EFFECT OF TEMPERATURE ON CARBOHYDRATE CONTENT, ADP GLUCOSE PYROPHOSPHORYLASE, AND ATP-DEPENDENT AND PPI-DEPENDENT PHOSPHOFRUCTOKINASE ACTIVITY OF POTATO-TUBER CALLUS-TISSUE

Callus derived from Lemhi Russet and Russet Burbank tuber tissue was incubated at 20-degrees-C and 30-degrees-C on a high sucrose medium for starch-formation and subjected to simulated storage and reconditioning treatments at 5-degrees-C and 25-degrees-C after transfer of the callus to a medium without a carbon source. Percent dry weight of callus from both cultivars averaged about 21% after starch formation and 5% after storage and reconditioning treatments. Total sugars were higher in callus incubated on the starch forming treatment. Lemhi Russet callus contained predominantly reducing sugars, while Russet Burbank callus contained mostly non-reducing sugars. Total sugar content was generally lower for both cultivars after the storage and reconditioning treatment in callus after starch formation at 2-degrees-C. Starch content was generally higher in Lemhi Russet tissue. After starch formation at 20-degrees-C Lemhi Russet had higher starch after the storage and reconditioning treatment than tissue from 30-degrees-C, while the opposite trend was found in Russet Burbank tissue. Total protein declined in Russet Burbank tissue during the storage and reconditioning treatment regardless of prior incubation conditions, while this decline only occurred in Lemhi Russet tissue initially incubated at 30-degrees-C during the starch formation treatment. In tissue of both cultivars, ATP- and PPi-dependent phosphofructokinase activities were inversely proportional to total sugar concentrations, while in RB callus ADP glucose pyrophosphorylase activities were proportional to starch content.