An overview of models of stomatal conductance at the leaf level

Abstract

Stomata play a key role in plant adaptation to changing environmental conditions as they control both water losses and CO2 uptake. Particularly, in the context of global change, simulations of the consequences of drought on crop plants are needed to design more efficient and water-saving cropping systems. However, most of the models of stomatal conductance (gs) developed at the leaf level link gs to environmental factors or net photosynthesis (Anet), but do not include satisfactorily the effects of drought, impairing our capacity to simulate plant functioning in conditions of limited water supply. The objective of this review was to draw an up-to-date picture of the gs models, from the empirical to the process-based ones, along with their mechanistic or deterministic bases. It focuses on models capable to account for multiple environmental influences with emphasis on drought conditions. We examine how models that have been proposed for well-watered conditions can be combined with those specifically designed to deal with drought conditions. Ideas for future improvements of gs models are discussed: the issue of co-regulation of gs and Anet; the roles of CO2, absissic acid and H2O2; and finally, how to better address the new challenges arising from the issue of global change.

Stomatal Function across Temporal and Spatial Scales: Deep-Time Trends, Land-Atmosphere Coupling and Global Models

“…Stomatal control of leaf gas exchange was formulated in terms of optimization theory almost four decades ago (Cowan and Farquhar, 1977), but stomatal control has been modeled predominantly using semiempirical or hybrid mechanisticempirical approaches (Damour et al, 2010). One difficulty with the practical application of optimization theory is quantifying the ratio of sensitivities of the rates of transpiration (E) and CO 2 assimilation (A) to changes in stomatal conductance to water vapor (g w ), defined as the gain ratio (∂E/∂g w )/(∂A/∂g w ), or simply ∂E/∂A (Farquhar et al, 1980a).…”

“…Other models impose biochemical limitations and indirectly reduce stomatal conductance by reducing A as soil moisture stress increases (the models explicitly scale g w with A; otherwise, water-use efficiency would decrease rather than increase with increased biochemical limitation on A). Neither approach can entirely replicate observations (Damour et al, 2010;Egea et al, 2011;De Kauwe et al, 2013), and possibly both diffusive and biochemical limitations must be considered (Zhou et al, 2013). There is also uncertainty about the form of the soil moisture stress function (Verhoef and Egea, 2014).…”

Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model

“…In the absence of further experimental data for Arabidopsis with which to parametrize complex and speculative models, we choose a simple conductance function that captures the effect of varying total open stomatal area. The key observation that stomatal opening (and hence conductance) is reduced in low water supply conditions with respect to well-watered conditions [36,37,40] is thus modelled here by including factors of liquid saturation s and stomatal density l into our conductance function. A simple such representation of the water conductance incorporates linear dependence on s and l, and our final transpiration rate is given by…”

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

“…The imbalance between the rates of water demand in the leaf and water supply from the soil imposes hydrodynamic limitations on stomatal conductance [Bohrer et al, 2005;Damour et al, 2010;McCulloh and Sperry, 2005;Tyree and Sperry, 1989]. Hydraulic limitations have recently been linked to the hysteretic relationship between transpiration (or stomatal conductance) and vapor pressure deficit (VPD) Novick et al, 2014;O'Brien et al, 2004;Unsworth et al, 2004;Verbeeck et al, 2007a;Zhang et al, 2014].…”