Simulating light quantity and quality over plant organs using a ray-tracing method to investigate plant responses in growth chambers

Abstract

Ray-tracing models enable the assessment of light quantity and quality intercepted by plant organs, supporting biological studies in growth chambers with varying light conditions. However, their validation within canopies and clear usage methods remain limited. This work establishes a reliable method for using these models. The method includes i) accounting for the intensity and spectrum of light sources in the calibration procedure; ii) a generic calibration strategy using a few well-placed light measurement points based on chamber geometry. It evaluates the method to simulate light phylloclimate at the organ scale across biologically relevant wavebands of contrasted widths and properties. Using the SEC2 light simulation framework, three virtual experiments were conducted in a growth chamber, with and without rose plants. Inputs included chamber geometry, material optical properties, lamp emissions, and digitised plant mock-ups. Simulations were compared with spectral measurements at various chamber positions and sensor orientations, both without plants and inside a canopy. Results showed high accuracy in replicating spatial light variability, with RMSE ranging 0.011 to 0.021 and 0.014–0.038 μmol m-2s-1nm-1 across different wavebands and sensor orientations, for vertical and horizontal transects, respectively. Applying this approach to a case study demonstrated its effectiveness in formulating new biological hypotheses regarding the role of local light in regulating bud outgrowth. This was achieved by highlighting differences in phylloclimate induced by variations in plant architecture. This work thus provides a comprehensive framework for facilitating the application of ray-tracing models in growth chamber studies