Properties of peach flower buds which facilitate supercooling.

Water in dormant peach (Prunus persica [L.] Batsch. var. ;Harbrite') flower buds deep supercooled. Both supercooling and the freezing of water within the bud axis and primordium as distinct components depended on the viability of the bud axis tissue. The viability of the primordium was not critical. Supercooling was prevented by wounding buds with a dissecting needle, indicating that bud structural features were important. Bud morphological features appeared to prevent the propagation of ice through the vascular tissue and into the primordium. In dormant buds, procambial cells had not yet differentiated into xylem vessel elements. Xylem continuity between the bud primordium and adjacent tissues did not appear to be established until buds had deacclimated. It was concluded that structural, morphological, and physiological features of the bud facilitated supercooling.