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- Author or Editor: D. J. Rowse x
Deep supercooling in Prunus flower buds was related to vascular development. The continuity of the xylem was monitored by following the movement of a water-soluble dye. Dye was translocated into the primordia of 3 Prunus species which do not supercool, but it was not observed to move into the primordia of 11 species which avoid freezing injury by deep supercooling. Dye uptake may provide a simple and inexpensive technique to screen for bud supercooling.
The freezing of water within the woody tissues of apricot (Prunus armeniaca L.) and peach [Prunus persica (L.) Batsch] was characterized and the relationship to freezing injury established. Bark and xylem tissues exhibited contrasting freezing patterns and mechanisms of freezing resistance. Water in xylem parenchyma cells deep-supercooled. Tissue injury appeared to result from the freezing of this supercooled water. In contrast, water within bark tissues underwent equilibrium freezing. Bark injury resulted from the stresses which accompany extracellular ice formation and cellular dehydration.
A method for large scale evaluation of flower bud hardiness in apricots using a thermal analysis system interfaced to a computer is described. The technique measures the heat released during the lethal freezing of supercooled water within the bud primordia. Nine thermoelectric junctions wired in series were used to monitor the temperature of 10 individual buds. Bud temperature was scanned every 30 seconds and the data recorded on magnetic tape. The data were subsequently transferred to a minicomputer which analyzed and stored data and produced graphics. Computer assisted thermal analysis can accommodate a large number of samples and simplifies handling and storage of data. This technique has applications as a research tool, for determining critical bud temperatures and in screening selections from a breeding program.