Dynamic analysis of water and nutrient uptake for New Guinea impatiens

big leaf combination model was modified to predict the transpiration rate of a "low light" crop, New Guinea impatiens 'Equinox', under a greenhouse environment with inputs of solar radiation, air temperature, relative humidity, and air velocity. Canopy area index (CAI) was introduced to account for intercepted solar radiation by small, growing plants. Average stomatal resistance of the plant canopy was estimated using a multiple layer diffusion model. The Michaelis-Menten equation was adapted to estimate the uptake of individual nutrients, such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) based on the microclimate parameters and plant characteristics.;The transpiration and nutrition models were validated experimentally by growing the impatiens on a 100% rockwool soilless medium in a computer controlled greenhouse. A highly accurate lysimeter was effective in measuring the dynamic evapotranspiration (ET) of the canopy. The nutrient solution samples were collected every three hours from a constant volume recirculation system.;A sensitivity analysis indicated that the solar radiation and water vapor pressure deficit of the air were dominant factors affecting the ET. The leaf area index (LAI) increased uniformly after the fourth week of transplant while the CAI developed rapidly after the fourth week of transplant and then slowed down to unity. High radiation periods resulted in high leaf temperatures and maximum transpiration rate of 220 g.Hr;The nutrient model parameters suggested that the nitrogen uptake increased with photosynthetically active radiation (PAR) for low PAR levels and became nearly constant at PAR levels above 200...