A taxonomic aid arising from pollen grains of Cestrum L. and Solanum L. (Solanaceae): differences in ornamentation and aperture

Abstract

Solanaceae is represented by herbs, shrubs, trees and climbing plants and has cosmopolitan distribution, with a large number of native species in the Neotropical region. This study aimed to characterize the pollen morphology of ten species of Solanaceae (especially species of Cestrum and Solanum) from Cerrado forest fragments in Brazil, in order to contribute to the palynology, taxonomy and conservation of degraded areas. Pollen grains were acetolysed, measured and photographed using light and scanning electron microscopy. Qualitative data were described, and quantitative data were analyzed statistically according to sample size. Morphologically, the studied pollen grains vary in size (small to medium), amb (subcircular to subtriangular), shape (oblate spheroidal to subprolate), aperture details (very long, long or narrow colpi, rounded or tapered at the polar ends, colpi with margo, sometimes with a fastigium, endoapertures can present costa and median constriction) and ornamentation (psilate, rugulate, striate or microreticulate). We observed rugulate or striate pollen grains without fastigium for Cestrum species, whereas psilate or microreticulate pollen grains with fastigium were observed for Solanum species. Qualitative data on diameters and aperture measurements were also found to be important in characterizing the two genera. The results obtained here confirm Solanaceae as an eurypalynous family.