Turnover Rates of Phosphate Esters in Fresh and Aged Slices of Potato Tuber Tissue.

In recent years, a number of studies have been miadle on the respiration of slices of potato tuber tissue (1, 6, 7, 8, 9, 11, 12, 13, 16, 17). \VXhen the slices or dlisks are freshly cut, they have a respiration rate sinmilar to that of the intact tuber. This tissue lhas been termed fresh tissue. \Vhen the fresh disks are kept by aerating them in distilled water or 10-4 Al CaSO4 at 00, the low respiration rate is maintained: but when the disks are aerated at 250, the respiration rate rises threeto fourfold over about 18 hours. This phenomenon has been termled aging, and (lisks treated in this way are aged disks. Aging does not mlerely involve a simple increase in respiration rate: the sensitivity of the respiration to various inhibitors alters markedly (1, 6, 11, 16, 17), andl the tissue shows a marked increase in its ability to accumiiulate salts, particularly phosphate (6, 9, 13). Such observations have led to suggestions that aging involves a major change in the cellular processes (7). Some authors (6, 17) have suggested that there is a mlodification of the respiration chain in the region between DPNH and cvtochronme c: while others ( 1, 16) have suggested that there are chainges in the relative importance of the pentose phosphate and the tricarboxylic acid cycle respiration paths. The results of experimlents by Loughmani (9) indicate that the respiration changes are closely associate(l with changes in the phosphate mletabolismii. Therefore experiments have been carried out to examine in more detail the phosphate metabolism of fresh and aged potato tuber slices, with a view to learning more about the nature of the aging process.