Effects of pubescence and waxes on the reflectance of leaves in the ultraviolet and photosynthetic wavebands: A comparison of a range of species

Abstract

Total reflectance of ultraviolet and photosynthetically effective wavelengths was measured for a range of different leaf types. Two approaches were employed. Firstly, reflectance of monochromatic wavebands at 330 and 680 nm was measured for a total of 45 different species covering a wide range of genera. In the second, specific leaf types that displayed different degrees of reflectance were treated to remove hairs and waxes that contributed to their reflectance. Selected waxy and non-waxy leaves were also studied in more detail over the spectral range 270-500 nm. It was found that both pubescence (presence of hairs) and glaucousness (presence of a thick epicuticular wax layer) had marked effects on total reflectance. Pubescent leayes tended to be more effective in reflecting longer wavelengths than ultraviolet radiation. The extent of this effect depended on hair type. Glaucous leaves demonstrated that surface waxes were very effective reflectors of both UV and longer wavelength radiation.