Growth model of greenhouse tomatoes with carbon dioxide enrichment : development and experimental tests

Abstract

A deterministic, compartmental growth model of greenhouse tomato plants, written in Pascal computer language, was developed based on a leaf assimilation model and a model of a theory that the photosynthesis rate is controlled both by the environmental conditions and by the internal carbohydrate level in the leaf. The model was tested with data obtained from two experiments conducted in 1983 through 1984 at College Station, Texas. Three 2m x 2m x 10 m chambers were built in a plastic-covered greenhouse, and tomato plants were grown in the chambers at three different CO2 concentrations: 340, 700, and 1000 μm^3/m^3. Inputs to the model were the light and CO2 levels and the air temperature. The outputs included the CO2 assimilation rate, dry-mass accumulation rate, and tomato yield, which were compared with the results from the measurements. The model underestimated CO2 assimilation rate and dry-mass accumulation rate of tomatoes for all CO2 levels; however, it predicted the fruit growth and yield rather accurately. For a growth model with parameters taken not from the measurements, but from earlier published results, the magnitude and trend of the results of the simulation were reasonably acceptable. A potential use of the model is to predict the effects of environmental factors or to estimate the benefit from CO2 enrichment under different environmental conditions. It also can be a part of an integrated greenhouse model which predicts growth and yield of the crop in the greenhouse using the environmental conditions outside the greenhouse and the greenhouse control mechanisms and strategies.