The pollen of Takhtajania perrieri (Winteraceae)

Pollen morphology and ultrastructure of Takhtajania perrieri (Capuron) Baranova & J.-F. Leroy, the Malagasy member of the Winteraceae, were studied and compared with pollen of other members of this primitive angiosperm family. Pollen is in permanent tetrahedral tetrads, which are the largest in the family. As in Drimys and Pseudowintera, the apertures are expanded into protuberant papillae, suggesting premature commencement of growth of the pollen tubes. Apertures are circular or slightly oval, and it is concluded that previous reports of colpate and trichotomocolpate (trichotomosulcate) apertures, based on the study of dried material from the type specimen, are incorrect. The exine is reticulate and tectate-columellate and most columellae have characteristic expanded bases where they join the foot layer. Beneath the foot layer is an endexine and an intine, which is two-layered in apertural areas, as in other Winteraceae. As in some other genera, the aperture is surrounded by an annulus, with an underlying thickened endexine consisting of tangentially aligned lamellae. The septal exine is highly reduced, and small gaps in the ectexine are plugged with endexine, suggesting that pollen mitosis is asynchronous within a tetrad, as in Pseudowintera and Drimys, but in contrast to Belliolum, Bubbia, Exospermum, Tasmannia, and Zygogynum, in which these gaps remain or are blocked by the deposition of intine after pollen mitosis. On the basis of its pollen morphology, Takhtajania seems most closely related to Drimys and Pseudowintera.