Effect of temperature on the sugar content of potato callus tissue

The effects of temperature, incubation time, callus age, and growth regulator on the reducing and nonreducing sugars of Lemhi Russet callus grown on Murashige - Skoog medium with 3% sucrose were determined. Callus grown at 25°C for approximately 4 weeks (0 time) were held at 25°C or transferred to 15°C and 5°C for 4-week periods. Callus grown at 5°C for 4 weeks was transferred back to 25°C for a 4-week period to simulate reconditioning of potatoes. The reducing sugar content decreased rapidly with time at 25°C and 15°C when either 2,4-D or picloram was used as a growth regulator. At 5°C the reducing sugar content increased or decreased slightly, depending on the original reducing sugar content of the callus. The initial reducing sugar content at 25°C and the relative effect of 5°C incubation was dependent on the age of the callus tissue. Reducing sugars in 5°C callus were rapidly lost after reconditioning at 25°C. The nonreducing sugars exhibited similar overall changes as the reducing sugars, but the nonreducing sugar concentrations were much lower. Thus, potato callus cultures are similar to whole tubers insofar as they accumulate or maintain high reducing sugars at low temperatures and lose these sugars during reconditioning.