EVALUATION OF WINTER CLIMATE FOR BREAKING BUD REST USING THE DYNAMIC MODEL

A model aimed at explaining the complex effects of temperatures on completion of rest in peach buds was developed.
It was termed the dynamic model and is unique as it analyzes the direct temperature effects but also considers the modifying effects of temperatures before and after the specific exposure.
The model was developed on the basis of former published experimental data and is based on a two step scheme.
The first step produces a reversible intermediate and the second one fixes the effect by an irreversible transition.
The rate constant of the first step are assumed to depend on temperature according to the Arrhenius law.
Mathematical analysis of the dependence of the intermediate level with time reveals a curve that follows an asymptotic function.
The higher the temperature the lower the intermediate maximal level.
The irreversible transition is assumed to occur only when a critical mass of the intermediate is reached.
This occurs only after exposure to low temperatures.
Once this transition takes place, an accumulation of one portion occurs and a renewed accumulation of the intermediate may follow.
A computer program was developed on the basis of the dynamic model with suggested parameters from a simulated work.

The model agrees well with the following effects: The bell shape dependence on temperature for rest completion; the negation of the chilling effect by high temperatures; the dependence of the negation effect on the cycle length; the dependence of the negation effect on the level and duration of exposure to high temperature; and the enhancement effect of short exposure to moderate temperatures in daily cycles.
Predictions of the dynamic model that long diurnal

International Workshop on Apple Culture in the Tropics and Subtropics

A. Erez, S. Fishman, Z. Gat, G.A. Couvillon

https://doi.org/10.17660/ActaHortic.1988.232.10