Changes in water status in peach buds on induction, development and release from dormancy

Peach shoots collected prior to onset of chilling in early November from mid Georgia, were exposed to short days or cold temperature to induce dormancy. A gradual increase in bound water under both conditions was found in comparison to control left under warm long days condition. To release dormancy, buds were exposed to 0 or 4 degrees C, temperature that break dormancy, acid to a 6-24 degrees C, diurnally cycled treatment that prevents chilling accumulation, and is inefficient in breaking dormancy. Chilling temperatures (0 and 4 degrees C) induced somewhat freer water after 39 days than the 6-24 degrees C treatment. The proportion of free water increased until 55 days. When shoots were transferred to forcing conditions, a further rapid increase in free water was noted especially with shoots that were exposed to chilling previously. The conversion of bound to free water on exposure to forcing conditions was also verified with orchard-chilled peach buds. Buds on branches that were not exposed to effective chilling were also showing the appearance of free water after exposure to high temperatures for a long duration. Evaluating these data raises the possibility that bound water in buds of temperate fruit trees is correlated with the level of cold resistance rather than with the level of endo-dormancy. This may explain the much higher levels of freer water during dormancy in the less cold-resistant peach than in the more cold-resistant apple. (C) 1998 Elsevier Science B.V.