Under which conditions is the C4metabolic pathway favored? : When does the C4 metabolic pathway become less costlythan the C3 metabolic pathway?

Abstract: C4 photosynthesis is an advanced complement to the more ancestral and more commonpathway refereed to as C3. C4 metabolism has evolved in several taxa, and it is theorized thatit worked as an adaptation to the low CO 2 levels characteristic of late geological time. Theadaptation also carries with it some resistance to the negative effects brought on by hightemperatures and drought. C4 metabolism is, however, not free, meaning that underconditions of lower temperature and higher CO2-levels, C3 photosynthesis is still moreviable. This makes it interesting to study how C4-species might shift their ranges in responseto climate change, as it implies both elevated CO 2 levels and higher mean temperatures inmost parts of the world. In this report, I develop a model based on the CO 2/O2 specificity of Rubisco from Spinach(Spinacia oleracea) at different temperatures, using data found in literature on the subject.The resulting model has some success in describing the current distribution of C4 species,using temperature and CO2 concentration as explanatory variables.