Department of Plant Sciences, Quaid-I-Azam University, Islamabad, Pakistan.
Department of Botany, Qurtuba University of Science and Information Technology, Peshawar, Pakistan.
Microsc Res Tech. 2019 Jul;82(7):1021-1031. doi: 10.1002/jemt.23249. Epub 2019 Mar 12.
The present study is insight into pollen morphology for characterizing species and their utility in the taxonomic separation of certain taxa of subfamily Nepetoideae (Lamiaceae) from Pakistan. The pollen micromorphology of 11 species of the Nepetoideae was analyzed and documented using light microscopy and scanning electron microscopy (SEM) for both qualitative and quantitative characteristics. Most species have hexazonocolpate pollen grains but trizonocolpate and tetrazonocolpate pollen with circular and oval amb were also rarely observed in Mentha spicata. The basic pollen shape in most of the studied species was subspheroidal but prolate grains were also observed in M. spicata, S. coccinea, and S. plebeia. The exine sculpturing of Nepetoideae pollen was taxonomically very informative particularly at subfamily level. Observations of exine sculpturing with SEM revealed various types of pollen grains: reticulate, bireticulate, microreticulate, perforate, aerolate, and gammate. The bireticulate type further subdivided into three subtypes based on the number of secondary lumina in each primary lumen and is characterized by varying characteristics of the secondary reticulum and primary muri. A significant variation was observed in colpus surface ornamentation. The maximum polar diameter was found in O. americanum (58 ± 5.8 μm) and the maximum equatorial diameter observed in O. basilicum (50.25 ± 1.37 μm). Pollen features of the studied species were discussed and compared based on the current taxonomical concepts. The results showed that pollen traits of the subfamily Nepetoideae was found significant to classify the taxa. Furthermore, pollen features provide additional evidence to distinguish macromorphologically similar taxa from each other.
本研究深入探讨了花粉形态学在特征描述物种中的作用，以及在巴基斯坦唇形科 Nepetoideae 亚科某些分类群的分类分离中的应用。利用光学显微镜和扫描电子显微镜（SEM）对 Nepetoideae 的 11 种植物的花粉微形态进行了分析和记录，以获得定性和定量特征。大多数物种具有六沟花粉，但也很少观察到薄荷（Mentha spicata）中具有三沟和四沟花粉，且沟呈圆形和椭圆形。在大多数研究物种中，基本花粉形状为近球形，但也观察到了长球形花粉，如薄荷（M. spicata）、红轮齿唇花（S. coccinea）和糙苏（S. plebeia）。 Nepetoideae 花粉的外壁纹饰在分类上非常有信息量，特别是在亚科水平上。利用 SEM 观察外壁纹饰可以揭示各种类型的花粉粒：网状、双网状、微网状、穿孔状、气室状和颗粒状。双网状类型进一步根据每个初级管腔中的次级管腔的数量分为三个亚型，其特征是次级网状和初级壁的特征不同。在沟脊表面纹饰上观察到了显著的变化。最大极径出现在美洲薄荷（O. americanum）（58±5.8μm），最大赤道径出现在罗勒（O. basilicum）（50.25±1.37μm）。根据当前的分类概念，对研究物种的花粉特征进行了讨论和比较。结果表明，亚科 Nepetoideae 的花粉特征对于分类具有重要意义。此外，花粉特征为区分宏观形态相似的分类群提供了额外的证据。
