Pollen morphology of some Brazilian species of Hirtella L. (Chrysobalanaceae)

Hirtella (Chrysobalanaceae) comprises about 107 species and less than 10% of its diversity has been sampled in palynological studies, which have only used light microscopy. To better understand the pollen morphology of the genus, pollen grains of fourteen species were examined: H. angustifolia Schott ex Spreng., H. bahienis Prance, H. bicornis Mart. & Zucc., H. ciliata Mart. & Zucc., H. corymbosa Cham. & Schltdl., H. glandulosa Spreng., H. gracilipes (Hook.f.) Prance, H. insignis Briq. ex Prance, H. martiana Hook.f., H. prancei Asprino & Amorim, H. racemosa Lam., H. santosii Prance, H. sprucei Benth. ex Hook.f., and H. triandra Sw. All of the species occur in the state of Bahia, Brazil, and belong to Hirtella sect. Hirtella. The pollen of Hirtella duckei Huber, an Amazonian species that belongs to Hirtella sect. Myrmecophila, was also analyzed for comparison. The pollen grains were acetolyzed, measured, described, and photomicrographed using light microscopy, and subsamples of acetolyzed material were also analyzed using scanning electron microscopy. The pollen of the studied species presented features similar to those previously reported for Hirtella, such as size, shape, number of apertures, and general features of the exine. Based on the SEM analysis, three ornamentation patterns of the exine (microreticulate-rugulate, rugulate-perforate, and psilate-perforate) are reported for the first time for the genus. Little could be inferred about the taxonomy of Hirtella based on the pollen morphology, and there were no pollen characters for H. duckei that corroborate or refute its separation in a different section from the other species studied. Nevertheless, the present study provides new data about Hirtella that contribute to what is known about the pollen morphology of the genus.