Silicon-mediated cadmium mitigation and bioactive compound accumulation in Erigeron breviscapus: Root and shoot responses

Silicon (Si) is widely recognized for alleviating cadmium (Cd) stress in plants. However, the mechanisms by which Si coordinates root–shoot responses to sustain productivity and valuable bioactive compound production in cultivated medicinal crops under Cd stress remain elusive. Here, hydroponic and pot experiments combined with physiological, transcriptomic, and metabolomic analyses were conducted to investigate Si-mediated Cd stress mitigation in the cultivated medicinal crop Erigeron breviscapus . Under hydroponic experiment, compared with the Cd-alone treatment (+Cd), the application of Si (+Cd+Si) increased shoot biomass and scutellarin content by 54.5% and 57.5%, respectively. Although +Cd+Si increased the total shoot- and root- Cd accumulation by 12.9% and 23.1%, respectively, +Cd+Si reduced shoot Cd content by 26.9% related to +Cd. Mechanistically, Si suppressed Mg 2 + and Zn 2+ transporter genes and promoted phenylpropanoid/lignin biosynthesis in roots, contributing to lower root Cd content and altered Cd partitioning. In shoots, Si increased the proportion of Cd in the soluble fraction, consistent with enhanced vacuolar sequestration, restored photosynthesis efficiency, boosted antioxidant capacity, and stimulated scutellarin biosynthesis. Overall, Si-mediated Cd stress mitigation involves integrated root and shoot responses including modulated Cd uptake and distribution, vacuolar sequestration, antioxidant defense, and secondary metabolism. These findings reveal a mechanistic basis for sustaining productivity and valuable bioactive compound production in a cultivated medicinal industrial crop under Cd stress and highlight Si management as a potential strategy for improving the resilience of E. breviscapus cultivation in Cd-contaminated soils.