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The success of the desert shrub Larrea tridentata (creosotebush) has been largely attributed to temperature acclimation and stomatal control of photosynthesis (A ) under drought stress. However, there is a paucity of field data on these relationships. To address this void, we conducted a joint field and modelling study that encompassed a diverse set of environmental conditions. At a Larrea -dominated site in southern New Mexico we manipulated soil moisture during the growing season over a 2-year period and measured plant pre-dawn water potential (Psi (pd) ), stomatal conductance (g ) and A of individual shrubs. We used these data to develop a semi-mechanistic photosynthesis model (A-Season) that explicitly couples internal CO2 (C (i) ) and g . Vapour pressure deficit (VPD ) and Psi (pd) affect instantaneous g in a manner that is consistent with a biophysical model of stomatal regulation of leaf water potential. C (i) is modelled as a function of g , derived from a simplification of a typical A -C (i) curve. After incorporating the effects of growing temperature on stomatal behaviour, the model was able to capture the large diurnal fluctuations in A , g and C (i) and the observed hysteresis in g versus C (i) dynamics. Our field data and application of the A-Season model suggest that dogma attributed to Larrea ’s success is supported with regard to stomatal responses to VPD and Psi (pd) , but not for mechanisms of temperature acclimation and CO2 demand.