12C/13C fractionations in plant primary metabolism

Natural 13 C abundance is now an unavoidable tool to study ecosystem and plant carbon economies. A growing number of studies take advantage of isotopic fractionation between carbon pools or 13 C abundance in respiratory CO 2 to examine the carbon source of respiration, plant biomass production or organic matter sequestration in soils. 12 C/ 13 C isotope effects associated with plant metabolism are thus essential to understand natural isotopic signals. However, isotope effects of enzymes do not influence metabolites separately, but combine to yield a 12 C/ 13 C isotopologue redistribution orchestrated by metabolic flux patterns. In this review, we summarise key metabolic isotope effects and integrate them into the corpus of plant primary carbon metabolism.