Carbon isotope effects on key reactions in plant metabolism and 13C-patterns in natural compounds
H.‐L. Schmidt, Gerd Gleixner
Abstract
For the development of a general interpretation and theory of isotopic discriminations in a closed system like a plant, besides the involvement of isotope effects, the existence of pools and metabolic fluxes in different directions has to be taken into account. This was expressed by S. Epstein in 1968 by the statement: ‘If the carbon of lipids is light, conservation laws require that some other portion of carbon is heavier. Or stated in another way, a change in isotopic ratios implies the splitting of a population of molecules into two or more classes and streams.’ Entering more into the biochemical reasons for isotopic patterns of secondary products, it is obvious that they are linked to kinetic isotope effects on defined enzymatic reactions. The discrimination of hydrogen isotopes in nature starts with thermodynamic isotope effects on the evaporation and condensation of water and on the transpiration by plants.