Laboratory of Plant Physiology, Biochemistry and Biotechnology, Department of Biology and Department of Biochemistry and Molecular Biology, University of Minnesota Duluth, Duluth, MN, 55812, USA.
Photosynthesis is a process by which plants remove CO2 and add oxygen to the atmosphere, thereby regulating the atmospheric ratio of CO2 and O2 concentrations. In Nature, the CO2 and O2 equilibrium is determined by photosynthesis through CO2 fixation and CO2 evolution, by O2 fixation and O2 evolution, and by short and long-term storage of CO2 by plants and algae. These processes are integrated in this paper through a revised total photosynthetic carbon cycle. The changes to the existing paradigm are physiological consequences from the simultaneous, dual activities of Rubisco. The dual activities of Rubisco limit net photosynthesis and the ratio of CO2 to O2 concentrations. A minimal CO2 level with 21% O2 and a maximal O2 concentration with a constant CO2 level, are defined as Rubisco CO2 and O2 compensation points (Γ). These modifications of photosynthetic carbon metabolism are proposed for understanding net plant growth and regulation of the atmosphere.
C2 cycle, C3 cycle, C4 cycle, Oxygen compensation point, PEPcase, Rubisco
