STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES

XIX. THE MECHANISM OE OXYGEN POISONING OE RESPIRATION IN PEA SEEDS

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Summary

Subjecting peas to high pressures of oxygen produced a progressive decrease in CO2 output with accumulation of citrate, pyruvate, alcohol and acetate (Turner and Quartley, 1956; Pritchard, 1961). The present results show that the progressive decrease in CO2 output in high oxygen was also, in general, accompanied by large and continuing decreases in adenosine triphosphate and in the glycolytic intermediates, dihydroxyacetone phosphate, 3-phosphoglycerate and phosphoenolpyruvate. Fructose diphosphate also decreased more rapidly initially in oxygen than in air in three of the four experiments.

Oxygen poisoning thus appears to ‘block’ partially or completely, certain respiratory pathways, the most important ‘block’ in plant tissues probably being that at aconitase (Pritchard, 1961). The ‘blocks’ are visualized as decreasing both the CO2 output and the rate of formation of adenosine triphosphate. Thus in the present experiments the decreased CO2 output in oxygen was associated with a decrease in content of adenosine triphosphate. The decrease in the content of the latter may in turn reduce the rates of hexokinase and phosphofructokinase phosphoryla-tion and so cause the observed decreases in contents of fructose diphosphate, and, at late stages, of glucose-6-phosphate. The decrease in fructose diphosphate appeared to reduce the rate of glycolysis, as shown by the decrease in the contents of glycolytic intermediates.

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