Rhizosphere ecology and physiological regulation drive cadmium accumulation efficiency in Hylotelephium spectabile populations

Abstract

Understanding the rhizo-ecological characteristics and physiological responses to Cd stress provides insight into the intrinsic Cd accumulation mechanisms of Hylotelephium spectabile. Under Cd exposure, the LN population exhibited a growth advantage over HB, attributed to Cd-induced chlorophyll enhancement. LN showed significantly increased root secretion of acetic and malic acids under Cd stress, acidifying the rhizosphere and providing functional groups for Cd-OA complex formation. Consequently, water-soluble and acid-extractable Cd levels were higher in the LN rhizosphere than in the HB rhizosphere. The increased proportion of protein-integrated Cd and decreased phosphate-sequestered Cd in the stems, along with the opposite trend in the leaves, revealed a key mechanism for efficient Cd translocation in the LN. Rhizosphere urease and dehydrogenase activities in LN responded more positively to Cd stress than in HB, providing improved nutrient conditions for growth. Furthermore, Cd-induced Proteobacteria and Chloroflexi enrichment in the LN rhizosphere played essential roles in modulating root exudates, pH, and Cd bioavailability. Upregulated pathways related to lipid/amino acid metabolism, as well as genetic replication and repair, may underlie the superior Cd accumulation efficiency of LN compared with HB.