Prolonged treatment of potato tubers at 1° C with an atmosphere of pure oxygen eventually induces a marked inhibition of the rate of CO
2
output; there is also an accumulation of pyruvate and of 'citrate’ and a decrease in the contents of
α
-ketoglutarate and of malate as compared with potatoes held in air. These changes in the acids appear to be in accord with the development during sojourn in pure oxygen of a ‘block’ in the tricarboxylic acid cycle between ‘citrate’ and
α
-ketoglutarate. The indications in previous work (Barron, Link, Klein & Michel 1950; Barker & Mapson 1953
b
) that the tricarboxylic acid cycle may operate in potato tubers under certain metabolic conditions are thus supported. The treatment with pure oxygen also results in a progressive shift to the more oxidized state in the ascorbic acid and glutathione oxidation-reduction systems; finally, the potato tissue develops a brown discoloration presumably due to polyphenolase action. The change in the balance of the two oxidation-reduction systems towards oxidation may be caused, in part, by a reduced rate of regeneration of coenzyme II because of the ‘block’ in the tricarboxylic acid cycle. The paper also contains the results of preliminary experiments on the reversibility of the above changes. The data add to the knowledge of the varied metabolic phenomena which have been observed in many different types of living tissue, both plant and animal, and which are conveniently classified under the general term ‘oxygen poisoning’ (Stadie, Riggs & Haugaard 1944).
OXYGEN POISONING
