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 activity 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 medium and in the incorporation into macromolecules of [U-14C]sucrose. During storage at 23 °C only the uptake of [U-14C]sucrose increased concomitant with tuber sprouting, indicating a possible involvement of the transport mechanisms in dormancy breaking. At 3 °C, levels of reducing sugars and sucrose increased in response to the low temperature and increased release of K+ and malondialdehyde levels indicated cell membrane damage. The cell membrane functionality was restored at sprouting. The sprouting potential of the tubers was evaluated using the sprouting ability of single-bud explants ('seedcores') in response to water, GA3 or ABA dips. This sprouting potential of tubers changed with stage of tuber growth and storage duration and temperature, indicating that the tissue hormonal state changed strongly throughout tuber life, probably in relation with the 'sink' to 'source' transition.