Earthworms Drive the Effect of La 2 O 3 Nanoparticles on Radish Taproot Metabolite Profiles and Rhizosphere Microbial Communities.

To promote the sustainable and safe application of nanotechnology employing engineered nanoparticles (NPs) in agroecosystems, it is crucial to pay more attention to the NP-mediated biological response process and environmental impact assessment simultaneously. Herein, 50 mg kg -1 La 2 O 3 NPs were added to soils without and with earthworms for cherry radish growth for 50 days to investigate the response changes of metabolites in radish above- and below-ground organs and rhizosphere bacterial communities. We found that La 2 O 3 NP exposure, especially with earthworms, notably increased the La bioavailability and uptake by taproots and eventually increased radish leaf sucrose content and plant biomass. The La 2 O 3 NP exposure significantly altered metabolite profiles in taproot flesh and peel tissues, and particularly La 2 O 3 NP exposure combined with earthworms was more conducive to La 2 O 3 NPs to promote radish taproot peel to synthesize more secondary antioxidant metabolites. Moreover, compared with the control, the La 2 O 3 NP exposure resulted in weaker and fewer correlations between rhizosphere bacteria and taproot metabolites, but this was recovered somewhat after the inoculation of earthworms. Altogether, our results provide novel insights into the soil-fauna-driven biological and biochemical impact of La 2 O 3 NP exposure on edible root crops and the long-term environmental risks to the rhizosphere microbiota in agroecosystems.