Rapid-cycling CAM; an hypothetical variant of photosynthetic metabolism

Abstract

The currently recognized forms of CAM photosynthesis do not represent all possible variants on the theme. It is predicted here that there may exist an undiscovered variant in which the CO2-acquiring and CO2-reducing phases of CAM alternate over time periods shorter (possibly much shorter) than the diel cycle. The process would occur entirely in the photoperiod and may be likened to a form of C4 photosynthesis in which the same photosynthetic cell alternates between performing the functions of a C4 mesophyll and C4 bundle sheath cell. Rapid-cycling CAM, which would be unlikely to be detected by methods commonly used to measure photosynthesis, could provide a CO2-concentrating mechanism in both unicellular and multicellular plants.