国产秋海棠属(秋海棠科) 花粉形态及其分类学意义(英文)

Pollen morphology of Chinese Begonia (Begoniaceae) and its taxonomical significance

关键词:  扫描电镜，性状编码，非线性多维标度分析，塞缘，非单系类群

Key words:  SEM,characters coded,NMDS,margo,non-monophyletic groups

摘要:

秋海棠属是世界有花植物第六大属，是被子植物分类困难的类群之一，亟需增加形态性状的比较研究，以便于今后对该属开展分类学修订。该研究选取国产秋海棠属中较为常见的侧膜组、秋海棠组、单座组和二室组共21种，应用扫描电镜观察花粉微形态，探讨花粉形态对秋海棠属植物的分类学意义。结果表明：秋海棠属植物的花粉多为单粒花粉，辐射对称，等极，三孔沟，超长球形到长球形。选取9个稳定的花粉特征进行无序和不加权的性状编码，应用非线性多维标度分析对花粉特征矩阵进行聚类分析，结果支持这些组都不是单系类群需要重新修订，其中花粉边缘形状、极面观轮廓、萌发沟和花粉的外壁纹饰具有一定分类学意义，特别是塞缘特征具有重要的分类意义。根据塞缘特征可以将研究类群区分为2个类群：（A）无塞缘或塞缘光滑；（B）塞缘颗粒状。类群B中具规则颗粒状和精细颗粒状塞缘的种类聚在一起，而具粗糙颗粒状塞缘的种类位于类群A和B的中间，很可能是2个类群的过渡性状，这需要增加取样做进一步的研究。

Abstract:

Begonia L. is the sixth biggest genus of flowering plants in the world and a major genus in the family Begoniaceae. It is complicated in current section delimitation and more morphological characters are needed for critical revaluation within the genus. In present study，we selected 21 species from sections Coelocentrum，Begonia，Platycentrum and Reichenheimia of Begonia mainly distributed in China. Using the method of scanning electron microscopy (SEM)，the pollen morphology was carefully examined and its systematic significance was discussed. The results showed that the common palynological characters of studies taxa were exhibited as monads，radially symmetrical，isopolar，3-zono-colporate and perprolate to prolate. For non-metric multidimensional scaling (NMDS) analysis，nine stable pollen characters were selected and coded as unordered and unweighted. The results supported that these sections were not monophyletic groups and the useful palynological features for this study were the pollen sides，outline of the poles，colpus，exine ornamentation，and margo. According to the ornamentation of margo，the studied taxa can be divided into two groups：(A) without margo and psilate margo，(B) regulate，exquisitely regulate and coarsely regulate margo. In relation to Group B，the taxa with regulate and exquisitely regulate grains were gathered while the taxa with coarsely regulate margo were located between Group A and B. It indicated that the feature of margo was exhibited as a transition，from without margo and psilate margo，along coarsely regulate margo to exquisitely regulate. Therefore，it is worthy to pay more attention on the feature of margo and increase more taxa of the genus in further studies.