Pollen morphology of the genera Irlbachia, Tachia, Voyria and Voyriella (Gentianaceae Juss.) found in the Reserva Florestal Adolpho Ducke (Amazonas, Brazil)

Abstract

A pollen morphology study of the Gentianaceae Juss. of Reserva Florestal Adolpho Ducke (Manaus, Brazil) was performed. The pollen grains of the studied species varied morphologically in their pollen units (tetrads or monads), size (small, medium and large), shape (oblate, suboblate, oblate spheroidal, spheroidal, prolate spheroidal and prolate), polarity (heteropolar, isopolar or subisopolar), symmetry (bilateral or radial) and number and type of aperture (3-colporate and 1-3porate). In relation to ornamentation, pollen grains had a sexine that was psilate in the Voyria species, microreticulate in Voyriella parviflora and reticulate heterobrochate in Tachia grandiflora and Irlbachia alata. The exine in I. alata showed great variability in the size and shape of the lumina, in addition to clavae of various sizes in the mesocolpium and apocolpium areas. In Tachia grandiflora, besides to long colpi, the heterobrochate exine demonstrated an increase in the lumina in the mesocolpium areas that decreased considerably in the apocolpium areas. In the species of Voyria, the pollen grains showed differences in shape, polarity and the number of apertures, which were spherical, isopolar and 3-porate in Voyria spruceana; prolate/oval, heteropolar and 1-porate in Voyria tenella; and oblate/elliptical (reniform), heteropolar and 2(3)-porate in Voyria aphylla and Voyria caerulea. The variations in pollen morphology and the peculiar characteristics of the genus suggest that Voyria should be treated as a unique taxon within Gentianaceae.