Polarization of Light by Vegetation

Here we shall examine the phenomenon of surface-scattered light from both leaves and plant canopies. Results from measurements will show that this surface-scattered light — a quasi-specular reflection if the leaves appear shiny — originates at the interface between the air and the cuticle wax layer. Unlike light that is diffusely reflected by the interior of a leaf, the surface-scattered light never enters the leaf; it is reflected from the first surface encountered. This light is partially polarized and may be described by the Stokes vector. The results show that remotely sensed polarization measurements of a plant canopy contain information about leaf surfaces — information that is independent of the information in the light absorbed or scattered from the leaf mesophyll. The polarized, surface-scattered light does not penetrate the leaf to be absorbed by the metabolic constituents of cells, e.g., cell pigments, or to be multiply scattered at the dielectric boundaries in leaf tissue, e.g., the cell wall and water interfaces.