Effects of leaf surface wax on leaf spectrum and hyperspectral vegetation indices

Many hyperspectral vegetation indices can be used to estimate the biochemical contents such as pigment content, nondestructively. These reflectance indices are influenced by some leaf surface structure, such as wax, and the existence of the wax affects the performance of the indices on the estimation of the biochemical contents. This research studied the possible effects of the leaf surface wax on the reflectance of the same leaf before and after removal of leaf wax. We found that dewaxing had decreased the reflectance between wavelength 400 and 1000nm, and the decrease depends on the wavelength. The changes of 37 hyperspectral indices before and after the wax removal were compared. The results revealed that some indices such as PSNDb, R672/R550, SIPI and WBI were not affected much by the dewaxing process and are thought relatively robust to estimate the biochemical contents.