Supercooling and heterogeneous nucleation of freezing in tissues of tender plants.

The extent to which tissue pieces of several frost tender plant species could be supercooled in the absence of external sources of ice nucleation was determined in a small cold chamber. A considerable range among plant species was revealed in their ability to supercool. This could be expressed as a differential nucleus spectrum that derives the minimum concentration of nucleating sites within the samples. French bean (Phaseolus vulgaris L.) was found to contain nucleators effective in the range ?4 to ?8 °C, whereas spring wheat (Triticum aestivum L.) contained sites active between ?8 and ?16 °C. The data indicate that these plant samples can supercool to temperatures below those normally injurious to them when they are frozen.