Consequently plants subjected to a bright morning of direct sunlight after a heavy freeze will show freeze damage. Plant Mechanisms of Frost Resistance Plants have several mechanisms by which they tolerate freezing temperatures. The ability of plant and animal cells not to freeze at temperatures below 32 degrees F is called supercooling. This phenomenon has been found in many hardwoods and dormant buds. Some plant cells were found not to freeze until the temperature dropped as low as about -40 degrees F. Plant cells can be supercooled to relatively low temperatures if ice nucleation does not occur.
Ice nucleating agents promote the initiation of ice formation.
Once initiated, the ice formation spreads rapidly. In an experiment on peach trees, ice spread through the entire tree in 16 minutes. The ability of plants to supercool varies from species to species and from month to month. In tree fruits, the buds had no ability to supercool in September and October, but developed the ability by November and again lost the ability as early as January or as late as April, depending on the species. What becomes apparent in examining the way that plant mechanisms of freeze resistance are induced is that these physiological process are time dependent.