Are there species in the genus <em>Clusia</em> with obligate C₃-photosynthesis?

Most of the species in the genus Clusia are very flexible in their photosynthetic pathway, and are C-3-photosynthesis/Crassulacean acid metabolism (CAM) intermediate species; therefore, the identification and clear assignment of Clusia-species to C-3- or CAM-pathways is difficult. We made an attempt to characterize obligate C-3-photosynthesis species within that genus. Therefore, we selected five species of the family Clusiacea (four of the genus Clusia and one of the genus Oedematopus) on the basis of their low leaf succulence as potential obligate C-3-photosynthesis species. All of them showed a Cs-photosynthesis pattern of gas exchange under well-watered conditions and their delta(13)C-values were also found to be in the range of obligate C-3-photosynthesis plants. Under drought stress two of them (C. articulata and C. cruiva) proved to be C-3-photosynthesis/CAM intermediate species, while C. parviflora, C, multiflora and most likely O. mirandensis did not show any nocturnal CO2-fixation. However, in C. parviflora and O. mirandensis some nighttime accumulation of malate by internal CO2-recycling might occur. So far, C. multiflora seems to be the only known Clusia species with neither nocturnal net CO2-uptake nor malate accumulation