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Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2

Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2
Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2
Using a free-air CO2 enrichment (FACE) experiment, poplar trees (Populus x euramericana clone 1214) were exposed to either ambient or elevated [CO2] from planting, for a 5-year period during canopy development, closure, coppice and re-growth. In each year, measurements were taken of stomatal density (SD, number mm(-2)) and stomatal index (SI, the proportion of epidermal cells forming stomata). In year 5, measurements were also taken of leaf stomatal conductance (g(s) mu mol m(-2) s(-1)), photosynthetic CO2 fixation (A, mmol m(-2) s(-1)), instantaneous water-use efficiency (A/E) and the ratio of intercellular to atmospheric CO2 (C-i:C-a). Elevated [CO2] caused reductions in SI in the first year, and in SD in the first 2 years, when the canopy was largely open. In following years, when the canopy had closed, elevated [CO2] had no detectable effects on stomatal numbers or index. In contrast, even after 5 years of exposure to elevated [CO2], g(s) was reduced, A/E was stimulated, and C-i:C-a was reduced relative to ambient [CO2]. These outcomes from the long-term realistic field conditions of this forest FACE experiment suggest that stomatal numbers (SD and SI) had no role in determining the improved instantaneous leaf-level efficiency of water use under elevated [CO2]. We propose that altered cuticular development during canopy closure may partially explain the changing response of stomata to elevated [CO2], although the mechanism for this remains obscure.
populus × euramericana, stomatal numbers, stomatal conductance, popface
0029-8549
652-660
Tricker, Penny J.
a4db1985-2cd5-4356-b932-77ae8ed7d25c
Trewin, Harriet
ca9a9ee7-dd07-4c57-8aa1-5fb4ec3cbbdc
Kull, Olevi
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Clarkson, Graham J.J.
ef06b7b4-509b-4ebe-9327-c8950c4f44b3
Eensalu, Eve
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Tallis, Matthew J.
25cbd143-1f8c-491b-9eac-f1c632dfcfda
Colella, Alessio
8e60f81b-2f6a-4aca-b665-492f02140d35
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047
Sabatti, Maurizio
1af6616e-e66f-44c0-b783-bb355468a619
Taylor, Gail
f3851db9-d37c-4c36-8663-e5c2cb03e171
Tricker, Penny J.
a4db1985-2cd5-4356-b932-77ae8ed7d25c
Trewin, Harriet
ca9a9ee7-dd07-4c57-8aa1-5fb4ec3cbbdc
Kull, Olevi
6c0e061c-62a3-482b-92f5-e22ab66dafdc
Clarkson, Graham J.J.
ef06b7b4-509b-4ebe-9327-c8950c4f44b3
Eensalu, Eve
88b21a61-dd17-4ed4-98b8-e9c4f7f93e9c
Tallis, Matthew J.
25cbd143-1f8c-491b-9eac-f1c632dfcfda
Colella, Alessio
8e60f81b-2f6a-4aca-b665-492f02140d35
Doncaster, C. Patrick
0eff2f42-fa0a-4e35-b6ac-475ad3482047
Sabatti, Maurizio
1af6616e-e66f-44c0-b783-bb355468a619
Taylor, Gail
f3851db9-d37c-4c36-8663-e5c2cb03e171

Tricker, Penny J., Trewin, Harriet, Kull, Olevi, Clarkson, Graham J.J., Eensalu, Eve, Tallis, Matthew J., Colella, Alessio, Doncaster, C. Patrick, Sabatti, Maurizio and Taylor, Gail (2005) Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2. Oecologia, 143 (4), 652-660. (doi:10.1007/s00442-005-0025-4).

Record type: Article

Abstract

Using a free-air CO2 enrichment (FACE) experiment, poplar trees (Populus x euramericana clone 1214) were exposed to either ambient or elevated [CO2] from planting, for a 5-year period during canopy development, closure, coppice and re-growth. In each year, measurements were taken of stomatal density (SD, number mm(-2)) and stomatal index (SI, the proportion of epidermal cells forming stomata). In year 5, measurements were also taken of leaf stomatal conductance (g(s) mu mol m(-2) s(-1)), photosynthetic CO2 fixation (A, mmol m(-2) s(-1)), instantaneous water-use efficiency (A/E) and the ratio of intercellular to atmospheric CO2 (C-i:C-a). Elevated [CO2] caused reductions in SI in the first year, and in SD in the first 2 years, when the canopy was largely open. In following years, when the canopy had closed, elevated [CO2] had no detectable effects on stomatal numbers or index. In contrast, even after 5 years of exposure to elevated [CO2], g(s) was reduced, A/E was stimulated, and C-i:C-a was reduced relative to ambient [CO2]. These outcomes from the long-term realistic field conditions of this forest FACE experiment suggest that stomatal numbers (SD and SI) had no role in determining the improved instantaneous leaf-level efficiency of water use under elevated [CO2]. We propose that altered cuticular development during canopy closure may partially explain the changing response of stomata to elevated [CO2], although the mechanism for this remains obscure.

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Published date: May 2005
Keywords: populus × euramericana, stomatal numbers, stomatal conductance, popface

Identifiers

Local EPrints ID: 41065
URI: https://eprints.soton.ac.uk/id/eprint/41065
ISSN: 0029-8549
PURE UUID: bc774a5e-96f2-49fc-9c39-3ce50db95b7c
ORCID for C. Patrick Doncaster: ORCID iD orcid.org/0000-0001-9406-0693

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Date deposited: 14 Jul 2006
Last modified: 06 Jun 2018 13:04

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Contributors

Author: Penny J. Tricker
Author: Harriet Trewin
Author: Olevi Kull
Author: Graham J.J. Clarkson
Author: Eve Eensalu
Author: Matthew J. Tallis
Author: Alessio Colella
Author: Maurizio Sabatti
Author: Gail Taylor

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