Pollen grain morphology of physaria kingii subsp. kaibabensis and two congeners

Abstract In this study we focus on the pollen morphology of Physaria kingii subsp. kaibabensis and two congeners, Physaria arizonica and P. kingii subsp. latifolia, found on the Kaibab Plateau, Arizona, to differentiate further among these species. We collected plant material from 2 sites/species, with 10 plants/site used to image 10 pollen grains/plant. We described pollen grains (i.e., polar axis [P], equatorial diameter [E], P/E ratio, shape, exine structure, and aperture number) using scanning electron microscopy. All species imaged had pollen grains with reticulate surfaces and were pentacolpate. We found significant differences among species for equatorial diameter and P/E ratio, but not for polar axis. This study provides additional information that can be incorporated in species descriptions.