HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Grant, R. F. Search for Related Content PubMed Articles by Grant, R. F. Agricola Articles by Grant, R. F.

Interactions between Carbon Dioxide and Water Deficits Affecting Canopy Photosynthesis: Simulation and Testing

Dep. of Soil Science, Univ. of Alberta, Edmonton, Alberta T6G 2E3

^* Corresponding author.

Increases in atmospheric CO₂ concentrations (C_a) are likely to increase CO₂ fixation and reduce transpiration by crop canopies. Mathematical modeling of the processes controlling gas exchange may be used to estimate the extent to which exchange is likely to be altered by C_a under site-specific conditions. A simulation model was constructed from fundamental equations for CO₂ fixation, transpiration and energy exchange in order to estimate canopy gas exchange under different C_a. The model was then tested with data from a growth chamber study. The model reproduced an increase in net photosynthesis from 35 to 65 µmol m^–2 s^–1, and a decrease in transpiration from 14 000 to 11 000 µmol m^–2 s^–1, for an irrigated soybean [Glycine max (L.) Merr.] canopy when C_a was increased from 330 to 800 µmol mol^–1. The consequent increase in water use efficiency from 2.7 to .5 mmol mol^–1 was confirmed from the growth chamber study. In the model, this increase was governed by changes in the partitioning of latent and sensible components of the crop energy balance arising from changes in canopy stomatal resistance. Changes in the ratios of latent and sensible heat fluxes simulated by the model at C_a = 800 vs. 330 µmol mol^–1 caused simulated increases in canopy temperatures of 1.0 °C, similar to recorded increases in other studies. There is evidence from model output that changes in canopy CO₂ fixation caused by C_a may be reduced in water stressed canopies. However, our understanding of water deficit effects on photosynthesis remains largely empirical, so that estimates of canopy gas exchange under combined water deficits and changed C_a remain speculative. There is a need to extend experimental studies of C_a effects on photosynthesis and transpiration to include studies under water stress in order to test model hypotheses.

Received for publication July 8, 1991.

This article has been cited by other articles:

				R.F. Grant, N.G. Juma, J.A. Robertson, R.C. Izaurralde, and W.B. McGill Long-Term Changes in Soil Carbon under Different Fertilizer, Manure, and Rotation: Testing the Mathematical Model ecosys with Data from the Breton Plots Soil Sci. Soc. Am. J., January 1, 2001; 65(1): 205 - 214. [Abstract] [Full Text]