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Title: WATER STATUS AND RELEASE FROM DORMANCY IN BLUEBERRY FLOWER BUDS

Author
item PARMENTIER, CECILE - CONTRACT EMPLOYEE
item Rowland, Lisa
item Line, Michael

Submitted to: American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Other investigators have previously reported that water is in a more bound form while woody perennial plants are dormant and is converted to a freer form at the time the chilling requirement is satisfied. Therefore, the status of water could provide clues to scientists as to the mechanism of dormancy development in woody perennials. Experiments were conducted to evaluate the changes in water status of blueberry flower buds, using Nuclear Magnetic Resonance, along with the changes in dormancy. Whatever the cultivar (Bluecrop, Gulfcoast, Tifblue), the state of water as well as the water content did not change with chilling accumulation. Satisfaction of the chilling requirement was not enough to free water. On the other hand, a transition from bound to freer water occured if the plants were placed under forcing conditions (24 degrees C, long day) after they had received enough chilling to satisfy their chilling requirement. The results suggested that bound water is more associated with cold hardiness than with dormancy. NMR can be developed as a tool for scientists to distinguish buds that are strictly dormant (before satisfaction of the chilling requirement) from buds whose inability to break is imposed by the environmental factors (not enough warm temperature).

Technical Abstract: Other investigators have previously reported that water is in a more bound form while woody perennial plants are dormant and is converted to a freer form at the time the chilling requirement (CR) is satisfied. Therefore, the status of water could provide clues to scientists as to the mechanism of dormancy development in woody perennials. Three blueberry (Vacciunium section Cyanococcus) genotypes, that have different CRs and levels of cold hardiness, were studied. Dormancy was evaluated and water status determined, using Nuclear Magnetic Resonance, throughout the accumulation of chilling that leads to release from dormancy. Among the cultivars studied, 'Bluecrop'(Vaccinium corymbosum) was the most dormant, 'Gulfcoast' (Vaccinium corymbosium x Vaccinium darrowi) was the least dormant, and 'Tifblue' (Vaccinium ashei) was intermediate. The NMR results showed that 'Bluecrop' buds had the lowest relaxation times (T2), indicating that water was relatively more bound in 'Bluecrop' than in the two other cultivars. Whatever the cultivar, no significant variation of T2s and water content of the buds was noted throughout the accumulation of chilling, even after CRs were satisfied. Within one day of forcing (24 degrees C, long day), there was a shift towards more free water but no change in the water content. Forcing was ineffective in freeing water before the CR was satisfied. Results suggested that bound water is more associated with cold hardiness than with dormancy.