Preprints
https://doi.org/10.5194/egusphere-2025-807
https://doi.org/10.5194/egusphere-2025-807
04 Mar 2025
 | 04 Mar 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

Abstract. Although numerous experiments have been dedicated to studying plant response to elevated CO2, almost none crossed the level of 1000 ppm. Plant responses to high CO2 levels importantly inform our understanding of plant physiology in ultra-high CO2 environments, e.g., in Earth history, in the case of unmitigated anthropogenic emissions, and for future colonization of Mars.

Here, we challenged two-year old seedlings of fruit trees grown in soil in a mesocosm, with CO2 levels of 400, 1600 and 6000 ppm, the highest of which is approximately equivalent to that of Mars’ atmosphere. Plant growth, and leaf gas exchange (transpiration, stomatal conductance, and CO2 assimilation) were measured on a weekly basis for 3 consecutive weeks. We hypothesized that elevated CO2 levels will induce a decrease in transpiration, primarily attributed to reduced stomatal conductance. Indeed, leaf transpiration was decreased at 1600 ppm CO2 and remained low at 6000 ppm, concurrent with a 50 % decrease in stomatal conductance. The CO2-induced stomatal closure appears to have saturated between 850 and 1600 ppm CO2. Due to this effect, net assimilation was only mildly changed at 1600 ppm CO2, but significantly increased at 6000 ppm. As a result, water-use efficiency quadrupled at 6000 ppm CO2. Stem height increment did not change significantly across the CO2 treatments.

Taken together, our measurements demonstrated both the potential and limit of CO2-induced stomatal closure, with positive implications for fruit tree growth in ultra-high CO2 environments, as on Earth in the case of unmitigated anthropogenic CO2 emissions and on Mars.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
Share

Journal article(s) based on this preprint

29 Sep 2025
| Highlight paper
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
Biogeosciences, 22, 5069–5079, https://doi.org/10.5194/bg-22-5069-2025,https://doi.org/10.5194/bg-22-5069-2025, 2025
Short summary Co-editor-in-chief
Ben-El Levy, Yedidya Ben-Eliyahu, Yaniv-Brian Grunstein, Itay Halevy, and Tamir Klein

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

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 

Journal article(s) based on this preprint

29 Sep 2025
| Highlight paper
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
Biogeosciences, 22, 5069–5079, https://doi.org/10.5194/bg-22-5069-2025,https://doi.org/10.5194/bg-22-5069-2025, 2025
Short summary Co-editor-in-chief
Ben-El Levy, Yedidya Ben-Eliyahu, Yaniv-Brian Grunstein, Itay Halevy, and Tamir Klein
Ben-El Levy, Yedidya Ben-Eliyahu, Yaniv-Brian Grunstein, Itay Halevy, and Tamir Klein

Viewed

Total article views: 819 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
606 187 26 819 45 14 35
  • HTML: 606
  • PDF: 187
  • XML: 26
  • Total: 819
  • Supplement: 45
  • BibTeX: 14
  • EndNote: 35
Views and downloads (calculated since 04 Mar 2025)
Cumulative views and downloads (calculated since 04 Mar 2025)

Viewed (geographical distribution)

Total article views: 795 (including HTML, PDF, and XML) Thereof 795 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 29 Sep 2025
Download

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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 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 water shortage.
Share