Pollen morphology of the monotypic genus Poellnitzia (Alooideae: Asphodelaceae)

Abstract

Poellnitzia Uitewaal (subfamily Alooideae, family Asphodelaceae) has a history of taxonomic confusion and doubtful generic delimitation. It has previously been variously combined with, and separated from, four other genera of the Alooideae. In this study, the taxonomic significance of its pollen morphology was assessed by means of scanning electron microscopy. Plants collected from two populations in the Robertson area, where Poellnitzia is endemic, were included in the survey. Poellnitzia is homogeneous in its pollen morphology; grains are shed as monads, are bilaterally symmetrical, medium in size and have a perforated tectum. The mean pollen size of Poellnitzia (36.4 μm) is greater than that of Chortolirion and Haworthia. However, no marked differences in pollen symmetry, shape, aperture features and fine structure between Poellnitzia and other genera of the Alooideae could be detected. This is in striking contrast to the strong macromorphological evidence for separating Poellnitzia from the other Alooideae genera. The similarity in pollen morphology merely supports the inclusion of Poellnitzia within the subfamily.