MODELING PHOTOSYNTHESIS OF HETEROGENEOUS ROSE CROP CANOPIES IN THE GREENHOUSE

A new canopy training system (“bent canopy”) is widely used in greenhouse rose production. The bent canopy consists of a upright hedge and a mat of bent shoots between the hedges. The idea of this heterogeneous canopy is to utilize radiation that falls into the aisle space. A radiative transfer model was developed for a bent canopy. Diffuse and direct light distribution and absorption were simulated by calculating the path length of attenuated light through the canopy. Assimilation rates of sunlit and shaded leaf area were then calculated in relation to position within the canopy and time of day. Numerical integration of the sunlit and shaded assimilation rates over the respective leaf area index (LAI), leaf age, and over the day yielded diurnal course of canopy photosynthesis. The geometry of the canopy was described by hedge height and width, depth and width of the bent canopy, row direction, leaf angle, and leaf area density (LAD). The simulation indicated that bent canopy system is less sensitive to row direction than the conventional hedgerow canopy and that the desired LAD of the bent portion was related to the LAD of the upright hedges