|Leakey, Andrew D.|
Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2006
Publication Date: 6/1/2006
Citation: Leakey, A.B., Bernacchi, C.J., Ort, D.R., Long, S.P. 2006. Growth of soybean under free-air [CO2]enrichment (FACE) does not cause stomatal acclimation. Plant Cell and Environment. 29:1794-1800. Interpretive Summary: Carbon dioxide in the world's atmosphere is on the rise. In the last century it has risen 20% and this geologically unprecedented pace will continue resulting in an atmosphere in 2050 containing 50% more CO2 than it did in 1900. While this enrichment of the atmosphere CO2 promises the potential of increase crop yield, plants do not always sustain the initial response shown to CO2 enrichment. In some cases photosynthesis is known to down regulate and there has been considerable speculation about the long term response of leaf stomata to growth at elevated CO2. Our results show that in the case of soybean, and probably other annual row crops, the direct response of stomates to elevated CO2 is sustained through the entire season. This outcome is important to work aimed at accurately modeling the effects of future atmospheres on crop growth and water use.
Technical Abstract: Accurately predicting plant function later this century will be complicated if stomatal conductance (gs) acclimates to growth at elevated [CO2]. 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 in the crop by parameterizing and validating the 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 ca 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 decreased conductance in response to elevated [CO2] and that there is no independent acclimation of stomatal conductance. The Ball et al. model accurately predicted stomatal conductance 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] can be modeled without the need for parameterization at each growth [CO2].