Light transmittance by apple leaves and canopies.
Light transmittance and reflectance of sun and shade leaves of apple (cv. Golden Delicious) were measured from May to September over the 380-700 nm wavelength range. The mean light absorptance over the range 400-700 nm of both leaf types was >85% except in May when the leaves were immature and bright green. Sun leaves had a greater specific leaf weight and a lower transmittance than shade leaves but reflectance of the 2 types was similar. The proportion of visible to near infra-red radiation decreased beneath hedgerow orchards. Within patches of shade in the visible waveband, the proportion of blue light was increased and that of red decreased.