A technique has been developed for the enzymatic isolation of leaf cells from the Crassulacean acid-metabolism plant Sedum telephium. The cells exhibited high activity in both (14)CO2 incorporation (30-70 μmol CO2 mg(-1) chlorophyll h(-1)) and O2 evolution in the presence of bicarbonate (60-110 μmol O2 mg(-1) chlorophyll h(-1)). Half-maximum saturation of (14)CO2 incorporation occurred at a bicarbonate concentration of ca. 2 mM (20 μM CO2) at pH 8.4 and 30°C. Two types of light-dependent O2 evolution are reported: O2 evolution in the absence of exogenously supplied bicarbonate (endogenous O2 evolution), and bicarbonate-stimulated O2 evolution. Oxygen evolution in the presence of approximately ambient concentrations of CO2 appeared to be a combination of the endogenous O2 evolution and O2 evolution from fixation of the exogenously supplied CO2.