Physiological and metabolic responses of maize (Zea mays) plants to Fe3O4 nanoparticles.

Fe3O4 nanoparticles (NPs), as representative magnetic materials, have been widely used in the industrial and biomedical sectors, and their environmental impacts must be evaluated for their sustainable use. In this study, the interactions between Fe3O4 NPs and maize plants were investigated by a combination of phenotypic and metabolic approaches. Maize plants (Zea mays) were grown in soil treated with Fe3O4 NPs at 0, 50 and 500 mg/kg for 4 weeks. Fe3O4 NPs had no impact on plant biomass or photosynthesis. However, root length of maize plant significantly increased, with decreased malondialdehyde (MDA) level, indicating the positive effects on root development and membrane integrity. Inductively coupled plasma optical emission spectrometry (ICP-OES) revealed that Fe3O4 NPs resulted in a significant Fe accumulation in roots, instead of leaves. In addition, 500 mg/kg Fe3O4 NPs significantly promoted dehydrogenase enzyme activity by 84.9%. Metabolomics revealed that maize root metabolomes were re-programmed by Fe3O4 NPs exposure. Metabolic pathways associated with antioxidant and defence were inactivated by Fe3O4 NPs, indicating the protective role of Fe3O4 NPs for microbes and plant roots. Taken together, the results indicate a limited impact of environmental Fe3O4 NPs on plant growth. Taken together, the results of this study offer new insights into the molecular mechanisms by which maize responds to Fe3O4 NP exposure.