Microalgae enhance cadmium accumulation in Perilla frutescens: Root structural adaptation and secretion-mediated detoxification

Ying RenYuying SuJinfeng LiHui ZhangYumeng YangYuan Yuan LiJuan ChenXiaohui PangZheng Zhang^*Jianping Han^*

• Chinese Academy of Medical Sciences & Peking Union Medical College Institute of Medicinal Plant Development, Beijing, China

Cadmium (Cd) phytoremediation is often constrained by the low accumulation capacity and limited stress tolerance of most plant species. This study demonstrated that microalgae treatment could improve the Cd phytoextraction capacity of Perilla frutescens. Under Cd stress conditions, microalgae supplementation significantly enhanced total plant biomass by 37.43% while increasing Cd accumulation by 20.72% in roots, 25.87% in stems, and 112.29% in leaves relative to Cd-only treatment. Further investigation revealed that these improvements were closely associated with microalgae-induced physiological adaptations in roots, characterized by elevated peroxidase activity, reduced superoxide anion generation, and mitigated lipid peroxidation. Microalgae treatment also promoted Cd retention in root cell walls, with hemicellulose I showing a 166.37% increase in Cd binding (p <0.05). Ultrastructural and spectroscopic analyses indicated that this enhancement likely stems from optimized root cell wall structure and increased functional group activity. Additionally, microalgae dramatically altered root exudate composition, particularly increasing secretion of metal-chelating and antioxidant compounds such as ferulic acid, artemisinic acid, and dihydroartemisinin, whose concentrations were positively correlated with plant Cd accumulation.Together, these findings revealed how microalgae modulated root structural and metabolic traits to enhance Cd accumulation and tolerance in Perilla frutescens, supporting the application of microalgae-assisted phytoremediation in complex environmental settings.