Abstract
Samples of dorsal leaf surfaces taken from 16 species of the subgenus Rhododendron section Tsutsusi were examined to establish distinctive characters indicative of the presence of Ryukyu azalea genes in Kurume azalea hybrids family. The Suzuki Universal Micro-Printing method was used to prepare microscope slides for examination with a light microscope, equipped with differential interference contrast optics. Specific characteristics of the epidermal cells, cuticular topography, and stomata and the existence of trichomes were studied. Recording specific morphological characteristics is an accepted technique for taxonomically differentiating species within section Tsutsusi. Eight groups of the 16 species could be characterized by dorsal leaf features alone. Because the frequencies and sizes of stomata overlapped among species, they were useless as identifying taxonomic characters. Based on our data, R. macrosepalum and R. mucronatum var. ripense which are original species of Ryukyu azalea, are clearly distinguishable from R. kaempferi, R. kiusianum and R. kiusianum var. staense, which are generally considered to be the original species of Kurume azalea hybrids family.
