Pollen morphology of the Ipomoea (Convolvulaceae) in Taiwan

Pollen of 18 species of Ipomoea in Taiwan was examined in LM and SEM. Light microscope study of pollen morphology has shown that all examined species share common pollen morphological characters - spherical shape, pantoporate apertures, and tectum with spinulate processes. On the basis of exine stratification, two different groups of this genus were defined: The Group 1 pollen include I. acuminata and 9 other species, possess spines, extraporal regions and tetragonal to hexagonal areas. The pores are surrounded by an extraporal region, and the spines and the ridges of the bacula form a tetragonal to hexagonal area around each extraporal region. Each pore is covered with an operculum which is peeled off after acetolysis. Fine reticula are present all over the surface of the grain. The reticula consist of very minute lumina. The Group 2 pollen include I. obscura and 7 other species. The extraporal regions and tetragonal to hexagonal areas are absent. Minute lumina are also present all over the surface of the grain. A key for distinguishing Taiwan's various species of Ipomoea, based on exine stratification and spinal characteristics, was made.