Changes in water status of peach flower buds during endodormancy and ecodormancy measured by differential scanning calorimetry and nuclear magnetic resonance spectroscopy

Physiological changes in 'Hakuho' peach [Prunus persica (L.) Batsch] flower buds during endodormancy and ecodormancy were investigated based on their water status measured by differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) spectroscopy. The developmental stage in ecodormancy, which was estimated as the number of days between the sampling date for shoots and the bloom date after forcing, was dominated by absorption of water and was closely related to the water content per dry weight. Two types of water differing in spin-lattice relaxation time (T1) of protons were detected in the flower buds. Water with the shorter T1 was considered to be freezing water as well as that with a longer T1. Nonfreezing water can not be detected by NMR. The change in the longer T1 coincided with the change in the water percentage relative to bud fresh weight and reflected the physiological development in ecodormancy. The shorter T1 value started to increase shortly before rest break and may have some relation with the physiological change at rest break