I don't have access to Carol Reiss's lab manual at the moment but
there is a lot of older potato disc respiration literature online.
The respiration rate in aged discs can be limited by lack of oxygen,
which can reduce any differences between fresh and aged tissue (Figure
4 in MacDonald, 1967). MacDonald (1967) also recommended discs no
greater than 1 mm thickness because diffusion limits oxygen movement
to internal cells.
Temperature also has a major effect on the respiration rate (Figure 5
of MacDonald, 1967). MacDonald (1967, 1968) aged his discs at 25 C for
22 hours and seemed to prefer 30 C for the respiration experiments.
MacDonald, I.R. 1967. Oxygen Tension a Determining Factor in the
Respiration of Potato Disks of Varying Thickness. Plant Physiology 42:
MacDonald, I.R. 1968. Further Evidence of Oxygen Diffusion as the
Determining Factor in the Relation between Disk Thickness and
Respiration of Potato Tissue. Plant Physiology 43: 274-28.
David R. Hershey