Chlorophyll Fluorescence and Organic Acid Oscillations during Transition from CAM to C3-photosynthesis inClusia minor L. (Clusiaceae)

In species of Clusia, switching from C₃-photosynthesis (C₃-PS)to crassulacean acid metabolism (CAM) may be a means of optimizingwater use, plant carbon balance and photon utilization duringperiods of stress. We ask whether, in perennial species of Clusia,the switch from CAM back to C₃-PS is also of ecophysiologicalsignificance. Our objective was to investigate the performanceof C. minor L. during a short-term shift from CAM to C₃-PS.During the transition from CAM to C₃-PS, nocturnal malate andcitrate accumulation decreased whereas CO₂uptake increased duringthe daytime. However, after 7 d, marked nocturnal accumulationof citrate and 24 h CO₂uptake occurred. In contrast to C₃-likephotosynthesis, a pronounced reduction in the effective quantumyield of photosystem II,