Development of A Two-Variable Spatial Leaf Photosynthetic Model of Irwin Mango Grown in Greenhouse

To determine the adequate levels of light intensity and CO2 concentration for mango grown in greenhouses, quantitative measurements of photosynthetic rates at various leaf positions in the tree are required. The objective of this study was to develop two-variable leaf photosynthetic models of Irwin mango (Mangifera indica L. cv. Irwin) using light intensity and CO2 concentration at different leaf positions. Leaf photosynthetic rates at different positions (top, middle, and bottom) were measured by a leaf photosynthesis analyzer at light intensities (0, 50, 100, 200, 300, 400, 600, and 800μmol·m-2·s-1) with CO2 concentrations (100, 400, 800, 1200, and 1600μmol·moL-1). The two-variable model consisted of the two leaf photosynthetic models expressed as negative exponential functions for light intensity and CO2 concentrations, respectively. The photosynthetic rates of top leaves were saturated at a light intensity of 400μmol·m-2·s-1, while those of middle and bottom leaves saturated at 200μmol·m-2·s-1. The leaf photosynthetic rates did not reach the saturation point at a CO2 concentration of 1600 ìmolmoL-1. In validation of the model, the estimated photosynthetic rates at top and bottom leaves showed better agreements with the measured ones than the middle leaves. It is expected that the optimal conditions of light intensity and CO2 concentration can be determined for maximizing photosynthetic rates of Irwin mango grown in greenhouses by using the two-variable model.