Long-term growth of soybean at elevated [CO2] does not cause acclimation of stomatal conductance under fully open-air conditions

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Accurately predicting plant function and global biogeochemical cycles later in this century will be complicated if stomatal conductance (gs) acclimates to growth at elevated [CO2], in the sense of a long-term alteration of the response of gs to [CO2], humidity (h) and/or photosynthetic rate (A). If so, photosynthetic and stomatal models will require parameterization at each growth [CO2] of interest. Photosynthetic acclimation to long-term growth at elevated [CO2] occurs frequently. Acclimation of gs has rarely been examined, even though stomatal density commonly changes with growth [CO2]. Soybean was grown under field conditions at ambient [CO2] (378 μmol mol-1) and elevated [CO2] (552 μmol mol-1) using free-air [CO2] enrichment (FACE). This study tested for stomatal acclimation by parameterizing and validating the widely used Ball et al. model (1987, Progress in Photosynthesis Research, vol IV, 221-224) with measurements of leaf gas exchange. The dependence of gs on A, h and [CO2] at the leaf surface was unaltered by long-term growth at elevated [CO2]. This suggests that the commonly observed decrease in gs under elevated [CO2] is due entirely to the direct instantaneous effect of [CO2] on gs and that there is no longer-term acclimation of gs independent of photosynthetic acclimation. The model accurately predicted gs for soybean growing under ambient and elevated [CO2] in the field. Model parameters under ambient and elevated [CO2] were indistinguishable, demonstrating that stomatal function under ambient and elevated [CO2] could be modelled without the need for parameterization at each growth [CO2].

Original languageEnglish (US)
Pages (from-to)1794-1800
Number of pages7
JournalPlant, Cell and Environment
Issue number9
StatePublished - Sep 2006


  • Climate change
  • FACE
  • Glycine max
  • Model
  • Photosynthesis

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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