Crassulacean acid metabolism in the Basellaceae (Caryophyllales).

C and crassulacean acid metabolism (CAM) have evolved in the order Caryophyllales many times but neither C nor CAM have been recorded for the Basellaceae, a small family in the CAM-rich sub-order Portulacineae. 24 h gas exchange and day-night changes in titratable acidity were measured in leaves of Anredera baselloides exposed to wet-dry-wet cycles. While net CO uptake was restricted to the light period in well-watered plants, net CO fixation in the dark, accompanied by significant nocturnal increases in leaf acidity, developed in droughted plants. Plants reverted to solely C photosynthesis upon rewatering. The reversible induction of nocturnal net CO uptake by drought stress indicates that this species is able to exhibit CAM in a facultative manner. This is the first report of CAM in a member of the Basellaceae.