Uptake, Transport, and Transformation of CeO2 Nanoparticles by Strawberry and Their Impact on the Rhizosphere Bacterial Community

Many studies demonstrated that CeO2 nanoparticles (NPs) could protect plant from stress and improve plant growth, with a great application potential in agriculture. However, our knowledge of their fate particularly in asexual plants and their effect on the rhizosphere microbiome is limited. In this study, the transport and transformation of CeO2 NPs in an asexual plant—strawberry (Fragaria × ananassa Duch.)—were investigated. The effects of root-exuded/newly formed Ce species on rhizosphere bacterial community were also examined. Strawberries were exposed to CeO2 NPs at 0–2000 mg/L for 45 days via a split-root system in the field. CeO2 NPs were taken up by the exposed mother ramet roots and then translocated to all the mother and daughter ramet tissues. As indicated by the analysis from high-resolution transmission electron microscopy and X-ray absorption near-edge structures, in addition to CeO2 NPs, CePO4, Ce(III) acetate, and Ce(III)-cysteine were found in the roots, and CePO4 was present in the rhizosphere soil. The Ce species in the rhizosphere soil decreased the rhizosphere microbial diversity, but stimulated the relative abundance of specific plant growth promoting rhizobacteria. These results provide new insights for understanding the benefits and sustainable applications of NPs.