title: Predicting stomatal responses to the environment from the optimization of photosynthetic gain and hydraulic cost.
abstract: Stomatal regulation presumably evolved to optimize CO2for H2O exchange in response to changing conditions. If the optimization criterion can be readily measured or calculated, then stomatal responses can be efficiently modelled without recourse to empirical models or underlying mechanism. Previous efforts have been challenged by the lack of a transparent index for the cost of losing water. Yet it is accepted that stomata control water loss to avoid excessive loss of hydraulic conductance from cavitation and soil drying. Proximity to hydraulic failure and desiccation can represent the cost of water loss. If at any given instant, the stomatal aperture adjusts to maximize the instantaneous difference between photosynthetic gain and hydraulic cost, then a model can predict the trajectory of stomatal responses to changes in environment across time. Results of this optimization model are consistent with the widely used Ball-Berry-Leuning empirical model (r2> 0.99) across a wide range of vapour pressure deficits and ambient CO2concentrations for wet soil. The advantage of the optimization approach is the absence of empirical coefficients, applicability to dry as well as wet soil and prediction of plant hydraulic status along with gas exchange.
authors.affiliation: Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Sperry
authors.affiliation: Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Venturas
authors.affiliation: Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA.
authors.forename: William R L
authors.initials: WRL
authors.lastname: Anderegg
authors.affiliation: School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3Ju, UK.|ICREA at CREAF, Cerdanyola del Vallès, Barcelona, 08193, Spain.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mencuccini
authors.affiliation: Department of Geography, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: D Scott
authors.initials: DS
authors.lastname: Mackay
authors.affiliation: Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA.
authors.forename: Yujie
authors.identifier: http://orcid.org/0000-0002-3729-2743
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Love
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D008027:Light; D008954:Models, Biological; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology*; D012987:Soil / Q000737:chemistry; D013696:Temperature; D014867:Water
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide
keywords: Ball-Berry-Leuning model; Cowan-Farquhar optimization; hydraulic limitations; photosynthetic optimization; plant drought responses; plant gas exchange; stomatal modelling; stomatal regulation; xylem cavitation