Leaf Epidermal Micromorphology of the Korean Angelica (Apiaceae) and Its Taxonomic Implications

The genus Angelica L. (Apiaceae) is mainly distributed throughout the Northern Hemisphere and comprises approximately 110 species. Although several molecular phylogenetic studies have been conducted on this genus, the leaf micromorphology has not been sufficiently explored. In this study, we examined the leaf micromorphological characteristics of all the 16 Korean Angelica taxa using light and scanning electron microscopy. The results revealed considerable variation in the morphology of stomatal complexes, epidermal cells, and trichomes. Leaf epidermal cells were generally irregular in shape, exhibiting straight to curved, undulating, or sinuating anticlinal walls, and convex or flat periclinal walls. The leaves were either hypostomatic or amphistomatic, with the former being more frequent. In the amphistomatic taxa, stomata were more densely distributed on the abaxial surface than on the adaxial surface. Anomocytic stomata were predominant, although paracytic stomata were also observed in certain taxa. Simple trichomes were present in all studied taxa, except A. acutiloba. These micromorphological features provide valuable information for species identification and offer important taxonomic insights into this genus. Moreover, the observed variations in leaf micromorphology appeared to be closely related to environmental factors, suggesting that these traits reflect adaptive responses to habitat conditions.