The relationship between freezing tolerance and sugar content in cabbage seedlings was investigated. Seedlings exposed to non-freezing low temperature (5 °C) acquired freezing tolerance down to -6 °C. The degree of freezing tolerance increased with duration of exposure to low temperature (up to 10 d). Sucrose, glucose, fructose and myo -inositol were detected as soluble sugars in cabbage leaves, and all soluble sugars, except for myo -inositol, and starch increased gradually during cold acclimation such that their levels were positively correlated with the degree of freezing tolerance. The induced freezing tolerance was attributed not to ontogenetic changes but to cold acclimation. However, the induced freezing tolerance was lost after only 1 d of deacclimation at control temperatures, and this change was associated with a large reduction in sugar content.

These results reveal that the sugar content of cabbage leaves is positively correlated with freezing tolerance.

November 28, 1995 ; March 29, 1996