A comparative study of the pollen morphology of Prototulbaghia Vosa and other genera in the Alliaceae

摘要

The southern African Alliaceae Borkh. is represented by four genera (Allium L., Nothoscordum Kunth, Tulbaghia L. and Prototulbaghia Vosa) and 28 species. Prototulbaghia is a monotypic genus endemic to the Leolo Mountains that are situated in the Sekhukhuneland Centre of Endemism. The pollen morphology of this genus has not been documented before, and the aim is thus to describe the pollen morphology of Prototulbaghia siebertii Vosa and to compare it with the pollen of Nothoscordum borbonicum Kunth, Tulbaghia simmleri P. Beauv. en T. violaceae Harv. Floral material of the four species was collected from the gardens of the North-West University (NWU) campus and a special collection held at the NWU-botanical garden. Pollen was examined with scanning electron- and light microscopy. The pollen morphology of the four species is perprolate and monosulcate, and the surface sculpturing is reticulate and heterobrochate. The pollen of Prototulbaghia siebertii however, displays a unique characteristic as the grains fold breadth-wise causing the tips to touch. Hence, the grain displays a triangular shape and has a disulcate appearance. Two hypotheses can be formulated to explain this phenomenon. The folding can either be due to the process of harmomegathy or a still unknown event that occurs during the development of the pollen grain. These processes will be investigated further to determine the mechanism of the folding, whether it is a unique taxonomic character for the genus, and whether it is of evolutionary significance within the Alliaceae.