Laboratório de Botânica Estrutural, Departamento de Ciências Biológicas, Universidade Estadual do Centro-Oeste-UNICENTRO-Campus CEDETEG, Guarapuava, Brazil.
Programa de Pós-graduação em Biologia Evolutiva, Universidade Estadual do Centro-Oeste-UNICENTRO-Campus CEDETEG, Guarapuava, Brazil.
Protoplasma. 2019 Jul;256(4):923-939. doi: 10.1007/s00709-019-01350-w. Epub 2019 Feb 4.
Passifloraceae shows a huge variability of pollen wall characteristics, most still little described. Passiflora is the largest genus with about 580 species with tropical distribution. Few studies in palynological approaches have described the intine layer which can fill existent gaps. Passiflora L. present four subgenera, from which Passiflora, Astrophea, and Decaloba were described in this study. The pollen wall variations were poorly studied, with the objective of describing the morphological and histochemical structure of Passiflora sporoderm that occurs in South America, aims to supply more pollen wall characters in some contexts. Besides the inference of evolutive trends, we described the number of apertures, type, reticule, and variations of the morphology and sporoderm and we related them with possible evolutive trends for the group. As a result, the pollen grains were not far from the patterns found by the literature, with exceptions. The species of the subgenus Passiflora have fused colpi, varying from 6 to 12 colpi, with type 2-reticulate exine. The species of the subgenus Astrophea have colporus and the species of Decaloba varied as the type of aperture, in which a new type of exine to be considered was found: the type 3. The subgenus Passiflora showed the thickest intine, slim endexine, and absent foot layer. While the species that belong to the other subgenera present a slim intine, the endexine is thick and the foot layer is continuous, among other variable characteristics. The size of the pollen grain seems to be related to the thickness of the intine, and consequently, related to possible pollinators. Through the cluster analysis, we reinforce the affinity of the species to its respective subgenus. To conclude, the analysis of the ultrastructure of the sporoderm and external morphology would be useful for an almost complete interpretation of the variations occurring in the genus, giving more information that the subgenus Passiflora is apomorphic when compared to the other two. The pollen wall characters should be considered on the interpretation of natural history, as well as the phylogenetic relationships of the family, mainly in the Passiflora genus, that has a large number of species distributed across the Neotropical regions.
西番莲科显示出花粉壁特征的巨大变异性，其中大多数仍描述甚少。西番莲属是最大的属，约有 580 种，分布于热带地区。在花粉学方法的少数研究中，曾描述过可以填补现存空白的内纹饰层。西番莲属有四个亚属，本研究描述了其中的三个亚属：西番莲亚属、安石榴亚属和德卡洛巴亚属。花粉壁的变化研究甚少，本研究的目的是描述发生在南美洲的西番莲花粉壁的形态和组织化学结构，旨在为某些情况下提供更多的花粉壁特征。除了推断进化趋势外，我们还描述了花粉粒的纹饰、形态和花粉壁的孔数、类型、网眼以及变化，并将其与该组可能的进化趋势联系起来。结果，花粉粒与文献中发现的模式相差不远，但也有例外。亚属西番莲的花粉粒具融合的萌发沟，萌发沟数为 6-12 条，具 2 型网状外壁；安石榴亚属的花粉粒具孔沟；德卡洛巴亚属的花粉粒具孔的类型变化，其中发现了一种新的外壁类型：3 型。亚属西番莲的内纹饰层最厚，外壁内层最薄，无外壁底层。而属于其他两个亚属的种则具有薄的内纹饰层，厚的外壁内层和连续的外壁底层等可变特征。花粉粒的大小似乎与内纹饰层的厚度有关，因此与可能的传粉者有关。通过聚类分析，我们加强了种与其相应亚属的亲缘关系。总之，对花粉壁超微结构和外部形态的分析有助于对该属发生的变异进行几乎完整的解释，提供更多的信息，表明与其他两个亚属相比，西番莲亚属是特化的。花粉壁特征在解释自然历史和科的系统发育关系时都应该被考虑，特别是在西番莲属，该属有大量的种分布在新热带地区。
