Pollen Morphology ofParapteropyrumand Some Putatively Related Genera (Polygonaceae – Atraphaxideae)

The pollen of the monotypic genus Parapteropyrum and 10 species from three putatively related genera (Pteropyrum, Atraphaxis and Calligonum) in the tribe Atraphaxideae was examined by light and scanming electron microscopy. Three pollen types, differing in exine sculpturing can be recognized: (1) microreticulate in Parapteropyrum and Pteropyrum (2) striato-reticulate to striate in Atraphaxis (3) punctate with perforations in most Calligonum species. Pollen grains of Parapteropyrum and Pteropyrum are morphologically very similar and the only difference between them is in size. Pollen morphology therefore does not support a generic distinction for Parapteropyrum. The distinctive surface pattern of Atraphaxis pollen grains suggests no very close relationship with Parapteropyrum and Pteropyrum nor with those species of Calligonum investigated. From palynological data it seems probable that Atraphaxis evolved independently into a specialized group from the common ancestral stock of the tribe Atraphaxideae.