Articles | Volume 22, issue 18
https://doi.org/10.5194/bg-22-5069-2025
https://doi.org/10.5194/bg-22-5069-2025
Research article
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29 Sep 2025
Research article | Highlight paper |  | 29 Sep 2025

Physiological responses to ultra-high CO2 levels in an evergreen tree species

Ben-El Levy, Yedidya Ben-Eliyahu, Yaniv-Brian Grunstein, Itay Halevy, and Tamir Klein

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Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-807', Anju Manandhar, 07 Apr 2025
    • AC1: 'Reply on RC1', Tamir Klein, 13 May 2025
  • RC2: 'Comment on egusphere-2025-807', Anonymous Referee #2, 15 Apr 2025
    • AC2: 'Reply on RC2', Tamir Klein, 13 May 2025
  • RC3: 'Comment on egusphere-2025-807', Anonymous Referee #3, 22 Apr 2025
    • AC3: 'Reply on RC3', Tamir Klein, 13 May 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Reconsider after major revisions (25 May 2025) by Andrew Feldman
AR by Tamir Klein on behalf of the Authors (28 May 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (29 May 2025) by Andrew Feldman
RR by Anonymous Referee #3 (11 Jun 2025)
RR by Anonymous Referee #2 (25 Jun 2025)
ED: Publish subject to minor revisions (review by editor) (29 Jun 2025) by Andrew Feldman
AR by Tamir Klein on behalf of the Authors (06 Jul 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (18 Jul 2025) by Andrew Feldman
AR by Tamir Klein on behalf of the Authors (24 Jul 2025)  Manuscript 
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Co-editor-in-chief
The study provides novel findings about plant strategies under very high CO2 atmospheric conditions, such as on Mars. The authors show a large increase in fruit tree water use efficiency, an indicator for how efficiently plants photosynthesize for a given amount of water supply, when the CO2 concentrations are about an order of magnitude higher than that experienced on Earth. Therefore, these fruit trees potentially can survive and grow with less water in these conditions.
Short summary
As atmospheric CO2 increases globally, plants increase the rate of photosynthesis. Still, leaf–gas exchange can be downregulated by the plant. Here we tested the limits of these plant responses in a fruit tree species under very high CO2 levels relevant to the future Earth and to contemporary Mars. Plant water use decreased at 1600 ppm CO2 and remained low at 6000 ppm. Photosynthesis significantly increased at 6000 ppm. In summary, ultra-high CO2 may partly compensate for limited water availability.
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