The genus Youngia Cass. is taxonomically complex and widely distributed in East Asia. Despite the high diversity of species, only two species, Youngia japonica (L.) DC. and Youngia longiflora (Babc. & Stebbins) C.Shih, are currently found in Korea. Among them, Y. longiflora was once recognized as a subspecies of Y. japonica. However, based on chloroplast and nuclear DNA sequences, as well as morphology, Y. longiflora was found to be a distinct species. Here, the two Korean Youngia species were analyzed using scanning electron microscope and light microscope for chromosome number, pollen, cypselae, and leaf micromorphological characters to evaluate if the examined characters are informative for taxonomy. Pollen morphology is described, and the micromorphological characters of Y. longiflora are described for the first time. Cypselae and pollen surface ornamentation, as well as trichome morphology and stomatal size varied between the two species. Y. japonica had longer chromosomes than Y. longiflora, while other chromosomal characters including the localization of the NOR (nucleolar organizer region) were similar. The present micromorphological and cytological results are of great taxonomic value for Youngia species identification in Korea.

中文翻译：

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使用光学和扫描电子显微镜对 Youngia japonica 和 Youngia longiflora 进行微形态学和细胞学比较。

Youngia Cass属。分类复杂，广泛分布于东亚。尽管物种多样性很高，但只有两种，Youngia japonica (L.) DC。和Youngia longiflora (Babc. & Stebbins) C.Shih，目前在韩国发现。其中，Y. longiflora曾被确认为Y. japonica的一个亚种。然而，根据叶绿体和核 DNA 序列以及形态学，长叶耶尔森被发现是一个独特的物种。在这里，两位韩国Youngia使用扫描电子显微镜和光学显微镜分析物种的染色体数目、花粉、cypselae 和叶微形态特征，以评估检查的特征是否为分类学提供信息。描述了花粉形态，首次描述了长花野蔷薇的微形态特征。Cypselae 和花粉表面装饰，以及毛状体形态和气孔大小在两个物种之间有所不同。Y. japonica具有比Y. longiflora更长的染色体，而其他染色体特征包括 NOR（核仁组织区）的定位是相似的。目前的微形态学和细胞学结果对Youngia具有重要的分类学价值 韩国的物种鉴定