Optimal Stomatal Theory Predicts Co₂ Responses of Stomatal Conductance in Both Gymnosperm and Angiosperm Trees

Gardner, Anna
Jiang, Mingkai
Ellsworth, David
MacKenzie, A Rob
Pritchard, Jeremy
Bader, Martin Karl-Friedrich
Barton, Craig
Bernacchi, Carl
Calfapietra, Carlo
Crous, Kristine Y
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Optimal stomatal theory predicts that stomata operate to maximize photosynthesis (Anet ) and minimize 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 plant functional types (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 to 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 to angiosperm, species.

Land surface models can use the USO model to describe stomatal behaviour under changing atmospheric CO2 conditions.

climate change , deciduous , evergreen , Free-air CO2 enrichment , photosynthesis , water use efficiency , climate change , deciduous , evergreen , free-air CO2 enrichment , photosynthesis , water-use efficiency , 3108 Plant Biology , 31 Biological Sciences , 06 Biological Sciences , 07 Agricultural and Veterinary Sciences , Plant Biology & Botany , 3108 Plant biology , 4101 Climate change impacts and adaptation , 4102 Ecological applications
New Phytologist, ISSN: 0028-646X (Print); 1469-8137 (Online), Wiley, 237(4), 1229-1241. doi: 10.1111/nph.18618
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