Dr. Jeffrey M. Osborn

Publication Abstract

Osborn, J. M. 2000. Pollen morphology and ultrastructure of gymnospermous anthophytes. In: M. M. Harley, C. M. Morton, and S. Blackmore (Editors), Pollen and Spores: Morphology and Biology, pages 163-185. Royal Botanic Gardens, Kew, UK.

In recent years, phylogenetic analyses of seed plants have suggested a close relationship among angiosperms and three orders of gymnosperms, including Gnetales, Bennettitales, and Pentoxylales. On the basis of several vegetative and reproductive features, these studies have linked the three gymnosperm groups along with angiosperms into a single ‘anthophyte’ clade. Furthermore, reports of Cretaceous fossils with in situ Eucommiidites-type pollen indicate that plants that produced these types of pollen grains (Erdtmanithecales) may also have their affinities nested within the same clade of highly derived seed plants. Two unifying palynological characters are shared among all anthophyte groups; these include a non-saccate condition and a granular sexine infrastructure. In the present paper, pollen morphology and ultrastructure are reviewed for the extant and fossil genera of the four anthophyte orders of gymnosperms that have been studied with transmission electron microscopy. The taxa reviewed include Gnetales (Ephedra, Welwitschia, Gnetum, Ephedripites, Equisetosporites), Bennettitales (Leguminanthus, Cycadeoidea, Monosulcites), Pentoxylales (Sahnia), and Erdtmanithecales (Eucommiidites, Erdtmanitheca, Eucommiitheca). Pollen of these taxa is compared with regard to size, shape, aperture type and location, surface ornamentation, and exine infrastructure. These characters are also discussed regarding their systematic and phylogenetic significance.

Anthophyte, Bennettitales, Erdtmanithecales, Eucommiidites, Gnetales, Gymnosperm, Pentoxylales, Pollen, Ultrastructure.