Desert dogma revisited: coupling of stomatal conductance and photosynthesis in the desert shrub, <i>Larrea tridentata</i>

TitleDesert dogma revisited: coupling of stomatal conductance and photosynthesis in the desert shrub, Larrea tridentata
Publication TypeJournal Article
Year of Publication2002
AuthorsOgle K., Reynolds J.F
JournalPlant, Cell and Environment
Volume25
Pagination909-921
Date Published2002
Call Number00791
Keywordsarticle, articles, journal, journals, Larrea, evapotranspiration, Larrea, photosynthesis, Larrea, transpiration, Larrea,gas-exchange, model, A-Season, model, Ball-Berry, model, Larrea, model, Leuning, model, Pitman, photosynthesis, Larrea, physiology, Larrea
AbstractThe 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 modeling 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 (Øpd), 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 (Ci) and g. Vapor pressure deficit (VPD) and Øpd affect instantaneous g in a manner that is consistent with a biophysical model of stomatal regulation of leaf water potential. Ci is modeled as a function of g, derived from a simplification of a typical A-Ci curve. After incorporating the effects of growing temperature on stomatal behavior, the model was able to capture the large diurnal fluctuations in A, g and Ci and the observed hysteresis in g versus Ci 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 Øpd but not for mechanisms of temperature acclimation and CO2 demand.
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