中国花楸属单叶类群叶脉序特征研究

Leaf venation characteristics of simple-leaved taxa of Sorbus in China

关键词:  苹果亚科, 蔷薇科, 叶脉序特征, 形态分类, 聚类分析

Key words:  Maloideae, Rosaceae, leaf venation characteristics, morphology classification, cluster analysis

摘要:

中国花楸属单叶类群(24种)包含落萼组与冠萼组,亦有学者将其分为两个属(白花楸属和水榆属)或合并成为一个属(白花楸属)。由于其花序和果实的高度相似性,长期以来分类地位具有争议,而叶脉序特征在花楸属单叶类群中的分类作用尚不明确。因此,该研究以国产花楸属落萼组的13个物种和冠萼组的7个物种作为研究对象,以清净法制作标本对叶脉序特征进行观测研究,辅助部分叶形态特征进行主成分分析及系统聚类分析。结果表明:(1)中国单叶花楸在叶脉构架上存在一些共性:脉型都为羽状脉、网眼发育情况中等、间二级脉频度在每个粗二级脉间区少于一条。(2)不同物种的粗二级脉构架及对数、有无细二级脉、粗二级脉与主脉夹角的大小、二级脉间三级脉结构、盲脉分支情况、锯齿类型、叶片大小等性状存在一定差异。(3)冠萼组和落萼组组间的脉序特征存在较大的相似性,如粗二级脉构架、叶片大小、盲脉分支情况等多个脉序特征组间存在交叉,基于脉序特征的系统聚类结果不支持冠萼组和落萼组的划分。综上结果可知,叶脉序特征虽然无法作为冠萼组和落萼组的分组依据,但可以为部分单叶花楸的分类提供依据。

Abstract:

The simple-leaved taxa of Sorbus in China(24 species)include Sorbus sect. Aria and Sorbus sect. Micromeles. Some taxonomists divided it into two genera(Aria and Micromeles)or merged into one genus(Aria). Because of the high similarity of inflorescence and fruit, the taxonomic status has been controversial. However, the taxonomic value of leaf venation characteristics of simple-leaved taxa of Sorbus was still unclear. Therefore, 13 species of sect. Micromeles and 7 species of sect. Aria in China were investigated in this study. Cleaning specimen preparation was adopted for the leaf venation characteristics observation. The principal component analysis and cluster analysis were carried out based on leaf venation characteristics mainly and partial leaf characters. The results were as follows:(1)The simple-leaved taxa of Sorbus had identical vein framework, the veins of all samples were pinnate, the present condition of areolation was moderate developed, the frequency of intersecondary was less than one per intercostal in all species.(2)There were some differences among different species in major secondary vein framework and numbers, present minor secondary veins or not, major secondary angle to midvein, intercostal tertiary vein fabric, branches of freely ending veinlets, serrate type, laminar size, etc.(3)There were great similarities and multiple venation characteristics crossed between the sect. Aria and sect. Micromeles. For example, major secondary vein framework, laminar size, branching of freely ending veinlets etc. The result of systematic clustering based on leaf venation characteristics did not support the division of the sect. Aria and the sect. Micromeles. The results indicate that the leaf venation characteristics can not be used as the evidence to divide the sect. Aria and the sect. Micromeles into two groups, however, the leaf venation characteristics can be used as the evidence for classification of some simple-leaved taxa of Sorbus.