Pollen morphology of Ligeriinae Hanst. (Gesneriaceae): Diagnostic features and their systematic importance

The subtribe Ligeriinae, composed of three genera (Paliavana Vand., Sinningia Ness and Vanhouttea Lem.) and species with wide morphological differentiation, has not been investigated satisfactorily yet in terms of palynology. Thus, the pollen grains of 35 Brazilian species of Ligeriinae (Gesneriaceae) were studied under light microscopy and some species under scanning and transmission electron microscopy. The aim of this study was to characterize the pollen morphology of selected species from the subtribe presenting morphological pollen data (qualitative and quantitative) in an attempt to characterize the studied genera and provide diagnostic data in their systematics. This represents an initial study for this tribe as it involves approximately one third of the species. The pollen grains were acetolyzed, measured and described qualitatively. Quantitative data were analyzed by descriptive statistics and multivariate statistics. The species were analyzed considering 12 quantitative pollen characteristics. The analyses were conducted on a total of 76 specimens sampled. The study revealed that the diagnostic morphological features of the pollen grains studied were: amb, shape, type of apertures and exine ornamentation. On the basis of these traits, Vanhouttea calcarata and all Sinningia species show similarity, while the two Paliavana species differ from each other and are easily discriminated also from the two other genera. Furthermore, the Sinningia species analyzed so far can be characterized as stenopalynous. The pollen characteristics are useful for the taxonomical study of these genera. Nevertheless, the results obtained indicate the need to expand the palynological investigations in the genus Sinningia