Three-Dimensional Radiation Transfer Modelling in a Dicotyledon Leaf.

The propagation of light in a typical dicotylon leaf is investigated with a new Monte Carlo ray tracing model. The three-dimensional internal cellular structure of the various leaf tissues, including the epidermis, the palisade parenchyma and the spongy mesophyll, is explicitly described. Cells of different tissue are assigned appropriate morphologies and contain realistic amounts of water and chlorophyll. Each cell constituent is characterized by an index of refraction and an absorption coefficient. The objective of this work is to investigate how the internal three-dimensional structure of the tissues and the optical properties of cell constituents control the reflectance and transmittance of the leaf. Model results compare favorably with laboratory observations. The influence of the roughness of the epidermis on the reflection and absorption of light is investigated, and simulation results confirm that convex cells in the epoidermis focus light on the palisade parenchyma and increase the absorption of radiation.JRC.(SAI)-Space Application Institut