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Elevated CO2 Alleviates Drought Stress in Wheat
Wall, G.W.  2001.  Elevated atmospheric CO2 alleviates drought stress in wheat.  Agriculture, Ecosystems and Environment 87: 261-271.

What was done
Spring wheat (Triticum aestivum L. cv. Yecora Roja) was grown in a FACE experiment located near Phoenix, Arizona, USA.  Plants were grown in 25-m diameter plots that received atmospheric CO2 concentrations of 370 and 550 ppm.  In addition, half of the plants were subjected to a well-watered irrigation regime, while the other half received only 50% as much irrigation water (water-stressed regime).  In this paper, therefore, the author reports the effects of elevated CO2 and water stress on this important cereal crop.

What was learned
As the amount of moisture in the soil decreased, leaf water potentials of CO2-enriched plants were always higher (less negative) than those of ambiently-grown plants, due to CO2-induced improvements in both drought avoidance and drought tolerance.  In fact, during the driest part of this two-year study, CO2-enriched plants in the "dry" irrigation treatment exhibited leaf water potentials that were similar in value to those measured on ambiently-grown plants in the "wet" irrigation treatment.  Thus, elevated CO2 completely ameliorated the effects of water-stress in these plants, as inferred by leaf water potential data.

What it means
As the atmospheric CO2 concentration increases, wheat plants will likely fare better under drought conditions than they presently do for several different reasons.  First, CO2-induced reductions in stomatal conductance should reduce transpirational water loss, so that soil water uptake per unit leaf area will likely be decreased while still maintaining a favorable plant water status.  Second, enhanced rates of photosynthesis should allow greater partitioning of carbohydrates belowground, thereby enhancing root growth and enabling plants to better explore the soil for precious water supplies during times of drought.

Reviewed 2 January 2002