BUD BREAK DELAY ON SINGLE NODE CUTTINGS AND BUD CAPACITY FOR NUCLEOTIDE ACCUMULATION AS PARAMETERS FOR ENDODORMANCY AND PARADORMANCY IN PEACH-TREES IN A TROPICAL CLIMATE

Two tests, one biological the other biochemical, were used to determine the nature of growth inhibition during 'winter' rest of leaf buds of peach trees cultivated in the tropical climate of Reunion Island. The 'cuttings' test measures the growth capacity of the bud attached to a shoot segment and thus may reveal either paradormancy or endodormancy. The 'nucleotides' test, which determines the ability of the bud alone to increase its nucleoside triphosphate pool subsequent to an exogenous supply of adenosine, is a marker of endodormancy. Results show that, although it is only of slight intensity, endodormancy does occur in buds in a tropical climate. They also show that what is recorded as bud growth inhibition can be paradormancy at the beginning of the rest period and endodormancy later, which supports the idea that endodormancy is the result of a gradual shift of the sources of growth inhibition from the shoot to the bud itself. They finally suggest that the reverse sequence could occur with dormancy release and that long-range inhibitions could be the cause of erratic budbreak under a tropical climate.