Comparative seed morphology of Rhododendron (Ericaceae) species on the Korean Peninsula

Taxonomic studies of Rhododendron have largely focused on palynology, molecular phylogeny, and external morphology, with only limited attention paid to the areas of seed morphology and seed surface micromorphology. This study investigated the morphological characteristics of seeds from ten East Asian Rhododendron species to assess their potential taxonomic utility. Morphological traits were measured and surface images were captured by light and scanning electron microscopy to analyze the micro-morphological characteristics of the seeds. The analysis revealed that most of the included species bear small, light, elliptical seeds in brown tones, while basal and apical wings were observed in R. aureum and R. brachycarpum. Furthermore, a striate surface pattern was a commonly observed characteristic, but the structure of the anticlinal ridge varied among the species. The seed size, weight, color, shape, presence of appendages, and surface micromorphological characteristics can be considered for species identification within the genus. This study provides a detailed presentation of the micromorphological variation in Rhododendron seeds, thereby offering foundational data for species identification and taxonomic research.