Oxygen and carbon isotopic compositions of gases respired by humans and plants

Abstract

Oxygen isotope fractionations has been observed in human and plant respiration which bears a linear relationship to the fraction of the O_2 utilized in the respiration process. In the case of humans there appears to be a characteristic slope for this relationship for different individuals at rest, as well as being affected by exercise, by the level of hemoglobin and by the history of smoking.

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