Exposure of cerium oxide nanoparticles to the hyperaccumulator Sedum alfredii decreases the uptake of cadmium via the apoplastic pathway.

Cadmium (Cd) is harmful to the environment and threatens human health. With the increasing use of cerium oxide nanoparticles (CeO 2 NPs) in extensive industries, investigating the combination of CeO 2 NPs and plants has attracted research interests for phytoremediation. Here, we explored the effects of CeO 2 NPs on Cd uptake, transport and the consequent Cd accumulation in Sedum alfredii. Exposure of 50 or 500 mg L−1 CeO 2 NPs alone had no apparent damaging effects on plant growth. However, upon Cd condition, the consistent CeO 2 NPs decreased Cd concentrations in the roots and shoots by up to 37%. Furthermore, the application of a metabolic inhibitor revealed that CeO 2 NPs mainly decreased the Cd uptake in roots by the apoplastic pathway. Simultaneously, CeO 2 NPs accelerated the development of Casparian strips (CSs) and suberin, which was further proven by the elevated expression levels of genes associated with their formation, SaCASP , SaGPAT5, SaKCS20 and SaCYP86A1. Compared to CeO 2 NPs added alone, the concurrent Cd decreased the Ce contents in the roots and altered its translocation from root to shoot. Taken together, both CeO 2 NPs and Cd influence the interactional uptake of both chemicals in roots of S. alfredii mainly via the apoplastic pathway which is primarily regulated by the development of CSs and suberin. [Display omitted] • CeO 2 NPs accelerate the endodermal apoplastic barriers development. • Ce contents are promoted by Cd in shoot at low level of CeO 2 NPs. • CeO 2 NPs mainly decrease Cd accumulation in HE via apoplastic pathway. • CeO 2 NPs reduce the phytoremediation efficiency of Cd by Sedum alfredii. [ABSTRACT FROM AUTHOR]