Taxonomic significance of pollen morphology in the tribe Helieae (Gentianaceae) from the Atlantic Forest, Brazil

The Atlantic Forest possesses great biodiversity with numerous endemic species. This, along with fragmentation and loss of natural environments resulting from anthropic actions, place this complex ecosystem among global biodiversity hotspots. The objective of this study was to contribute the palynological knowledge of 17 species of six genera subordinate to the Helieae tribe using light and scanning electron microscopy (SEM). Acetolysed pollen material was used for making measurements and descriptions under light microscopy, while non-acetolysed pollen grains were used for obtaining SEM images. Pollen grains were found as monads in Macrocarpaea, rhomboidal tetrads in Calolisianthus amplissimus and tetrahedral tetrads in the other species. The type of aperture varied among colporate, hemicolporate, porate and hemiporate, while the ornamentation of the sexine varied among genera including reticulate, gemmate-pilate, rugulate, gemmate-baculate and rugulate-echinate. Using the results, a key and multivariate analysis were developed that confirm the separation of the species in the tribe. The present study provides a broad base of information for the taxonomy of the group, as well as serving other areas such as aeropalynology, melissopalynology and paleopalynology.