Sulfur fertiliser enhancement of Erigeron breviscapus (Asteraceae) quality by improving plant physiological responses and reducing soil cadmium bioavailability.

Erigeron breviscapus (Vant.) Hand.-Mazz. is an important medicinal plant; however, its quality is severely diminished by cadmium (Cd) pollution. Sulfur fertilisation can improve the production and application of E. breviscapus. This study examined Cd stress alleviation in the soil-plant system and determined the plant growth response after the application of sulfur fertiliser. The soil Cd concentration used in the treatments was 100 g·kg, and the sulfur fertiliser application rates were 0.1, 0.2, and 0.3 g·kg. Using pot experiments, we explored the impacts of high, medium, and low amounts of sulfur fertiliser on Cd accumulation and the quality and activity of E. breviscapus. The results showed that the application of sulfur fertiliser promoted Cd transformation to residual Cd under oxidation conditions, reducing Cd accumulation in E. breviscapus. Throughout the growth period, the application of sulfur fertiliser increased the soluble protein content and antioxidant enzyme activity, which alleviated Cd toxicity. The net photosynthetic rate, transpiration rate, intercellular CO concentration, chlorophyll level, and leaf width increased significantly. The biomass content of E. breviscapus also increased. Sulfur fertiliser improves the quality of herbaceous medicinal plants by reducing Cd accumulation and increasing scutellarin, chlorogenic, isochlorogenic acid B, and isochlorogenic acid C contents. A reasonable application of sulfur fertiliser is essential for improving E. breviscapus quality. This study provides a new method to reduce the ecological risk of planting herbaceous medicinal plants in Cd-contaminated soil.