An overview of pollen morphology and its systematic significance in the subfamily Arbutoideae of the Ericaceae

stenopalynous

日本花粉学会

日本花粉学会会誌

Subfamily Arbutoideae (Ericaceae) comprises four genera (Arbutus, Arctostaphylos, Comarostaphylos and Ornithostaphylos) and 81 species. We have examined the pollen morphology of 17 species from three of these genera: Arbutus, Arctostaphylos, Comarostaphylos representing using light microscopy (LM) and scanning electron microscopy (SEM) and also, for selected species, transmission electron microscopy (TEM). The Arbutoideae are generally stenopalynous; the four 3-colpor(-oid)ate grains are united in compact rounded permanent tetrads. No pollen morphological characters or character combinations distinguish Arbutoideae within the Ericaceae. However, within the subfamily, Arctostaphylos and Comarostaphylos commonly have smaller pollen tetrads with a thin perforated septum, while Arbutus pollen tetrads are usually larger and characterized by thicker septum without distinct perforations. The rugulate apocolpial exine sculpture of Arctostaphylos is usually less distinct than the coarser rugulate ectexine often observed for the pollen of Arbutus and Comarostaphylos.