Carbon ion beam-induced radiation hormesis in Bupleurum chinense DC.: Insights from growth, physiological, and metabolomic analyses for increased bioactive substances

• The yield of B. chinense remained stable after CIB pretreatment, even though seedling growth was temporarily suppressed. • The antioxidant system and photosynthetic system play crucial roles in the ROS-mediated stress priming and radiation hormesis of B. chinense. • Pretreatment with 50 Gy of CIB significantly increased total flavonoids, saikosaponins a and c, and several pharmacologically active substances in B. chinense. • Metabolomics revealed the reprogramming of flavonoid and terpenoid biosynthesis in B. chinense induced by CIB radiation. • CIB pretreatment represents a promising and environmentally friendly approach to enhance secondary metabolites in medicinal plants. Bupleurum chinense DC ( B. chinense ) is an important medicinal plant widely used in Asian countries. However, the efficacy of its medicinal components has medicinal components during the domestication process from wild to cultivated lines. Studies have shown that appropriate stress, such as ionizing radiation, can promote the accumulation of metabolites in medicinal plants. Nevertheless, the effects of ionizing radiation on B. chinense remains unclear. In this study, we systematically investigated the stimulatory effect of carbon ion beams (CIB) pretreatment on the growth, physiology, and accumulation of secondary metabolites in B. chinense . Although CIB irradiation inhibited the seed germination and survival rates, by the age of 4 months, the plant height and leaf area of the irradiated group had recovered to the levels comparable to the control. The enhanced growth performance during later developmental stages may be attributed to radiation hormesis and ROS-mediated regulation in antioxidant system and the photosynthetic system. One and two years after irradiation at doses of 50 and 100 Gy, no significant differences in root biomass were observed compared to the control group. Metabolically, the content of total flavonoid, saikosaponin a and saikosaponin c were significantly increased following 50 Gy irradiation. Further metabolomic analysis revealed that intermediate metabolites in the flavonoid and terpenoid biosynthetic pathways were significantly up-regulated in the 50 Gy irradiation group. Compounds with pharmacological activity also accumulated in large quantities after irradiation. These results suggest that pretreatment with 50 Gy CIB irradiation could serve as a potential method to promote the accumulation of secondary metabolites in B. chinense . This finding provides strong support for the application of physical radiation technology to enhance the production of secondary metabolites in medicinal plants, offering new avenues for the cultivation of high-quality Chinese herbal medicines.