Photosynthesis and CO2 evolution by leaf discs: gas exchange, extraction, and ion-exchange fractionation of 14C-labeled photosynthetic products

A leaf chamber is described which allows the measurement of the gas exchange of leaf discs in an open gas analysis system. Pretreatment of the leaf discs with nitrogen and inclusion of moist filter paper in the leaf chamber resulted in rates of photosynthesis that were constant for 40 min and equal to 60 to 70% of the rate of photosynthesis measured in intact leaves. Analysis of the products of 14CO2 fixation from whole leaves and leaf discs and a comparison of the gas exchange under various conditions established that the leaf discs accurately reflected the metabolism of the attached leaves.