Use of crop simulation to evaluate antitranspirant effects on tomato growth and yield

Maximum crop production is closely related to the availability of water Tra nspiration may be reduced by the application of an antitranspirant (AT) tha t would increase leaf resistance to diffusion of water vapor: Our objective was to determine the effectiveness of one of the most promising antitransp irants, Vapor Gard(TM), on tomato production in Florida. An experiment with three treatments, control plants with no AT application, sprayed with AT o nly before flowering, and sprayed with AT before flowering, at fruit initia tion and after first harvest, Mins conducted at Bradenton, Florida, in 1997 . A dynamic, greenhouse tomato, growth and yield model was modified and use d to characterize how different plant growth processes are affected by anti transpirant. Parameters in the model were estimated by minimizing sum of sq uares of error between simulated and observed data for each treatment. Root mean square errors for number of main stem nodes, leaf area index, total a bove ground biomass and fruit dry weight averaged 0.48, 0.17, 35.68g m(-2), and 81.26 g m(-2), respectively, demonstrating a close Jit 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. Ther e was no effect on fruit yield. Mast of the vegetative growth response coul d be explained by an increase in plant temperature likely caused by reduced transpiration by the AT treated plants.