Growth and oxygen uptake of potato callus is faster in an oxygen-enriched atmosphere (70% oxygen, v/v; "oxygen-callus") than in air (20% oxygen, v/v; "air-callus"). Especially the non-mitochondrial, so-called 'residual respiration' is increased in "oxygencallus". The capacities of the mitochondrial respiratory pathways (cytochrome pathway, Vcyt and alternative pathway, Va]t) are also higher in this callus. In both callus types only a small part of the alternative pathway capacity is used in uninhibited respiration. The lower oxygen uptake of "air-callus" at normal air oxygen pressures is partially due to diffusional impedance. Measurement of the respiratory parameters of "air-callus" in oxygen-saturated medium leads to higher values than measurement in air-saturated medium, although these values are still lower than those of "oxygen-callus".
ATP-production was calculated from the oxygen-uptake data and compared with the dry weight production of the callus to give values of 10.0 and 10.8 g dry weight produced.mol ATP-[, for "air-callus" and "oxygen-callus" respectively. As no harmful side-effects are observed, cultivation of callus under elevated oxygen pressures may be useful, when rapid callus-growth is necessary.