USE OF CROP SIMULATION TO EVALUATE ANTITRANSPIRANT EFFECTS ON TOMATO GROWTH AND YIELD
Maximum crop production is closely related to the availability of water. Transpiration may be reduced by the 
application of an antitranspirant (AT) that would increase leaf resistance to diffusion of water vapor. Our objective was to 
determine the effectiveness of one of the most promising antitranspirants, Vapor Gard™, on tomato production in 
Florida. An experiment with three treatments, control plants with no AT application, sprayed with AT only before 
flowering, and sprayed with AT before flowering, at fruit initiation and after first harvest, was conducted at Bradenton, 
Florida, in 1997. A dynamic, greenhouse tomato, growth and yield model was modified and used to characterize how 
different plant growth processes are affected by antitranspirant. Parameters in the model were estimated by minimizing 
sum of squares of error between simulated and observed data for each treatment. Root mean square errors for number of 
main stem nodes, leaf area index, total above ground biomass and fruit dry weight averaged 0.48, 0.17, 35.68g m–2, and 
81.16 g m–2, respectively, demonstrating a close fit of the observed data. By using the model, alternate hypotheses to 
describe the effects of AT on growth processes were evaluated. It was found that the main effects of AT treatments on 
tomato plants were on node development and LAI growth, as indicated by differences in model parameters for these two 
variables. There was no effect on fruit yield. Most of the vegetative growth response could be explained by an increase in 
plant temperature likely caused by reduced transpiration by the AT treated plants.