Abstract:

To screen germplasm resources of Astragalus membranaceus var. mongholicus with high environmental adaptability to Daqing City, Heilongjiang Province, seeds from six geographical sources, Yinchuan (Ningxia), Hohhot (Inner Mongolia), Qiqihar (Heilongjiang), Baoding (Hebei), Shuyang (Jiangsu), and Taiyuan (Shanxi)—were sown in 2020 at the experimental base in Daqing. The site features a temperate continental monsoon climate, with an average annual temperature of 4.2℃, annual precipitation of 427.5 mm, and chernozem soil. After four years of cultivation, functional leaves from mature plants were collected. Using paraffin sectioning, 14 leaf anatomical traits were measured, including midvein diameter, midvein vessel diameter, leaf thickness, epidermal thickness, cuticle thickness, palisade tissue thickness, spongy tissue thickness, stomatal length, and stomatal width. Derived indices such as palisade-to-spongy ratio (P/S), cell tension ratio (CTR), and sponge ratio (SR) were also calculated. Principal component analysis (PCA) and hierarchical clustering were employed to elucidate anatomical differentiation among seed sources and their environmental adaptation under uniform growing conditions. Key findings include: (1) significant genetic divergence in leaf anatomy was observed among seed sources. Core adaptive traits included P/S ratio, CTR, palisade tissue thickness, midvein diameter, and leaf thickness. The Qiqihar (Heilongjiang) source exhibited superior performance, with palisade tissue thickness of (96.03±3.73) μm, P/S ratio of (3.84±1.14), and CTR of (63±0.4)%, all significantly higher than other sources. In contrast, the Hohhot (Inner Mongolia) source showed the lowest values for these traits (palisade tissue thickness: 72.25±7.43 μm; P/S ratio: 1.52±0.55; CTR: 37±0.4%). (2) PCA extracted four principal components, collectively accounting for 85.12% of the total variance. PC1 (44.34% variance) was heavily loaded with P/S ratio (0.93) and CTR (0.92), reflecting the synergistic function of mesophyll structure in light capture and water use. PC2 (20.50%) was associated with midvein diameter (0.87) and vessel diameter (0.92), indicating vascular transport efficiency. PC3 (11.79%) was linked to upper (0.86) and lower (0.76) epidermal thickness, representing protective mechanisms. PC4 (8.49%) correlated with leaf thickness (0.71) and stomatal length (-0.85), suggesting a trade-off between leaf thickness and stomatal size regulation. (3) Environmental adaptability rankings, consistent with cluster analysis, based on PCA composite scores, were as follows: Qiqihar (0.98) > Shuyang (0.10) > Baoding (0.06) > Yinchuan (-0.02) > Taiyuan (-0.15) > Hohhot (-0.97). Hierarchical clustering (Euclidean distance = 5) grouped the sources into three adaptability categories: Group I (Qiqihar, Shuyang)-high adaptability; Group II (Baoding, Yinchuan, Taiyuan)-moderate adaptability; Group III (Hohhot)-low adaptability. This study clarifies the genetic differentiation in leaf anatomical traits of A. membranaceus var. mongholicus and identifies key adaptive indicators, providing an anatomical basis for selecting superior germplasm in Northeast China and similar ecological regions. It also offers theoretical support for assessing the adaptability of medicinal plants introduced across different geographic areas.

Key words: Astragalus membranaceus var. mongholicus, geographic provenances, leaf anatomical structure, environmental adaptability, drought resistance, principal component analysis, cluster analysis, core adaptive indicators, paraffin sectioning technique