A Review of the Papaveraceae Family Based on the Multidisciplinary Study of Pollen Grain: Ultrastructure and Ontogeny

In this paper, the Papaveraceae family is analyzed from the perspective of molecular phylogeny and pollen ultrastructure carried out by our research group and new data is added until all its subfamilies and tribes are completed. The work focuses on all ontogenetic aspects of the ultrastructure of the wall and pollen aperture, its nutritional tissue, and also the presence of multilamellar cytoplasmic bodies, both in the pollen grain and in the pollen tube, also highlighting the importance of the genes involved in the formation and development of apertures. To the three models previously described by us, a new variant is added for some species of Meconopsis, and the granular infratectum is also considered a derived character and not primitive as previously. The lamellar foot layer is a character present in Euptelea and in most species of the Fumarioideae subfamily. This data is corroborated by cytochemical techniques. Regarding the three models of aperture development already described, we added a new model in Bocconia and Macleaya with endoaperture and two new variants with exine oncus and/or intine oncus. Another feature studied is the tapetum which is of the secretory type and it presents ultrastructural differences between orbicules-producing and non-orbicules-producing species. In relation to the multilamellar bodies found in the cytoplasm near the apertures and at the apex of the growing pollen tube, we have related these structures, which are accumulations of membranes, as a reserve of membranes to be used at times of maximum growth. Finally, we have been able to verify that the INP1 gene involved in the development of apertures is present in basal eudicots (EcINP1). Furthermore, in the samples of inaperturate pollen obtained, it has been found that the apertures do not seem to be essential for the germination of pollen grains in the species studied. We believe that ultrastructural and genetic studies should continue in as many species of the order Ranunculales as possible, which would add value to the characters found in Papaveraceae and would also serve as a model for other groups of angiosperms.