An Assessment of Pollen Morphology in the Genus Vitex L. (Labiatae)

Abstract

Pollen grains of Vitex (Labiatae) a large pantropical genus with a few temperate species, are examined by light microscopy, SEM and TEM. All grains are elliptic and tricolpate. However, exine surface sculpture varies between taxa. Two main morphological groups are recognized: the first is tectate simple-perforate to tectate perforate-fenestrate (with perforations anastomosing); the second tectate micro-reticulate/rugulate with micro-perforations in valleys between muri (the latter form is found in Madagascar taxa which have a long corolla tube). Pollen of the commonly cultivated Vitex negundo is unusual in having supra-rugulate, often collapsed grains. Polar and equatorial sizes are included and the possible taxonomic significance of the morphological differences discussed.