Changes in the potato (Solanum tuberosum L.) tuber at the onset of dormancy and during storage at 23 degrees C and 3 degrees C. I. Biochemical and physiological parameters

In the last 30 d of potato (Solanum tuberosum L.) tuber growth metabolic ac tivity decreased. Levels of glucose-6-P and sucrose in whole tuber tissues declined and in tuber slices there was a decrease in the uptake from the me dium and in the incorporation into macromolecules of [U-C-14]sucrose. Durin g storage at 23 degrees C only the uptake of [U-C-14]sucrose increased conc omitant with tuber sprouting, indicating a possible involvement of the tran sport mechanisms in dormancy breaking. At 3 degrees C, levels of reducing s ugars and sucrose increased in response to the low temperature and increase d release of K+ and malondialdehyde levels indicated cell membrane damage. The cell membrane functionality was restored at sprouting. The sprouting po tential of the tubers was evaluated using the sprouting ability of single-b ud explants ("seedcores") in response to water, GA(3) or ABA dips. This spr outing potential of tubers changed with stage of tuber growth and storage d uration and temperature, indicating that the tissue hormonal state changed strongly throughout tuber life, probably in relation with the "sink" to "so urce" transition.