Time Change in Spatial Distributions of Light Interception and Photosynthetic Rate of Paprika Estimated by Ray-tracing Simulation

To estimate daily canopy photosynthesis, accurate estimation of canopy light interception according to a daily solar position is needed.However, this process needs a lot of cost, time, manpower, and difficulty when measuring manually.Various modeling approaches have been applied so far, but it was difficult to accurately estimate light interception by conventional methods.The objective of this study is to estimate the spatial distributions of light interception and photosynthetic rate of paprika with time by using 3D-scanned plant models and optical simulation.Structural models of greenhouse paprika were constructed with a portable 3D scanner.To investigate the change in canopy light interception by surrounding plants, the 3D paprika models were arranged at 1×1 and 9×9 isotropic forms with a distance of 60 cm between plants.The light interception was obtained by optical simulation, and the photosynthetic rate was calculated by a rectangular hyperbola model.The spatial distributions of canopy light interception of the 3D paprika model showed different patterns with solar altitude at 9:00, 12:00, and 15:00.The total canopy light interception decreased with an increase of surrounding plants like an arrangement of 9×9, and the decreasing rate was lowest at 12:00.The canopy photosynthetic rate showed a similar tendency with the canopy light interception, but its decreasing rate was lower than that of the light interception due to the saturation of photosynthetic rate of upper leaves of the plants.In this study, by using the 3D-scanned plant model and optical simulation, it was possible to analyze the light interception and photosynthesis of plant canopy under various conditions, and it can be an effective way to estimate accurate light interception and photosynthesis of plants.