Abstract

Ligusticum chuanxiong Hort. is an important medicinal plant. Its dried rhizomes are used in traditional Chinese medicine (TCM) and have demonstrated significant efficacy in treating cardiovascular and cerebrovascular diseases. However, L. chuanxiong is a cadmium hyperaccumulator, which leads to cadmium concentrations in its medicinal rhizomes that often exceed the safe limit for medicinal materials. This property not only impedes the synthesis and accumulation of the plant's own active compounds but also triggers export bans or rejections, resulting in substantial economic losses. Building on our previous work in which three cadmium-tolerant microbial strains were isolated from the L. chuanxiong root system, this study aims to evaluate their efficacy in mitigating cadmium stress. Specifically, we investigated their ability to alleviate growth inhibition in the plant, reduce cadmium uptake, and explore their underlying tolerance mechanisms. This study employed a hydroponic system to conduct co-culture experiments with these microbial strains. Under cadmium stress (20 mg · L ^⁻¹, Group M), L. chuanxiong exhibited significant growth inhibition, root browning to dark brown or black, and increased malondialdehyde (MDA) content in leaves and roots. Cadmium stress induced oxidative damage and activated the antioxidant system (elevated CAT, POD, SOD in leaves; POD in roots). In contrast, co-culture with cadmium-tolerant strains (B90, F24, F38) alleviated growth inhibition. MDA content and CAT activity in leaves showed no significant increase, while POD and SOD activities were higher than in the CK group but significantly lower than in the M group, indicating reduced oxidative stress. All three strains significantly reduced cadmium content in shoots and roots, with variations among strains and plant parts. F38 decreased root cadmium by 54.72% and promoted cadmium translocation to shoots, whereas F24 reduced shoot cadmium by 40.27%. B90 demonstrated stronger efficacy in enhancing plant cadmium tolerance. Overall strain performance ranked as F38 > F24 > B90 in alleviating cadmium toxicity and promoting plant growth. In conclusion, these root-derived cadmium-tolerant strains effectively mitigate cadmium stress and reduce accumulation in medicinal rhizomes, providing valuable microbial resources and microecological strategies for ensuring the safety of medicinal plants.