The influence of N metabolism and organic acid synthesis on the natural abundance of isotopes of carbon in plants

摘要: SUMMARY This paper relates the 13C/12C ratio of C3 plant material relative to that source CO2 N for growth, organic content plant, and extent acid synthesis. The is quantified as Δ, defined (δ13C substrate –δ13C product)/(1+δ13C product), where δ13C values or product (i.e. samples) are [13C/12C]sample]/[(13C/12C)standard]−1. computation performed by relating differences in composition a function nutrition synthesis fraction C which acquired via Rubisco other carboxylases. fractional contribution different carboxylases gain then related, using known isotopic fractionations exhibited these carboxylases, model predict final Δ (relative atmospheric CO2). Application this approach ‘typical’ land yields predictions decrease hypothetical case all fixed Rubisco. predicted decreases range from 0–24 %, NH4+ assimilation (which always occurs roots) 2–80%, NO3− shoots with salt results acid-base balance, plus any additional salts free acids basal C:N molar 15. Intermediate symbiotic growth N2, root shoot accompanied some regulation OH- loss medium. Comparison published data on difference Ricinus communis cultured shows measured influence nitrogen right direction (NO3− grown plants smaller i.e. larger deviation value absence non-Rubisco carboxylations) be explained observed hence various However, effect greater than model, 2.1 % opposed 0.10 decrease. It likely major cause two sources change transport biochemical conductances leaf photosynthesis. Such quantitatively consistent lower water use efficiency -grown plants. The predicted, observed, changes same magnitude those found terrestrial species at temperatures photon flux densities, environments yielding efficiencies changing supply evaporation potential. Variations should added factors might alter δ growing field.