Monitoring the Environmental Effects of CeO_2 and ZnO Nanoparticles Through the Life Cycle of Corn (Zea mays) Plants and in Situ μ-XRF Mapping of Nutrients in Kernels

摘要

Information about changes in physiological and agronomic parameters through the life cycle of plants exposed to engineered nanoparticles (NPs) is scarce. In this study, com (Zea mays) plants were cultivated to full maturity in soil amended with either nCeO_2 or nZnO at 0, 400, and 800 mg/kg. Gas exchange was monitored every 10 days, and at harvest, bioaccumulation of Ce and Zn in tissues was determined by ICP-OES/MS. The effects of NPs exposure on nutrient concentration and distribution in ears were also evaluated by ICP-OES and μ-XRF. Results showed mat nCeO_2 at both concentrations did not impact gas exchange in leaves at any growth stage, while nZnO at 800 mg/kg reduced net photosynthesis by 12%, stomatal conductance by 1596, and relative chlorophyll content by 1096 at day 20. Yield was reduced by 38% with nCeO_2 and by 49% with nZnO. Importantly, μ-XRF mapping showed that nCeO_2 changed the allocation of calcium in kernels, compared to controls. In nCeO_2 treated plants, Cu, K, Mn, and Zn were mainly localized at the insertion of kernels into cobs, but Ca and Fe were distributed in other parts of the kernels. Results showed that nCeO_2 and nZnO reduced com yield and altered quality of com.