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

Authors: LEAKEY, ANDREW D - UNIVERSITY OF ILLINOS; BERNACCHI, CARL - ILLINOIS STATE WATER SURB; Ort, Donald; LONG, STEPHEN - UNIVERSITY OF ILLINOIS

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2006
Publication Date: 10/10/2006
Citation: Leakey, A.B., Bernacchi, C., Ort, D.R., Long, S.L. 2006. Long-term growth of soybean at elevated [CO2] does not cause acclimation of stomatal conductance under fully open-air conditions. American Society of Plant Biologists Annual Meeting. Available at http://www.aspb.org/meetings/transpiration06/justabstracts.cfm.

Interpretive Summary:

Technical Abstract: Accurately predicting plant function and global biogeochemical cycles later 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 micromol mol-1) and elevated [CO2] (552 micromol 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 stomatal conductance independent of photosynthetic acclimation. The Ball et al. (1987) 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 modeled without the need for parameterization at each growth [CO2].