Comparative measurements of gas-exchange, acid accumulation and chlorophyll a fluorescence of different species of Clusia showing C-3 photosynthesis, or crassulacean acid metabolism, at the same field site in Venezuela

Abstract

Four different Clusia species showing C3 photosynthesis (C. multiflora) or crassulacean acid metabolism (CAM) (C. rosea, an unidentified Clusia sp. and C. alata) co-occur in the same habitat in the northwest of Venezuela. The aim of this field study was to correlate the adaptive changes in chlorophyll a fluorescence with gas exchange patterns and deacidification of nocturnally accumulated organic acids. The results indicate that in C. rosea and Clusia sp. a lowering of the potential quantum yield, measured as Fv/Fm after 10 min of dark adaptation, is restricted to the early morning hours. With the onset of deacidification there was no further decline in Fv/Fm, although the irradiance upon th..