Simulating the Distribution of R/FR in Maize Canopies with Monte Carlo Ray Tracing Approach

R/FR (red to far-red ratio) is a key light signal for plants to detect the oncoming competition and initiate the shade avoidance syndrome. This study is aim to simulate the R/FR signal received by maize plants based on a 3D canopy radiative model. Optical properties of maize leaf were characterized by an adapted Cook-Torrance model for reflectance and a Lambert model for transmittance. Virtual maize canopies were reconstructed with triangle facets by digitizing the 3D architecture of maize plants in the field. The distributions of red and far-red light within canopies were simulated by Monte Carlo ray tracing methods. R/FR received by triangle facets of canopies was calculated from these red and far-red light distributions. Finally, the distributions of R/FR within two maize canopies at two growth stages were simulated under three solar angles. Low R/FR in the canopy of maize at filling stage indicated potential competition of neighboring plants. Solar angles change the distribution of R/FR within canopy. It is recommended to be examined on the whole day time course that covering a large range of solar angles.