LEAF BUD ENDODORMANCY RELEASE IN PEACH-TREES - EVALUATION OF TEMPERATURE MODELS IN TEMPERATE AND TROPICAL CLIMATES

A biological test ('single node cuttings' test) was used to study the endodormancy dynamics of the leaf buds of three peach tree varieties i n tropical and temperate climates over 3 years. Results showed evoluti on in the growth capacities of the leaf buds throughout endodormancy i n both climates and it was thus possible to determine dates of endodor mancy release. With these dates and hourly temperature data, the chill ing requirements of the varieties were calculated by different tempera ture models reported in the literature. All these models proved inaccu rate: for each variety, the computed chilling requirement shifted acco rding to the orchard location and year of study. Possible reasons for their inaccuracy are reviewed and discussed.