Changes in tissue water content have been correlated, with varying success, with changes in freezing tolerance and dormancy in woody perennials. Recent studies indicate that changes in the state of water are more strongly correlated with dormancy than are changes in bulk water content. In this study, traditional destructive methods of monitoring tissue water content and dormancy were compared with measurements using nondestructive in situ proton nuclear magnetic resonance 1H NMR to determine plant water status. These studies were designed to determine whether changes in bud water status are correlated with dormancy and can be used as a reliable indicator of the onset of dormancy. Two-year-old Vitis riparia plants were subjected to short-day (SD, 8 h daylight) or long-day (LD, 15 h daylight), dormancy-inductive or noninductive treatments, respectively. Bud water was monitored at 2, 4, and 6 weeks of photoperiod treatments. SD treatments promoted a rapid onset in bud dormancy. Water content was not different in SD or LD treatments after 2 weeks. However, it did decrease over 6 weeks in both treatments, but SD treatments promoted a more rapid decrease in water content. The nondestructive 1H NMR methods give comparable measures of water content and provide a measure of bud water status. There were shorter T1 relaxation times in the 2-, 4-, and 6-week SD treatments. The SD treatment T2 relaxation times were shorter in the 4- and 6-week SD treatments only. Changes in the T1 and T2 relaxation times indicated changes in bud water status are correlated with the onset of dormancy.
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