Dormancy Effects on Supercooling in Deacclimated `Meteor' Tart Cherry Flower Buds

Abstract

Exposure of `Meteor' tart cherry (Prunus cerasus L.) flower buds to deacclimating conditions resulted in an increase in the temperature of the low-temperature exotherms (LTEs) produced by the flower primordia during controlled freezing. Primordium supercooling temperature was related to chill unit accumulation, an indicator of depth of flower bud endodormancy. LTEs ceased to be detected after deacclimation earlier in 1986-87, a season of more rapid chill unit accumulation, than in 1987-88. Before deacclimation, the range of primordium LTE temperatures within a flower bud was normally ≤1C, but in deacclimated buds considerable variability in LTE temperatures was observed. However, primordia within a flower bud lost the ability to supercool simultaneously. This change was generally concurrent with the appearance of mature xylem vessel elements (XVE) in the upper bud axis and in the flower primordium but did not entirely depend on vessel element maturation.