Leaf surface characterization of the Tabu-No-Ki tree Machilus thunbergii using electron microscopy and white light scanning interferometry

Leaf surface features were investigated in the Tabu-No-Ki tree Machilus thunbergii by electron microscopy and white light scanning interferometry. Mature leaves of the tree were air-dried at room temperature and sputter-coated with platinum. The most prominent epicuticular wax structures of M. thunbergii leaves included granules, angular rodlets and transversely ridged rodlets. Wax granules were often observed on the adaxial leaf surface. Meanwhile, the abaxial leaf surface was characterized by transversely ridged rodlets in which the ridges were perpendicular to their longitudinal axis. Having several facets, the angular rodlets were straight and grew among clusters of transversely ridged rodlets. The adaxial leaf surface of M. thunbergii appeared to be smooth and less undulating than the abaxial leaf surface. Clusters of epicuticular waxes were predominant on the abaxial leaf surface. The average heights of the adaxial and abaxial leaf surfaces were 1.79 ± 0.58 and 3.65 ± 0.93 μm, respectively. The average roughness and root-mean-square roughness values were lower those on the adaxial surface than on the abaxial surface. These results suggest that the transversely ridged rodlets significantly contribute to the increased surface roughness on the abaxial leaf surface.