Assessing the combined impacts of microplastics and nickel oxide nanomaterials on soybean growth and nitrogen fixation potential.

The excessive presence of polystyrene microplastic (PS-MPx) and nickel oxide nanomaterials (NiO-NPs) in agriculture ecosystem have gained serious attention about their effect on the legume root-nodule symbiosis and biological nitrogen fixation (BNF). However, the impact of these contaminants on the root-nodule symbiosis and biological N ₂ -fixation have been largely overlooked. The current findings highlighted that NiO-NMs at 50 mg kg ^-1 improved nodule formation and N ₂ -fixation potential, leading to enhanced N ₂ uptake by both roots and shoots, resulting in increased plant growth and development. While single exposure of PS-MPx (500 mg kg ^-1 ) significantly reduced the photosynthetic pigment (8-14 %), phytohormones (9-25 %), nodules biomass (24 %), N ₂ -related enzymes (12-17 %) that ultimately affected the N ₂ -fixation potential. Besides, co-exposure of MPx and NiO at 100 mg kg ^-1 altered the nodule morphology. Additionally, single and co-exposure of MPx and NiO-NMs at 100 mg kg ^-1 reduced the relative abundance of Proteobacteria, Gemmatimonadota, Actinobacteria, Firmicutes, and Bacteroidetes is associated with N ₂ -cycling and N ₂ -fixation potential. The findings of this study will contribute to understanding the potential risks posed by MPx and NiO-NMs to leguminous crops in the soil environment and provide scientific insights into the soybean N ₂ -fixation potential.
Competing Interests: Declaration of Competing Interest The authors declare that they have no financial or personal relationships that could influence the research work presented in this manuscript. There are no conflicts of interest regarding the publication of this research.
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