Evidence of pseudomonad pollen formation in Hypolytrum (Mapanioideae, Cyperaceae)

Cyperaceae are characterised by typical simultaneous microsporogenesis that results in the formation of pseudomonad pollen. Morphological studies indicate the occurrence of a distinct pollen type in Mapanioideae, the spherical and monoporate Mapania-type pollen, found in representatives of Hypolytreae. This study investigates anther and pollen development in species of Hypolytrum for a better understanding of the mapanioid pollen type. Stages in microsporogenesis and microgametogenesis were analysed in both Hypolytrum (Mapanioideae, Hypolytreae; five species sampled) and Rhynchospora (Cyperoideae; two species studied). The latter was used as a comparator, known for the occurrence of pseudomonads. The results presented here confirm those already reported for the family, regardless of genus. The most important differences are morphological, not developmental. All species sampled of both genera had Cyperaceae-type simultaneous microsporogenesis resulting in pseudomonad pollen. Predictions that Mapania-type pollen in Hypolytrum would be monad are refuted. Anthers examined of Rhynchospora showed phenolic idioblasts, while those of species of Hypolytrum did not. There is need for ontogenetic studies on the other genera of Hypolytreae, such as Mapania and Scirpodendron, to extend and test the generality of our observations across the Hypolytreae.