Preprint Brief Report Version 2 Preserved in Portico This version is not peer-reviewed

Increased Respiration by the Oxidative Pentose Phosphate Pathway in Chloroplasts at High Atmospheric CO2 Concentration

Version 1 : Received: 4 March 2022 / Approved: 7 March 2022 / Online: 7 March 2022 (14:50:43 CET)
Version 2 : Received: 22 April 2022 / Approved: 26 April 2022 / Online: 26 April 2022 (09:49:53 CEST)
Version 3 : Received: 13 May 2022 / Approved: 16 May 2022 / Online: 16 May 2022 (12:14:30 CEST)

How to cite: Wieloch, T. Increased Respiration by the Oxidative Pentose Phosphate Pathway in Chloroplasts at High Atmospheric CO2 Concentration. Preprints 2022, 2022030104 (doi: 10.20944/preprints202203.0104.v2). Wieloch, T. Increased Respiration by the Oxidative Pentose Phosphate Pathway in Chloroplasts at High Atmospheric CO2 Concentration. Preprints 2022, 2022030104 (doi: 10.20944/preprints202203.0104.v2).

Abstract

Despite significant research efforts, the question of whether rising atmospheric CO2 concentrations (Ca) affect leaf respiration remains unanswered. Here, I reanalyse published hydrogen isotope abundances in starch glucose of sunflower leaves. I report that, as Ca increases from 450 to 1500 ppm, respiration by the oxidative pentose phosphate pathway in chloroplasts increases from 0 to ≈ 5% relative to net carbon assimilation. This is consistent with known regulatory properties of the pathway. Summarising recent reports of metabolic fluxes in plant leaves, a picture emerges in which mitochondrial processes are distinctly less important for overall respiration than the oxidative pentose phosphate pathways in chloroplasts and the cytosol. Regulatory properties of these pathways are consistent with observations of lower-than-expected stimulations of photosynthesis by increasing Ca. Reported advances in understanding leaf respiratory mechanisms may enable modelling and prediction of respiration effects (inter alia) on biosphere-atmosphere CO2 exchange and plant performance under climate change.

Keywords

Calvin-Benson cycle; carbon metabolism; CO2 fertilisation; glucose-6-phosphate shunt; hydrogen stable isotopes; oxidative pentose phosphate pathway; photosynthesis; respiration

Subject

BIOLOGY, Plant Sciences

Comments (1)

Comment 1
Received: 26 April 2022
Commenter: Thomas Wieloch
Commenter's Conflict of Interests: Author
Comment: - changed title
- revised paragraph: "Potential causes of lower-than-expected increases of photosynthesis due to increasing Ca"
- added Figure 2
- added Supporting information
- numerous minor changes throughout the manuscript
+ Respond to this comment

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