Expression of Modes of Photosynthesis (C₃, CAM) in <i>Clusia criuva</i> Camb. in a CerradolGallery Forest Transect

Abstract

Abstract: The large majority of the Ca . 150 species of the neotropical shrub and tree genus Clusia have the potential to perform Crassulacean acid metabolism (CAM). They are either obligate CAM plants or C 3 /CAM intermediate plants. Only a very small percentage of the plants studied so far are apparently obligate C 3 species. Among these was C. criuva , until recent laboratory studies showed that it may also have a certain CAM capacity under artificial stress conditions. Measurements of stomatal conductance (porometry) and chlorophyll fluorescence variables of C. criuva occurring along a transect from deep shade inside a gallery forest across the semi‐shaded ecotone towards a cerrado and into the exposed cerrado itself in central Brazil now show that it can adapt its photosynthetic apparatus to effective performance of C 3 photosynthesis under highly different photosynthetic photon flux densities. In addition, however, it does have a certain potential for CAM and cannot be considered as a strictly obligate C 3 plant. Should a basic capacity for performing CAM be a general property of the genus, the quest for CAM traits in other remaining putatively obligate C 3 species of the genus ought to be pursued.