XVI International Botanical Congess

A scanning electron microscopy and light microscopy survey of pollen morphology in the Rumiceae (49 taxa from 4 genera, Polygonaceae) was undertaken to help elucidate systematic relationships within the tribe. Pollen is small to large, oblate-spheroidal to prolate, mostly tricolporate (rarely 4-9 pantocolporate). The exine is mostly from perforate to microreticulate with very finely and evenly scattered with granular scabrae, except one Himalayan taxon, Rheum nobile (Rheum sect. Deserticolae) that has a striated baculate with many scabrae on the surface. One major evolutionary trend is postulated, i.e., from the 3-colporate with long colpi to short, very reduced colpi. The correlation between exine thickness, pollen sizes and pollination vector, especially in connection with the Wodehouse's hypothesis is also briefly discussed.