Anatomy of the vegetative organs as subsidy to the taxonomy of Geissospermum (Apocynaceae - Rauvolfioideae)

Abstract Considering the interspecific morphological similarities in Geissospermum and the difficulty of collecting fertile specimens of the genus, this work aimed to provide potential diagnostic anatomical characters for the group based on the analysis of vegetative organs. For this, stem and leaf samples of G. argenteum Woodson, G. laeve (Vell.) Miers, G. reticulatum A.H. Gentry, G. sericeum Miers, and G. urceolatum A.H. Gentry were collected from exsicates deposited at the herbaria HAMAB, INPA and MG and processed according to standard plant anatomy techniques. The studied species were then compared on a binary matrix of characters submitted to methods of grouping (UPGMA) to obtain a phenogram and, posteriorly, a dichotomous identification key. Our phenotype analysis showed that the most similar anatomically species are G. argenteum with G. sericeum, G. laeve with G. reticulatum, and G. urceolatum being the most distinct species in the genus. Our results show that the anatomy contributed to the identification of Geissospermum, even in the absence of reproductive organs. The epidermal cell shape, persistence of trichomes, brachycleral arrangement, contour and vascularization of the petiole were the most important features to the recognition of taxa within the taxa.

摘要
鉴于胶核木属（Geissospermum）存在显著的种间形态相似性，且该属可育标本采集难度较高，本研究旨在通过营养器官分析，为该类群提供潜在的诊断性解剖学特征。为此，本研究从HAMAB、INPA及MG标本馆馆藏的蜡叶标本中，采集了银叶胶核木（G. argenteum Woodson）、光叶胶核木（G. laeve (Vell.) Miers）、网脉胶核木（G. reticulatum A.H. Gentry）、绢毛胶核木（G. sericeum Miers）以及壶形胶核木（G. urceolatum A.H. Gentry）的茎、叶样品，并按照标准植物解剖学技术进行处理。随后，基于构建的性状二元矩阵，对供试物种开展比较分析，采用非加权组平均法（UPGMA）进行聚类分析以生成聚类图，并进一步构建二歧检索表。本次表型分析结果显示，解剖特征最为相似的类群为银叶胶核木与绢毛胶核木、光叶胶核木与网脉胶核木，而壶形胶核木为该属中解剖特征最为独特的物种。本研究结果表明，即便缺乏生殖器官，解剖学特征亦可有效用于胶核木属物种的鉴定。其中，表皮细胞形态、毛状体留存情况、brachycleral排列方式、叶柄轮廓及维管结构，是该属内类群识别的关键特征。