The Frost Hardiness of Several Solanum Species in Relation to the Freezing of Water, Melting Point Depression, and Tissue Water Content

Pulsed nuclear magnetic resonance spectroscopy was used to study the freezing process in excised leaf tissues of several Solanum species. The amount of liquid water in the partially frozen leaf tissues at the killing temperature was 41%-47% in susceptible genotypes of S tuberosum, 43% in `Alaska Frostless,' and 22%-36% in other more hardy species. The excised leaf tissues of all species froze as ideal solutions. There were no correlations between frost killing temperature and tissue water content or the melting point depression of cell sap The major difference between the tender and hardy tissues was the ability of hardy tissue to tolerate more frozen water at frost killing temperatures