Spatial variation in chemical components of Rheum palmatum L. and climatic response characteristics

We investigated geographical variation in the chemical components of rhubarb (Rheum palmatum L.) and its response to multilevel climatic factors based on clustering and heap graph analysis. Results showed that rhubarb from Sichuan belonged to the free anthraquinone-double anthrone chemical type, while rhubarb from Gansu and Ningxia belonged to the anthraquinone chemical type. Pearson correlation analysis of the response relationships between multilevel climatic factors and rhubarb components showed that temperature and vapor pressure were key factors related to spatial variation in R. palmatum quality. Anthraquinones were positively correlated with mean monthly temperature from March to November and mean monthly water vapor pressure for the whole year, positively correlated with mean monthly sunshine from June to August, and negatively correlated with mean monthly precipitation from June to September. Free anthraquinones were negatively correlated with mean monthly water vapor pressure in the coldest season. Anthrones were negatively correlated with monthly temperature and negatively correlated with monthly water vapor pressure. These results implied that vapor pressure in the coldest season and monthly average temperature in the wettest season were important time windows and key factors affecting R. palmatum quality.