Document: VIN-3-30-1

Combining the Ball-Berry and ABA models of stomatal control: Experiments, computational models, and some implications for mechanisms.

GUTSCHICK, V.P.* ¹, F.TARDIEU ² and T.SIMONNEAU ²

New Mexico State University, Las Cruces, NM, USA ¹
ENSA M- INRA, Montpellier, Herault, France ²

Abstract:
Two models for predicting stomatal conductance are well-tested, simply parametrized, and widely used: the Ball-Berry model for responses to the aerial environment and the water-stress (ABA) model of Tardieu and co-workers. The combined response has not been tested with resolution both of aerial variables and of ABA. We analyze stomatal conductance (g_s) of sunflower measured by gas exchange in terms of (1) the Ball-Berry index, I_BB = A h_s/C_s, with A=assimilation and h_s, C_s = humidity, CO₂ at leaf surface, composed with additional micrometeorological measurements and (2) [ABA] in xylem sap. A robust fit is g_s = I_BB*exp(-*[ABA]). An alternative model, g_s=min(m*I_BB, g_s,maxexp(-*[ABA])+b, fits less well. In the first, or multiplicative model, further statistical analyses reveal a multiplication of the direct ABA effect by positive feedbacks in the Ball-Berry response. An heuristic model of the mechanism, in which ABA changes the sensitivity of g_s to internal CO₂ signals, simulates the data well. The predictive power of the multiplicative model is sufficiently high for use in estimating fluxes from leaf to region, including effects of soil texture and rooting patterns.

Keywords: stomata, conductance, Ball-Berry, ABA

This abstract is being presented at: 10:30 AM in session:
GAS EXCHANGE