Divergent Physiological and Biochemical Responses of Roots and Shoots in Saposhnikovia divaricata to Cold Stress

Saposhnikovia divaricata is a renowned frigid zone herbal medicine primarily produced in Northeast China, which can survive cold winters due to its underground root system; however, the mechanisms underlying long-term cold stress are uncertain. Here, we aim to investigate its adaptive response to cold stress to determine whether specific cold tolerance strategies exist. In this research, we investigated changes in morphology and physiological metabolism under cold stress in Saposhnikovia divaricata using the Intelligent Artificial Climate Chamber setup for cold stress 10°C/5°C (day/night) and control 25°C/20°C (day/night). The results showed that cold stress resulted in a diminution of antioxidant enzyme activity, impairments in the membrane system, reductions in photosynthetic physiological parameters, and a decrease in shoot biomass. Roots under cold stress exhibited an increase in antioxidant enzyme activity, an increase in osmotic regulators, a tendency for metabolites to sustain primary growth, resulting in a diminution of secondary metabolites, and an approximately unchanged biomass. These studies indicate that Saposhnikovia divaricata adopts a tissue-specific resistance strategy under cold stress, with priority attached to supporting root survival, which lays the foundation for in-depth studies on the mechanisms of cold tolerance in Saposhnikovia divaricata.