Silicon nanoparticles and jasmonic acid synergistically enhance cadmium phytoextraction by Sedum alfredii via coordinated metal acquisition and stress tolerance.

Cadmium (Cd) phytoextraction requires efficient metal acquisition and translocation without compromising plant growth and detoxification. We investigated the effects of silicon nanoparticles (Si-NPs) and jasmonic acid (JA), applied alone or together, on Cd phytoextraction by Sedum alfredii. The combined treatment increased shoot biomass and total Cd accumulation by 32.6% and 67.4%, respectively. Si-NPs-containing treatments increased rhizosphere available Cd by 5.4-5.9%, promoted Cd uptake and root-to-shoot translocation, and induced Cd- and Si-transport-related genes. JA strengthened antioxidant enzyme activities. The combined treatment further increased phytochelatin and glutathione levels by 152% and 48.7%, respectively, while reducing malondialdehyde by 38.5%. These responses indicate enhanced thiol-mediated detoxification and oxidative protection. Metabolomic and microbiome analyses further revealed compartment-specific responses. The rhizosphere was associated with Cd-mobilization-related metabolites and enrichment of potentially beneficial genera, including Polycyclovorans and Ramlibacter. In contrast, leaves showed enhanced sulfur-thiol metabolism, redox regulation, and secondary metabolism. Multiblock integration linked Cd phytoavailability and accumulation with detoxification and biomass production. Overall, Si-NPs and JA exhibited asymmetric functional complementarity, integrating enhanced Cd acquisition and transport with thiol-centered detoxification and growth maintenance. This accumulation-compatible tolerance strategy provides a mechanistic framework for improving assisted Cd phytoextraction by coordinating Cd flux with whole-plant detoxification capacity.