EGU24-12841, updated on 09 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Photosynthesis results in 2H-depleted carbohydrates, but why?

Roland A. Werner1 and Meisha Holloway-Phillips2
Roland A. Werner and Meisha Holloway-Phillips
  • 1ETH Zurich, Department of Environmental Systems Science, Zurich, Switzerland (
  • 2WSL Birmensdorf, Birmensdorf, Switzerland (

When you grow plants in the light, the hydrogen isotopic composition (δ2H) of plant compounds such as cellulose show lower δ2H values (are 2H-depleted) relative to plants grown heterotrophically in the dark. Therefore, it is logical to assume that photosynthetic reactions introduce 2H-depleted hydrogen atoms into carbohydrates. But where in the C reductive pathway (Calvin-Benson-Bassham cycle, CBB) does this occur? Or more interestingly, can we interpret the degree of 2H-depletion of plant compounds with respect to this key reaction(s)? With the recent resurgence of studies offering hydrogen isotopes as a new proxy for plant central carbon and energy metabolism, such a fundamental question seems pertinent to answer.

We 1) examine the stereospecific mechanism of hydride transfer via NADP(H) catalyzed by oxidoreductases (ferredoxin-NADP+ reductase, glyceraldehyde 3-phosphate dehydrogenase) as a key reason why photoproduced NADPH is not directly the source of 2H-depletion of autotrophically produced carbohydrates, 2) reconcile the site-specific deuterium abundance pattern differences between C3 and C4 (NADP-ME) species of hydrogen bound to position C-4 in glucose, and 3) urge greater investment in position-specific and complimentary metabolomic analyses to progress the development of hydrogen isotopes as a metabolic proxy.

How to cite: Werner, R. A. and Holloway-Phillips, M.: Photosynthesis results in 2H-depleted carbohydrates, but why?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12841,, 2024.