Stomatal control of xylem embolism

Abstract

Abstract. The potential role of stomatal closure in the control of xylem embolism is investigated by means of a simple model of hydraulic flow in plants. Maintenance of a maximally efficient conducting system requires the stomata to close in an appropriate fashion as evaporative demand increases in order to prevent shoot water potentials falling below the threshold value at which cavitations occur. The model showed that the optimal stomatal behaviour required depends on soil water availability. Further analysis of the model demonstrated that there could be certain circumstances where loss of a proportion of the conducting tissue by embolisms can, perhaps surprisingly, be beneficial in terms of maximizing stomatal aperture and hence short‐term productivity. The results are discussed in relation to the signals controlling stomatal aperture, and it is shown that (1) optimal control cannot be obtained using information on leaf water potential alone, and (2) information relating to soil water potential is a necessary requirement for optimal control.

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

“…It has been proposed that the homeostatic value of y f,min in isohydric woody species lies close to the threshold potential for catastrophic xylem failure due to runaway cavitation (Tyree & Sperry 1988), reflecting an optimization strategy of maximum leaf gas exchange that would involve some loss of xylem conductivity (Jones & Sutherland 1991). In their modelling study, Jones & Sutherland (1991) also examined a second possibility, that y f,min coincides with the onset of xylem embolism, reflecting a more conservative (cavitation-avoidance) strategy.…”

“…In their modelling study, Jones & Sutherland (1991) also examined a second possibility, that y f,min coincides with the onset of xylem embolism, reflecting a more conservative (cavitation-avoidance) strategy.…”

“…2a shows, the water supply curve (J w versus y e ) falls to zero at y e = y s (zero soil-to-leaf water potential gradient) and y e = y xL (complete loss of hydraulic conductivity through xylem embolism). The intermediate point at which J w has a maximum represents the water potential below which catastrophic xylem failure through runaway cavitation would occur in the absence of stomatal regulation of y e (Tyree & Sperry 1988;Jones & Sutherland 1991).…”

“…aim 4). Following Jones & Sutherland (1991), a simple ramp function is used to describe the relationship between the xylem hydraulic conductivity L re = 1/R re and leaf epidermal water potential (cf. Eqn 4b): in which L max is the maximum root-to-leaf hydraulic conductivity, y tL is the threshold potential at which L re starts to decline and y xL is the value of y e at which L re falls to zero.…”

Diurnal and seasonal variation in root xylem embolism in neotropical savanna woody species: impact on stomatal control of plant water status

“…It is possible that this narrow safety margin for disruption of water movement might serve to buffer leaf water status by inducing early stomatal closure (Jones & Sutherland 1991). A recent study suggests that in conifers, embolism in roots may be involved in stomatal regulation of seasonal minimum water potentials (Domec et al .…”