Analysis of Canopy Photosynthesis Using 3D Paprika Model and Ray-Tracing Simulation

Abstract

Canopy photosynthesis has typically been estimated using mathematical models that have the following assumptions: the light interception inside the canopy exponentially decays in a vertical distribution, and the photosynthetic capacity is proportional to the light interception as a result of acclimation. However, in actual situations, light interception in the canopy is quite different depending on several environmental factors such as the location, microclimate, leaf area index, and canopy architecture, and it is important to apply these variances in an analysis. The objectives of the current study are to estimate the canopy photosynthesis of paprika (Capsicum annuum L.) with an analysis of the intercepted irradiation of the canopy using a 3D ray-tracing simulation and by applying a photosynthetic capacity in each layer. By inputting the structural data of an actual plant, the 3D architecture of paprika could be developed using graphic software. With a 3D virtual plant, simulations were conducted using ray-tracing software. Depending on the sunlight properties, the vertical distributions of intercepted irradiance within the plant were dynamically altered, and their patterns were also changed according to the time of day. The light curve and A/Ci curve of each layer were measured, and the parameters of the photosynthetic capacity used in the Farquhar, von Caemmerer and Berry (FvCB) model were determined at each layer. The photosynthetic capacity within the plant was significantly different among the vertical positions. With the intercepted irradiation data and photosynthetic parameters of each layer, the values of an entire plants photosynthesis rate were estimated by integrating the calculated photosynthetic rate at each layer. The estimated photosynthesis rate of an entire plant showed good agreement with the measured plant using a closed chamber for validation. By expanding this approach to canopy conditions, it is possible to analyse the canopys photosynthesis as a key factor in a cultivation system.