The  pathway bears resemblance to CAM; both act to concentrate  around RuBisCO, thereby increasing its efficiency. CAM concentrates it temporally, providing  during the day, and not at night, when respiration is the dominant reaction.  plants, in contrast, concentrate  spatially, with a RuBisCO reaction centre in a "bundle sheath cell" being inundated with . Due to the inactivity required by the CAM mechanism,  carbon fixation has a greater efficiency in terms of PGA synthesis.
There are some /CAM intermediate species, such as Peperomia camptotricha, Portulaca oleracea, and Portulaca grandiflora. It was previously thought that the two pathways of photosynthesis in such plants could occur in the same leaves but not in the same cells, and that the two pathways could not couple but only occur side by side. It is now known, however, that in at least some species such as Portulaca oleracea, C and CAM photosynthesis are fully integrated within the same cells, and that CAM-generated metabolites are incorporated directly into the C cycle.