ISHS Acta Horticulturae 395: Dormancy and the related Problems of Deciduous Fruit Trees
TEMPERATURE AND STRESS EFFECTS ON REST IN FRUIT TREES: A REVIEW |
| Author: | Gary A. Couvillon |
| Keywords: | Rest, dormancy, endodormancy, chilling temperatures, chilling negation, growing degree requirement for bud break, heat requirement |
| Abstract:
Certain fruit species require low temperature exposure (chilling) for normal and abundant bud break to occur in the spring. Chilling temperatures are not effective in satisfying the rest requirement until a significant amount of leaf fall has occurred in the fall. The most efficient continuous temperature for satisfying the rest requirement is 8C. Temperatures above 8C are less effective and all chilling effectiveness is loss with temperatures above 12C. On the other hand, temperatures between 8C and 4C are effective chilling temperatures, but are less effective than 8C and temperatures below 4C are moderately effective. If moderate temperatures (i.e. 13–15C) are interspersed, for 8 hours in a 24 hour cycle, with chilling temperatures, the chilling efficiency of the low temperature is enhanced. On the other hand, high temperatures (i.e. 19C or higher), interspersed in the same manner, will result in chilling negation. The degree of negation will depend upon the level and length of the high temperature exposure period. However, short periods (2 to 4 hours) of 20C in a diurnal cycle can enhance the chilling effect of the low temperature. Only that chilling accumulated 20 to 40 hours prior to the onset of high temperatures is susceptible to high temperature negation. Post rest chilling reduces the heat requirement for bud break. It seems that high temperatures can replace the need for chilling, especially in cultivars with a short chilling requirement. | |
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