Pollen morphology and ultrastructure of Saururaceae

Abstract

The fine details of pollen grains in Saururaceae have, until now, been relatively obscure and incomplete. The recent discovery of fossil saururaceous pollen led us to examine the six extant and one fossil species of Saururaceae for details of pollen morphology and ultrastructure. Pollen grains of Saururaceae are characterized as small to minute, boat-shaped-elliptic to globose, monosulcate with granulate sculpturing of the aperture membrane, with a punctate tectum. Pollen grains of Houttuynia are the largest. While pollen grains of Anemopsis, Houttuynia, and Saururus have papillae bordering the puncta, those of Gymnotheca are distinctive in lacking such papillae. Similarly, all genera have a smooth tectum, except for Gymnotheca, which has microstriate tectal sculpturing. Pollen grains of Gymnotheca and the fossil have a well-defined columellar infratectum, while in modern Saururus, Anemopsis and Houttuynia the columellae are irregular in section. Endexine is clearly present in all taxa. This study is the first to characterize pollen from all the species in Saururaceae, using both scanning and transmission electron microscopy. Such knowledge will help recognize fossil pollen of Saururaceae, a family with a poor palynological record. © 2007 Taylor & Francis.