Notes on the genus Amorphophallus (Araceae) - 8 Pollen morphology of Amorphophallus and Pseudodracontium

The pollen of Amorphophallus and Pseudodracontium has been studied with light microscopy and scanning and transmission electron microscopy. Amorphophallus pollen is always inaperturate, has a wide size range, and shows highly diverse exine surfaces. Eight main surface types have been distinguished, most of which are not clear-cut and show considerable infratypic variation. The exine is unusual and consists of a distinct, acetolysis-resistant endexine and a usually nonresistant ectexine. The latter is ultrastructurally diverse by the presence/absence of variously sized, shaped, and distributed dark granules of unknown composition. Comparison with a preliminary subdivision based on macromorphological data indicates that the pollen surface type often supports infrageneric groupings. However, groups considered to be monophyletic sometimes have highly diverse pollen grains. The genus Pseudodracontium, although macromorphologically very near to Amorphophallus, has a clearly distinct pollen surface type. (C) 1998 Elsevier Science B.V. All rights reserved.