Endemic Papilionoideae of the Caatinga: a contribution to the palynological knowledge of Leguminosae

ABSTRACT Papilionoideae is the most diverse subfamily of Leguminosae, representing approximately 39 % of its species. Although it is particularly species rich and diverse in the Caatinga, the main phytophysiognomy of the semiarid Northeast Region of Brazil, little is known about the pollen morphology of the species that occur there. This study analyzes and describes the pollen morphology of the 27 species of Papilionoideae endemic to the Caatinga. Pollen grains were acetolyzed, mounted on permanent slides, measured, described and photomicrographed using light and scanning electron microscopy (LM and SEM, respectively). The main variable morphological features were pollen grain size, shape, amb, apertural type and exine ornamentation under LM (microreticulate, reticulate, psilate or finely scabrate) and SEM (microreticulate, reticulate, rugulate, granulate, fossulate and perforate). High intergeneric morphological heterogeneity was observed while morphological variation within each genus was subtle. Nonetheless, size, endoaperture shape, fastigium presence/absence and exine ornamentation were found to be important characteristics for the identification of some species.