Modeling of Whole Canopy Photosynthesis of Romaine Lettuce Using Controlled Growth Chamber

Abstract

The objective of this study was to develop a canopy photosynthesis model of Romaine lettuce that can be applied to plant factories using three parameters of CO2 concentration, light intensity and growth stage. The plants were grown in plant factory modules and photosynthesis rates were measured in sealed growth chambers made of acrylic. First of all, in combining CO2 concentration and light intensity conditions, it was analyzed whether it is efficient to fix a certain factor and control (change) the other one. The time constant when controlling the CO2 concentrations with a fixed light intensity was 3.2 times higher and the deviation was larger than when changing the light intensity. Based on these results, canopy photosynthetic rates of the plants were measured at five CO2 concentrations (600 to 2200 μmol • mol-1), 5 light conditions (60 to 340 μmol • m-2 • s-1), and four growth stages (5, 10, 15 and 20 days after transplanting). The parameterization and regression analysis were used to develop the canopy photosynthesis model according to the growth stage. The canopy photosynthetic rates estimated using the developed model showed good agreement with the measured ones (R2 = 0.87). It is expected that the developed model will help to determine the optimum CO2 concentration and light intensity conditions with growth stage required for the efficient production in plant factories.