The Ball–Berry–Leuning and Tardieu–Davies stomatal models: synthesis and extension within a spatially aggregated picture of guard cell function

Abstract

A new model of stomatal conductance is proposed which combines the essential features of the Ball-Berry-Leuning (BBL) and Tardieu-Davies (TD) models within a simple spatially aggregated picture of guard cell function. The model thus provides a coherent description of stomatal responses to both air and soil environments. The model also presents some novel features not included in either the BBL or TD models: stomatal sensing of intercellular (rather than leaf surface) CO 2 concentration; an explanation of all three observed regimes (A, B and C) of the stomatal response to air humidity (Monteith Plant, Cell and Environment 18, 357-364, 1995); incorporation of xylem embolism; and maintenance of hydraulic homeostasis by combined hydraulic and chemical signalling in leaves (in which leaf epidermal hydraulic conductivity plays a key role). Significantly, maintenance of hydraulic homeostasis in the model does not require a direct feedback signal from xylem embolism, the predicted minimum leaf water potential being independent of xylem hydraulic conductivity. It is suggested that stomatal regulation through combined hydraulic and chemical signalling in leaves and/or roots provides a general mechanism enabling plants to maintain their water potentials above a minimum value. Natural selection of the key stomatal parameters would then set the minimum potential to a specific value determined by the most vulnerable plant process under water stress (e.g. cell growth, protein synthesis or xylem cavitation), depending on species and growth conditions.

Reduced plant water status under sub-ambientpCO2limits plant productivity in the wild progenitors of C3and C4cereals

“…Models of stomatal function consider the hydration of epidermal cells an important control mechanism (e.g. Dewar, 2002;Gao et al, 2002;Buckley et al, 2003), and more recently Peak and Mott (2011 …”

The Sites of Evaporation within Leaves

“…Similarly, preferential evaporation from guard cells in dry air could explain the stomatal response to humidity by causing a larger turgor decline in guard cells than in epidermal cells, overcoming the epidermal mechanical advantage (Maier-Maercker, 1983;Sheriff, 1984;Dewar, 1995Dewar, , 2002. Several previous authors have attempted to identify the sites of evaporation using experimental and/or modeling approaches.…”

Stomatal Response to Humidity: Blurring the Boundary between Active and Passive Movement

“…OnGuard is a proven computational platform for modeling stomatal physiology that encompasses guard cell transport, signaling, and homeostasis, and has predicted stomatal behavior across species (Chen et al, 2012;Wang et al, 2012). In OnGuard2, Wang et al (2017) connect these processes, largely ignored in past models of g s (Dewar, 2002;Peak and Mott, 2011), with water in the guard cell wall. They allow the wall to equilibrate with the water vapor pressure in the substomatal cavity adjacent to the guard cells.…”