More recent studies show that " it is highly unlikely that significant carbon assimilation occurs in the stem "; " Pereskia " species are described as having " C 3 with inducible CAM . " Leafless cacti carry out all their photosynthesis in the stem, using full CAM ., it is not clear whether stem-based CAM evolved once only in the core cacti, or separately in the opuntias and cactoids; CAM is known to have evolved convergently many times.
