Supercooling Characteristics of Isolated Peach Flower Bud Primordia

The amount of unfrozen water in dormant peach (Prunus persica [L.] Batsch, cv Redhaven) flower buds, isolated primordia, and bud axes was determined during freezing using pulse nuclear magnetic resonance methods. Differential thermal analysis studies were conducted on whole buds and isolated primordia in the presence of ice nucleation. The results showed that some of the water in isolated primordia remained supercooled in the presence of ice nucleation. Although most tissue water froze (57.5%) following ice nucleation at -2.5 degrees C, a considerable amount of water was found to supercool. In the presence of ice nucleation, increased hydration of isolated primordia resulted in the elimination of the supercooling characteristic. The structural integrity of isolated primordia appeared to be essential for supercooling.