Pollen morphology of Gyrostemonaceae,Bataceae andKoeberlinia

Pollen morphology of Gyrostemonaceae, Bataceae, andKoeberlinia, which have been affiliated with glucosinolate-producing taxa, was examined by field emission scanning and transmission electron microscopy. Pollen grains of Gyrostemonaceae are tricolpate with scabrate-spinulate surface and have a thick, unstratified exine, while those of Bataceae are tricolporoidate with granular surface and have a thin exine with a single, outermost granular layer. Gyrostemonaceae and Bataceae, which had often been considered sister taxa based on palynological similarity and now are considered more distantly related, have a similar spongy ektexine, but differences between them are evident.Koeberlinia, which is recently considered a sister group to Bataceae+Salvadoraceae (with no spongy ektexine), has tricolporoidate pollen composed of a plesiomorphic, stratified exine with columellae. The totality of evidence indicates that, contrary to earlier observations, pollen of Gyrostemonaceae and Bataceae does not closely resemble each other, and that the spongy ektexine, which looks to be similar in TEM sections, is a homoplasy that evolved independently in the two families. Dedicated to the late Prof. Emer. Kankichi Sohma (August 28, 1926–June 26, 1995), who supervised us for our M. Sc. and D. Sc. programs at Tohoku University, Sendai. He died after his 40 years career in palynology; his wide range of interests and enthusiasm for research, and his unfailing encouragement for students are greatly missed.