Light-Stimulated Burst of Carbon Dioxide Uptake following Nocturnal Acidification in the Crassulacean Acid Metabolism Plant Kalanchoë diagremontiana

CO(2) exchange characteristics were studied during the light-stimulated burst of CO(2) uptake (MB) immediately following a period of nocturnal CO(2) fixation in the Crassulacean acid metabolism plant Kalanchoë daigremontiana. During the early parts of the MB, stimulation of net CO(2) uptake by low ambient O(2) concentration (1.5%) was small, and leaves showed the capacity for net CO(2) uptake at low ambient CO(2) partial pressure (30 microbars) and when the MB was interrupted by darkness. During the later phase of the MB, stimulation of net CO(2) uptake by 1.5% O(2) was increased, and net CO(2) loss was recorded both at 30 microbars CO(2) and during dark interruptions. These results suggest that CO(2) fixation during the MB occurs simultaneously via phosphoenolpyruvate carboxylase (predominant during the early phase of the MB) and via ribulose bisphosphate carboxylase (predominant during the later phase of the burst). The magnitude and duration of the MB was increased by a reduction in the length of the dark period and by low (15 degrees C) compared to high (30 degrees C) leaf temperatures.