Abstract

The family Passifloraceae sensu stricto occurs mainly in the Neotropical region. Four genera are represented in the American flora, Ancistrothyrsus Harms, Dilkea Mast. (restricted to the Amazon rainforest), Mitostemma Mast., and Passiflora L. The largest and most studied genus is Passiflora. The three other genera are considerably smaller; Ancistrothyrsus contains two species, Dilkea twelve, and Mitostemma three. This study aimed to perform a palynological characterization of six species belonging to the genera Ancistrothyrsus, Dilkea, and Mitostemma: Ancistrothyrsus tessmannii Harms, Dilkea johannesii Barb. Rodr., Dilkea retusa Mast., Mitostemma brevifilis Gontsch., Mitostemma glaziovii Mast., and Mitostemma jenmanii Mast. Pollen specimens were acetolyzed, measured, described, and photographed with light and scanning electron microscopes. Pollen grains are medium- or large-sized, prolate-spheroidal, 3-colporate in Ancistrothyrsus and Mitostemma and (3)4(5)-colporate in Dilkea. The sexine is thick, reticulate, muri sinuous or straight, simplicolumellate, with two nexine layers in some species. Pollen morphology is an important source of taxonomic information that allows distinguishing and identifying species of the genera Ancistrothyrsus, Dilkea, and Mitostemma, making it possible to draw comparisons with the genus Passiflora. The descriptions presented in this study contributes to the knowledge of the pollen flora of Passifloraceae.

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