Use of 1H-NMR to Determine Grape Bud Water State during the Photoperiodic Induction of Dormancy

Nuclear magnetic resonance longitudinal (T 1 ) and transverse (T 2 ) times were used to monitor changes in bud water state during the photoperiodic induction of dormancy in grape ( Vitis riparia Michx.). Short day (SD) treatments were used to promote a rapid onset of bud dormancy, and long day (LD) treatments were used to prevent the onset of dormancy. Water content (WC) and the state of bud water were monitored after 2, 4, and 6 weeks of LD or SD treatment in three bud developmental stages. There was no difference in WC in the SD and LD treatments after 2 weeks. WC decreased in LD and SD buds of all stages during the 6 weeks of treatments, but there was a greater decrease in WC in SD treatments. The state of bud water changed during the SD treatments, shown in changes in T 1 and T 2 relaxation times. The SD T 1 relaxation times were shorter than the LD T 1 values at all measurement times. The SD T 2 times were shorter than the LD T 2 values in the 4- and 6-week treatment only. Tissue age was an element in lowering the T 1 and T 2 times but not the primary factor. A comparison between the bud dormancy response in the SD and LD treatments and the relaxation times showed that the shorter relaxation times indicate a restriction of motional freedom. The short relaxation times of the SD treatment correlated with the onset of dormancy. When dormancy is fully induced, T 2 times correlated better with dormancy than T 1 times.