Variation of leaf morphological and effective components of Eucommia ulmoides natural female population and its response to climatic factors

Abstract Eucommia ulmoides Oliv. is a significant medicinal and economically valuable tree species endemic to China. Female E. ulmoides plants are particularly prized for their fruits and seeds, which serve as important industrial, medicinal, and oil resources, offering a longer industrial chain and higher economic value compared to male plants. However, the morphological variation in leaves among natural female populations, the dynamics of pharmacologically active compounds, and their interactions with climatic and geographical factors remain poorly characterized. In this study, we examined five leaf morphological traits (e.g., leaf length, leaf width) and quantified twelve bioactive compounds in 126 mature E. ulmoides individuals from 10 populations across four provinces. Among the analyzed compounds, six major constituents chlorogenic acid (CGA), asperuloside (ASP), aucubin (AU), geniposidic acid (GPA), rutin (RT), and isoquercitrin (IQ) accounted for 96.25% of the total active ingredient content, while the remaining six minor components collectively represented only 3.75% (each < 0.1%). The six major compounds exhibited substantial variability, with coefficients of variation ranging from 36.67% (CGA) to 92.56% (AU) and Shannon diversity indices spanning from 1.61 (RT) to 2.01 (CGA). Significant inter-population differences were detected, with explanatory power values (\(\:{\widehat{P}}^{2}\)) as follows: CGA (0.24), AU (0.34), GPA (0.84), ASP (0.52), RT (0.15), and IQ (0.40). Across populations and leaf phenotypic traits, chemical composition showed strong associations with perimeter, length, and shape index. Notably, GPA exhibited a positive correlation with CGA and AU but negative correlations with the other nine compounds, suggesting that its biosynthesis may regulate the accumulation of CGA, IQ, ASP, and RT. While individual climatic and geographical factors showed weak associations with leaf traits and bioactive compounds, their combined effects played a more substantial role in shaping phenotypic and biochemical variation. These findings provide mechanistic insights into how female E. ulmoides plants optimize morphological and biochemical traits in response to environmental heterogeneity. Moreover, this study provides a scientific foundation for optimizing male-to-female planting ratios, advancing precision cultivation, and promoting the high-value utilization of E. ulmoides resources.