Pollen morphology of selected species of the subfamily Bombacoideae (Malvaceae sensu lato)

We analyzed the pollen grains of 11 species within the subfamily Bombacoideae. The pollen grains were acetolyzed, after which they were analyzed and photographed under light microscopy. Unacetolyzed pollen grains were analyzed and photomicrographed under scanning electron microscopy. We studied pollen characters such as shape, size, exine ornamentation and aperture type. The species were separated by a pollen key, which considers the presence or absence of calotte in the pollen grains. This attribute separated Ceiba and Eriotheca from the other genera. Some species are differentiated by specific characters: in Bombacopsis glabra and B. stenopetala, the sexine is rugulate or vermiculate with isolated pilate elements; in B. calophylla, the pollen grains are sinu-aperturate; Ceiba speciosa show atypical, duplicolumellate sexine; C. erianthos is the only species with 5-colporate pollen grains and a pentagonal amb; in Pachira aquatica the reticulum has muri with spiculaspinulose muri (reticulum cristate). The variation in the pollen morphology confirms the eurypalynous status of the genera studied here.