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Optimal stomatal theory predicts CO2 responses of stomatal conductance in both gymnosperm and angiosperm trees

Gardner, Anna ; Jiang, Mingkai ; Ellsworth, David S. ; MacKenzie, A. Robert ; Pritchard, Jeremy ; Bader, Martin Karl Friedrich ; Barton, Craig V.M. ; Bernacchi, Carl ; Calfapietra, Carlo and Crous, Kristine Y. , et al. (2023) In New Phytologist 237(4). p.1229-1241
Abstract

Optimal stomatal theory predicts that stomata operate to maximise photosynthesis (Anet) and minimise transpirational water loss to achieve optimal intrinsic water-use efficiency (iWUE). We tested whether this theory can predict stomatal responses to elevated atmospheric CO2 (eCO2), and whether it can capture differences in responsiveness among woody plant functional types (PFTs). We conducted a meta-analysis of tree studies of the effect of eCO2 on iWUE and its components Anet and stomatal conductance (gs). We compared three PFTs, using the unified stomatal optimisation (USO) model to account for confounding effects of leaf–air vapour pressure difference (D). We expected... (More)

Optimal stomatal theory predicts that stomata operate to maximise photosynthesis (Anet) and minimise transpirational water loss to achieve optimal intrinsic water-use efficiency (iWUE). We tested whether this theory can predict stomatal responses to elevated atmospheric CO2 (eCO2), and whether it can capture differences in responsiveness among woody plant functional types (PFTs). We conducted a meta-analysis of tree studies of the effect of eCO2 on iWUE and its components Anet and stomatal conductance (gs). We compared three PFTs, using the unified stomatal optimisation (USO) model to account for confounding effects of leaf–air vapour pressure difference (D). We expected smaller gs, but greater Anet, responses to eCO2 in gymnosperms compared with angiosperm PFTs. We found that iWUE increased in proportion to increasing eCO2 in all PFTs, and that increases in Anet had stronger effects than reductions in gs. The USO model correctly captured stomatal behaviour with eCO2 across most datasets. The chief difference among PFTs was a lower stomatal slope parameter (g1) for the gymnosperm, compared with angiosperm, species. Land surface models can use the USO model to describe stomatal behaviour under changing atmospheric CO2 conditions.

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@article{146c34f5-2284-4e6a-abeb-0fa99921170a,
  abstract     = {{<p>Optimal stomatal theory predicts that stomata operate to maximise photosynthesis (A<sub>net</sub>) and minimise transpirational water loss to achieve optimal intrinsic water-use efficiency (iWUE). We tested whether this theory can predict stomatal responses to elevated atmospheric CO<sub>2</sub> (eCO<sub>2</sub>), and whether it can capture differences in responsiveness among woody plant functional types (PFTs). We conducted a meta-analysis of tree studies of the effect of eCO<sub>2</sub> on iWUE and its components A<sub>net</sub> and stomatal conductance (g<sub>s</sub>). We compared three PFTs, using the unified stomatal optimisation (USO) model to account for confounding effects of leaf–air vapour pressure difference (D). We expected smaller g<sub>s</sub>, but greater A<sub>net</sub>, responses to eCO<sub>2</sub> in gymnosperms compared with angiosperm PFTs. We found that iWUE increased in proportion to increasing eCO<sub>2</sub> in all PFTs, and that increases in A<sub>net</sub> had stronger effects than reductions in g<sub>s</sub>. The USO model correctly captured stomatal behaviour with eCO<sub>2</sub> across most datasets. The chief difference among PFTs was a lower stomatal slope parameter (g<sub>1</sub>) for the gymnosperm, compared with angiosperm, species. Land surface models can use the USO model to describe stomatal behaviour under changing atmospheric CO<sub>2</sub> conditions.</p>}},
  author       = {{Gardner, Anna and Jiang, Mingkai and Ellsworth, David S. and MacKenzie, A. Robert and Pritchard, Jeremy and Bader, Martin Karl Friedrich and Barton, Craig V.M. and Bernacchi, Carl and Calfapietra, Carlo and Crous, Kristine Y. and Dusenge, Mirindi Eric and Gimeno, Teresa E. and Hall, Marianne and Lamba, Shubhangi and Leuzinger, Sebastian and Uddling, Johan and Warren, Jeffrey and Wallin, Göran and Medlyn, Belinda E.}},
  issn         = {{0028-646X}},
  keywords     = {{climate change; deciduous; evergreen; free-air CO enrichment; photosynthesis; water-use efficiency}},
  language     = {{eng}},
  number       = {{4}},
  pages        = {{1229--1241}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{New Phytologist}},
  title        = {{Optimal stomatal theory predicts CO<sub>2</sub> responses of stomatal conductance in both gymnosperm and angiosperm trees}},
  url          = {{http://dx.doi.org/10.1111/nph.18618}},
  doi          = {{10.1111/nph.18618}},
  volume       = {{237}},
  year         = {{2023}},
}