Metabolic heat rate and respiratory substrate changes in aging potato slices

Potato tubers (Solanum tuberosum L. cv. Russet Burbank) were cut into slice s 1 mm thick. Tissue was placed in sealed ampules in a calorimeter operated isothermally at 25 degrees C, The metabolic heat rate began to increase wi thin 2 h after slicing, reaching a maximum after 30 h. The peak heat rate w as six times that of the initial rate. Heat production was cyanide-sensitiv e at first while that which developed with time was largely cyanide-insensi tive. The initial heat rate per oxygen consumed increased to a peak value, indicating greatly reduced energy conservation. The ratio of CO2 produced t o O-2 consumed, together with the CO2 rate/heat rate indicated a change fro m more reduced to more oxidized substrates, i.e. from lipid to starch, Calo rimetric results were in good agreement with published results obtained wit h other methods. (C) 2000 Elsevier Science B.V. All rights reserved.