INTRODUCTION OF SPECIFIC CARBOHYDRATES INTO EUCALYPTUS-GUNNII CELLS INCREASES THEIR FREEZING TOLERANCE

The comparison of soluble sugar content in various cell lines of Eucal yptus gunnii exhibiting different freezing resistances revealed that t he most resistant cell line contained the highest soluble sugar conten t. It was possible to increase the freezing resistance of the sensitiv e cell line by progressive exposure to low temperatures (acclimation). During the early stage of cold acclimation, an increase of soluble su gar concentration was observed in the cells confirming the correlation between freezing resistance and soluble carbohydrate content in this species. In addition, feeding experiments on the sensitive cell line w ere performed to introduce specific sugars into the cells. Both electr opulsation and long-term incubation in the presence of fructose and ra ffinose led to an increase in the tolerance of the cells during a free zing programme. Using radioactive fructose, the uptake of the sugar in to cells and protoplasts was checked. In the light of these results, h ypotheses are presented concerning the possible role of intracellular sugars in cryoprotection.