Measuring Internal Gases and Lenticel Resistance to Gas Diffusion in Potato Tubers

The testing of a simple, non-invasive method for internal atmosphere determination of potato tubers ( Solanum tuberosum L.), which also can be used to determine individual lenticel resistance to gas diffusion, is described. The method involved sampling from a 0.34-ml chamber fixed over a lenticel following equilibration of its contents with the tuber's internal atmosphere. Equilibration time and the lenticel's resistance to gas diffusion were estimated from oxygen or carbon dioxide contents taken at two or more time intervals using first-order rate equations. In mature ‘King Edward’ tubers harvested in 1984 and kept at 5°C and 80% RH for 4 weeks, the mean 99.9% equilibration time of CO 2 content was 4.4 ± 0.75 hr. In a second experiment on mature ‘King Edward’ tubers harvested in 1985 and stored for up to 12 weeks at 4° and 80% RH, the mean 99.9% equilibration time for O 2 content was 6.0 ± 1.17 hr. Repeated rapid sampling from single chambers on tubers increased sample CO 2 contents but had no measurable effect on O 2 contents. Sealing areas of periderm around sampling chambers demonstrated that potato tuber flesh has a significant resistance to gas diffusion, which can give rise to measurable O 2 gradients within undamaged tissue.