Spatial variation in saponin content and climatic response characteristics

Ultra-violet-visible spectrophotometry (UV-VIS) was applied to determine saponin content in Pseudostellaria heterophylla in four main producing areas to analyze their spatial variation rules. Pearson correlation was used to analyze the response relationship between multi-scale climatic factors and saponin content. Results showed significant spatial variation in saponin content, with high-content regions in Jiangsu and Anhui provinces and low-content regions in Guizhou and Fujian provinces. Saponin content was strongly positively correlated with annual average solar radiation, while negatively correlated with annual average humidity and annual precipitation. Furthermore, saponin content was positively correlated with maximum temperature of the warmest month, while negatively correlated with mean temperature in the coldest quarter. Monthly mean solar radiation and monthly mean temperature were key factors for saponin content in P. heterophylla. Saponin content was strongly positively correlated with monthly average solar radiation from January to December and positively correlated with monthly mean temperature from May to September, but negatively correlated with monthly mean temperature from January to April and November to December. Results indicated that solar radiation is a vital climate factor for the spatial variation of saponin content. High-solar radiation, high temperature differences, and low precipitation and humidity were conducive to saponin accumulation in P. heterophylla.