ISHS Acta Horticulturae 276: II International Symposium on Computer Modelling in Fruit Research and Orchard Management
THE DYNAMIC MODEL FOR REST COMPLETION IN PEACH BUDS |
| Authors: | A. Erez, S. Fishman, G.C. Linsley-Noakes, P. Allan |
| DOI: | 10.17660/ActaHortic.1990.276.18 |
| Abstract:
A model describing the response of dormant buds in deciduous fruit trees to temperature was developed. The model is based on observations on dormancy breaking under controlled conditions. It assumes that the level of dormancy completion depends on the level of a certain dormancy breaking factor which is accumulated in buds by a two-step process. The first step is assumed to be a reversible process of formation and destruction of a thermally labile precursor. When a critical portion of the precursor is amassed, it is transferred irreversibly in the second step to one portion of a stable factor. The dynamics of this process simulate development during dormancy and agree with the complex effects of temperature on rest completion. The following effects were described by the model: 1. The optimum bell shaped curve of the rest breaking dependence on temperature with maximum efficiency at 6°C and zero effect at -2°C and 14°C. 2. Negation of the chilling effect by high temperatures depending on their level, duration and cycle length when alternating with lower temperatures. 3. Enhancing effect of moderate temperatures on chilling when they alternate with chilling temperatures. A computer program for simulation of the dormancy completion process was developed. The program is written in FORTRAN and is easily accessible with most computers. Simulation of dormancy breaking under cycled temperature condition was carried out using the STELLA program (High Performance Systems, Inc. developed for simulation of dynamic phenomena for the Apple Macintosh). The graphs generated during the simulations are presented in this communication. The Dynamic model was compared with the Chill-Units model, developed in Utah, for five locations in South Africa during winter 1988. A good correlation of the two models was found for the coldest region whereas in warmer ones the results of the two models diverge; the warmer the location the greater the difference. The | |
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