Respiration of sugar-beet leaves during illumination, with simultaneous photosynthesis

The intensity of respiration and of photosynthesis were investigated simultaneously in sugar-beet leaves not detached from the plant. Several hours before the experiment the leaves had assimilated radioactive14CO2 whereafter they were placed into a normal leaf chamber for continuous gasometric estimation of the intensity of photosynthesis, according to the changes in the concentration of carbon dioxide in the passing air. At the same time, the specific activity of C02 was measured in the air that had passed through the assimilation chamber. From the values of the specific activity of CO2 produced by the leaf in the dark the intensity of respiration in mg. CO2 can be calculated.