Insight into the interaction between Fe-based nanomaterials and maize (Zea mays) plants at metabolic level

Properly understanding the fundamental interactions between engineered nanoparticles (NPs) and plants is crucial for nano-enabled agriculture. In this study, Fe and Fe₃O₄ (magnetite), which are naturally occurred nanosized crystals and minerals, were foliar applied to 4-week-old maize plants for 10 days to evaluate their impact on plant photosynthesis and growth. Hill reaction of isolated maize leaf chloroplasts was carried out to determine the performance of two Fe-based NPs on photosynthetic activities at cell level. Meanwhile, gas chromatography-mass spectrometry (GC-MS) based metabolomics was used to explore the deep insight into the interaction between Fe-based NPs and maize plants. Results showed that maize leaf net photosynthesis rate and chlorophyll content were significantly increased by Fe NPs for 19.9% and 19.3%; and Fe₃O₄ NPs for 27.5% and 26.1%, respectively. Accordingly, plant biomass has been significantly increased by Fe and Fe₃O₄ NPs by 31.8% and 34.6%, respectively. Metabolomics revealed that both Fe-based NPs induced metabolic reprogramming in maize leaves. The biosynthesis of some compatible solutes and antioxidant compounds were inhibited. In addition, exposure to Fe-based NPs tentatively shut down some energy consuming pathways, such as photorespiration, alanine metabolism, branch chain amino acid biosynthesis. The trade-off of energy consuming pathways might be alternative explanation for the enhanced photosynthesis. The results of this study exhibited the promising potential for Fe-based NPs to be used in nano-enabled agriculture to promote plant growth.