Photosynthesis models and canopy management optimization in cut-flower roses

A model for photosynthesis is an essential unit within a crop simulation model upon which other modules should be built and linked. In this work, the Farquhar photosynthesis model was combined with a Ball-Berry type stomatal conductance model and an energy balance model. The resulting coupled model of leaf photosynthesis, stomatal conductance, and transpiration was calibrated and tested for rose leaves (Rosa hybrida L. cv. Kardinal). Model prediction of net photosynthesis agreed reasonably well with the measured data. The model tended to underestimate stomatal conductance and transpiration. The model could be useful for growers to make cultural decisions in the greenhouse.; Whole-plant photosynthesis was measured with an open chamber system. The system was used to monitor diurnal patterns of whole-plant gas exchange in response to environmental variables. A model for leaf photosynthesis was calibrated and scaled up to the whole-plant level. Simulated whole-plant photosynthesis compared well with the observed data.; Productivity, quality and economic feasibility of a new rose crop canopy management regime using shoot-bending were evaluated. Cut-flower production of ‘Kardinal’ and ‘Fire N Ice’ rose cultivars was compared with two canopy management regimes: (shoot-bending vs. non-bending), and two different root media (Coconut Coir vs. UC Mix). While shoot-bending resulted in increased stem-length and dry matter of flowering shoots, it also resulted in significantly fewer harvestable flowering shoots. Comparisons of flower production and stem-length between two root media were not as conclusive. Market value of the harvested shoots was modeled to assess the economic feasibility of the two canopy regimes. Shoot-bending was found to be an economically feasible method only when both short-stem roses were discounted and long-stem roses were rewarded with an extra bonus in the market.; Shoot-bending leads to a canopy that consists of upright hedges and a mat of bent shoots (“bent canopy”). Whole crop photosynthesis of the bent canopy roses was compared with the conventional hedgerow canopy using simulation. A radiative transfer model was developed for the bent canopy. Photosynthesis was then calculated in relation to the position within the canopy and time of day. The simulation indicated that the bent canopy is less sensitive to row direction than the hedgerow canopy, and that the optimal leaf area density (LAD) of the bent portion of the canopy was dependent on LAD of upright hedges.