Freezing of nonwoody plant tissues: I. Effect of rate of cooling on damage to frozen beet root sections.

Small cylinders of red beet (Beta vulgaris) root were frozen at various rates. Ultraslow cooling at 0.2 C per hour to -4 C produced little damage, as determined by leakage of pigment and electrolytes, and softening. All of these increased at faster rates of cooling or at lower temperatures. Cooling at the ultraslow rate appears to induce extracellular freezing, resulting in a protective dehydration of the cell contents.