enhances growth and cadmium tolerance via modulating root architecture and cadmium speciation in contaminated environments.

Introduction: Dark septate endophytes (DSEs) commonly colonize plant roots in heavy metal-polluted habitats, but little is known about the potential mechanisms driving medicinal plants to adapt to heavy metal-polluted environments. Here, we investigated the growth of strains and their enhancing of cadmium (Cd) tolerance and growth in in Cd-contaminated soil.

Methods: First, we tested the Cd resistance of by culture. Then, we studied the performance of inoculated with in Cd-contaminated soil.

Results: It was found that possessed a capacity to accumulate Cd in its mycelium. The Cd-contaminated environment increased the content of melanin and osmotic substances and reduced the proportion of the highly toxic chemical form of Cd in the mycelium of . In Cd-contaminated soil, effectively colonized plant roots and improved soil nutrients and the growth of . The -inoculated treatment significantly increased the contents of effective nitrogen (37.74%), urease (31.55%), and alkaline phosphatase (29.82%) in 10 mg Cd/kg soil, compared with the non-inoculated treatment. More importantly, inoculation increased root biomass for 5 and 10 mg Cd/kg soil by 42.35% and 30.21%, respectively, in comparison to non-inoculated control. Inoculation with reduced the proportion of the highly toxic chemical form of soil Cd, and reduced the accumulation of Cd in plants, especially in the roots.

Discussion: These results indicated that DSEs have a positive influence on the growth and Cd tolerance of , and reduce the biological toxicity of soil Cd. Therefore, exploitation and utilization of DSEs resources might be a new method for improving the cultivation of medicinal plants and soil microenvironment in heavy metal-contaminated areas.