Oxygen isotope fractionations across individual leaf carbohydrates in grass and tree species

Plant Cell Environ. 2017 Aug;40(8):1658-1670. doi: 10.1111/pce.12974. Epub 2017 Jun 2.


Almost no δ18 O data are available for leaf carbohydrates, leaving a gap in the understanding of the δ18 O relationship between leaf water and cellulose. We measured δ18 O values of bulk leaf water (δ18 OLW ) and individual leaf carbohydrates (e.g. fructose, glucose and sucrose) in grass and tree species and δ18 O of leaf cellulose in grasses. The grasses were grown under two relative humidity (rH) conditions. Sucrose was generally 18 O-enriched compared with hexoses across all species with an apparent biosynthetic fractionation factor (εbio ) of more than 27‰ relative to δ18 OLW , which might be explained by isotopic leaf water and sucrose synthesis gradients. δ18 OLW and δ18 O values of carbohydrates and cellulose in grasses were strongly related, indicating that the leaf water signal in carbohydrates was transferred to cellulose (εbio = 25.1‰). Interestingly, damping factor pex px , which reflects oxygen isotope exchange with less enriched water during cellulose synthesis, responded to rH conditions if modelled from δ18 OLW but not if modelled directly from δ18 O of individual carbohydrates. We conclude that δ18 OLW is not always a good substitute for δ18 O of synthesis water due to isotopic leaf water gradients. Thus, compound-specific δ18 O analyses of individual carbohydrates are helpful to better constrain (post-)photosynthetic isotope fractionation processes in plants.

Keywords: invertase; isomerization; non-structural carbohydrates (NSC); phosphoglucose isomerase; sucrose synthase; sugars; trioses.

MeSH terms

  • Carbohydrates / analysis*
  • Cellulose / metabolism
  • Chemical Fractionation
  • Humidity
  • Linear Models
  • Oxygen Isotopes / metabolism*
  • Plant Leaves / metabolism*
  • Poaceae / metabolism*
  • Species Specificity
  • Sucrose / metabolism
  • Trees / metabolism*
  • Water


  • Carbohydrates
  • Oxygen Isotopes
  • Water
  • Sucrose
  • Cellulose