Iron oxide magnetic nanoparticles deteriorate the mutual interaction between arbuscular mycorrhizal fungi and plant

Purpose As a ubiquitous symbiotic fungus, the responses and the feedback of arbuscular mycorrhizal (AM) fungi to engineered nanoparticles (ENPs) remain unknown as well as the underlying mechanisms. The objective of this investigation was to figure out the influence of iron oxide magnetic nanoparticles (Fe 3 O 4 NPs) on AM fungal community, the underlying mechanisms, and the possible consequences of AM fungi-plant involved soil ecosystem. Materials and methods A greenhouse pot experiment was established to investigate the responses of maize ( Zea may L.) growth and AM fungal community to differential application levels (0.1, 1.0, and 10.0 mg kg −1 ) of iron oxide magnetic nanoparticles (Fe 3 O 4 NPs) or microscale magnetic iron oxide (bulk Fe 3 O 4 ). The AM fungal community composition and diversity were analyzed by high-throughput sequencing. The plant biomass, phosphorus (P) acquisitions, Fe concentration in plant shoots, catalase (CAT) activity, root mycorrhizal colonization rate, and glomalin-related soil protein (GRSP) contents were determined. In the meantime, the soil P supply efficiency, soil pH, and dissolved organic carbon contents (DOC) were analyzed as well as soil-soluble Fe content. Results and discussion Fe 3 O 4 NPs at 10.0 mg kg −1 (the high concentration) could be toxic to AM fungi by directly decreasing their diversity significantly ( p  < 0.05) and shifting their community structure, compared to the control and bulk Fe 3 O 4 . The similar toxicity was observed for host plant by the significant increases ( p  < 0.05) in Fe concentration in plant shoots and CAT activity. Consequently, the biomass of the host plant and the photosynthetic carbon left for AM fungi were obviously decreased ( p  < 0.05). The direct and indirect influences of Fe 3 O 4 NPs at high concentration result in the reduction of AM fungal ecological function, such as the significantly decreased ( p  < 0.05) root mycorrhizal colonization, soil GRSP content, and alkaline phosphatase activity. This process, in return, could deteriorate the nutrient provision of AM fungi for plant. As evidence, soil available P content and P nutrition in plants were significantly decreased ( p  < 0.05). Conclusions The Fe 3 O 4 NPs at high concentration would destroy the mutual interaction of AM fungi-plant and negatively influence the soil carbon accumulation and P cycling, both of which go against crop yield and soil fertility.