Tissue-specific distribution and translocation of cadmium in Populus and Paulownia

Soil contamination with multiple heavy metals necessitates phytoremediation strategies that leverage plant-specific partitioning mechanisms. This study comparatively assessed the uptake, translocation and compartmentalization of cadmium (Cd), zinc (Zn) and copper (Cu) in two fast-growing trees, Populus and Paulownia, via a combined field investigation in a mining area and a controlled pot experiment. Results revealed Populus functioned as an active accumulator, exhibiting higher bioaccumulation (BAFs) and translocation (TFs) factors for Cd, with significant enrichment in leaves and bark. In contrast, Paulownia acted as an excluder-stabilizer, primarily retaining Cd in roots while accumulating more Cu in stems. Internal stem Cd distribution decreased from base to apex in both species, with bark identified as a major long-term sink. These findings underscore the potential of Populus for Cd phytoextraction and of Paulownia for Cu stabilization and revegetation, providing a scientific basis for selecting appropriate species for targeted phytoremediation in multi-metal-contaminated environments.