Comparative pollen morphological analysis in the subgenera Passiflora and Decaloba

ABSTRACT The genus Passiflora is the most diversified of the Passifloraceae, and its palynology presents wide morphological variability. The objective of the study was to evaluate the pollen morphology of 18 Passiflora species in order to identify informative pollinic characteristics to contribute to the taxonomic classification of the genus. The morphology of the pollen grains and the exine structure were investigated using light microscopy and scanning electron microscopy. Differences in the pollen morphology were found in the studied species, mainly in terms of shape, pollen aperture and ornamentation pattern of the exine. Most of the species belonging to the subgenus Passiflora presented ornamented 6-syncolpate pollen grains with an oblate-spheroidal shape and an exine with large lumens. In the subgenus Decaloba the pollen grains were 6-colporate, 12-colpate and 12-colporate, with subprolate to prolate-spheroidal shape, as well as an exine with smaller lumen size and few ornamented. The pollen morphology of the species of the subgenera Passiflora and Decaloba has shown palynological characteristics that have specific diagnostic value, thus allowing a better understanding of the taxonomy of the genus Passiflora.

摘要：西番莲属（Passiflora）是西番莲科（Passifloraceae）中物种多样性最高的类群，其孢粉学特征具有丰富的形态变异。本研究以18种西番莲属植物为研究对象，对其花粉形态及外壁结构进行分析，旨在筛选出具有分类学参考价值的孢粉特征，为该属的分类学修订提供依据。研究采用光学显微镜与扫描电子显微镜开展观测，结果显示供试物种的花粉形态存在显著差异，主要体现在花粉形状、萌发孔类型及外壁纹饰模式三个方面。隶属于西番莲亚属（subgenus Passiflora）的多数物种，其花粉为具纹饰的6合沟花粉，形状呈扁球形-近球形，外壁具较大的网眼。而复叶亚属（subgenus Decaloba）物种的花粉则包含6孔沟、12合沟及12孔沟三种类型，形状呈近长球形至长球形，外壁网眼尺寸更小且纹饰相对稀疏。综上，西番莲亚属与复叶亚属物种的花粉形态特征均具备独特的分类鉴定价值，有助于进一步明晰西番莲属的分类系统。