Antioxidant Systems Response, Mineral Element Uptake and Safe Utilization of Polygonatum Sibiricum in Cadmium-Contaminated Soil

Abstract Chinese herbal medicine is widely cultivated in southwest China where the soil cadmium (Cd) contamination of farmland is more serious than that in the whole of China. In this study, Polygonatum sibiricum were exposed to Cd at the concentrations of e− 1, e0, e2, and e4 mg·kg− 1 for up to 30,60, and 90 days and their physiological stress responses, Cd and mineral element uptake, antioxidant enzyme activities, and content changes of pharmaceutical ingredients (polysaccharides) were analyzed to decipher the feasibility of safety use in Cd contaminated soil. Results showed that the activity of antioxidant enzymes (SOD, POD, and CAT) of the aboveground part was enhanced in response to Cd stress after 90 d. Compared with the control, the underground part mobilizes non-enzymatic systems to facilitate the synthesis of polysaccharides (PCP1, PCP2) with antioxidant properties to cope with Cd stress. Mineral elements (P, K, Ca, Mg, Fe, Cu, and Zn) were significantly changed after 90 d of cultivation. In particular, the changes in iron and zinc contents were significantly correlated with the activities of SOD and POD. The soil Cd safety thresholds value for Polygonatum sibiricum is e0 mg·kg− 1, under which concentration the stimulation of Cd promotes polysaccharides synthesis and biomass growth.