2017 ASHS Annual Conference

Photosynthesis is an important physiological response in determination of CO₂ fertilization in greenhouse and further estimation of crop growth. In order to estimate the whole plant photosynthetic rate, it is necessary to investigate the light interception of the crops changing with environmental and morphological factors. The objective of this study were to analyze the light interception of the plant using a 3D plant model and ray-tracing, determine the spatial distribution of photosynthetic rate, calculate the whole plant photosynthetic rate of mango (Mangifera indica L.) grown in greenhouses. In case of mango, it is difficult to measure the actual light interception at canopy level due to its vase shape. Two-year-old Irwin mango plants were used. The light interception and whole plant photosynthetic rate was measured at artificial and natural lights using a closed chamber. A 3D plant model was constructed and the ray-tracing simulation was conducted for calculating the photosynthetic rate with two-variable leaf photosynthetic rate model of mango. At artificial light, the calculated photosynthetic rate increased from 1.7 to 3.1 μmol∙m^-2∙s^-1 with increasing CO₂ concentration. At natural light, the photosynthetic rate increased from 0.2 μmol∙m^-2∙s^-1 at 06:00 and reached the maximum of 3.7 μmol∙m^-2∙s^-1 at 09:00, then gradually decreased to -0.5 μmol∙m^-2∙s^-1 at 18:00. In validation, simulation results showed good agreements with measured ones with R² = 0.633 and RMSE = 0.615. From the results, it was supposed that this method could accurately estimate the whole plant photosynthetic rate and be useful for adequate CO₂ fertilization.