nitrospirales and selected nitrogen-cycling genes; however, these shifts indicate changes in community composition and functional potential rather than direct evidence of enhanced nitrogen-cycling activity. Our findings demonstrate that NiO-NPs exerted concentration-dependent effects on ATZ accumulation and stress responses in soybean, highlighting the importance of dose when evaluating their interactions with herbicides in plant–soil systems.