Background and Aims The objective of this study is to examine the palynological diversity of Balsaminaceae (two genera/61000 species), Tetrameristaceae (two genera/two species) and Pellicieraceae (one genus/one species). The diversity found will be used to infer the systematic value of pollen features within the balsaminoid clade. Methods Pollen morphology and ultrastructure of 29 species, representing all families of the balsaminoid clade except Marcgraviaceae, are investigated by means of light microscopy, scanning electron microscopy and transmission electron microscopy. Key Results Balsaminaceae pollen is small to medium sized with three to four apertures, which can be either colpate or porate, and a sexine sculpturing varying from coarsely reticulate to almost microreticulate. Tetrameristaceae pollen is small sized, 3-colporate, with a heterobrochate reticulate sculpturing and granules present in the lumina. Pellicieraceae pollen is large sized, 3-colporate with long ectocolpi and a perforate sexine sculpturing with large verrucae. Furthermore, Pelliciera is characterized by the occurrence of aggregated orbicules, while orbicules are completely absent in both Balsaminaceae and Tetrameristaceae. Balsaminaceae pollen differs from the other balsaminoid families due to the occurrence of colpate or porate grains with an oblate to peroblate shape, a very thin foot layer and a lamellated endexine. Conclusions From a pollen morphological point of view, Balsaminaceae are completely different from the other balsaminoid families. Therefore, no pollen morphological synapomorphies could be defined for the balsaminoid clade. However, various pollen features were observed that could indicate a possible relationship between Tetrameristaceae, Pellicieraceae and Marcgraviaceae. Despite the palynological similarities in the latter three families, it remains unclear to what extent they are related to each other.

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Annals of Botany
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Janssens, S. B., Lens, F., Dressler, S., Geuten, K., Smets, E., & Vinckier, S. (2005). Palynological Variation in Balsaminoid Ericales. II. Balsaminaceae, Tetrameristaceae, Pellicieraceae and General Conclusions. Annals of Botany, 96(6), 1061–1073.