Changes in sucrose synthetase activities in aging potato tuber slices.

The me-chanism by which the reversible conversion of starch ito sucrose takes place in potato tubers exposed t,o cold is as yet essentilally unknown. Early 'studies on the subjectt tried to correllate this conversion with va,riations in the activity of related enzymes (10). Those responsible for the synthesis of sucrose and sticrose-6--phosphiate (1) are undoubtedly highly relevant. In add'ition to its role in sucrose syntihesis, the sucrose synthetase ilead to the formation of UDP-g;lucose and ADP-glucose (2), the glucosyl donors for starch synthesis catalyzed 'by the particullate (6) and 'the soluble (5) syntheta,se, respectively. As in sweet corn (4), the sugar nucleoltides woulid thu's be the 'link between starch and sucrose syntthetase in potalto tubers. W'it'h the aim of obtaining some ingighit into the regugla.to,ry mechanism of these enzymes we have carried ouit experiments with aging potaato tuber slices, in view of 'the special properties of the itissue in these conditions (3). Potato tubers (Sol(inum tuberosum var. Huincul) were tused. Tissue plugs, 1.5 c'm in diameter, were ctut from tihe central parenchiima with a cork bo'rer. T'he plulgs were sliiced with a microtome inito discls, 1 mm in thickness, which were aged according to Click and Hackett (3). The 'liquid 'of aging was e-ither water or ithe solution dindicated in each case. In prelkiminary experiments, similar resulIts had been obtained by addition of calciuim su,lifate or an'tibiotics to 'the aging medium, or using aeration techniques