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Effects of Elevated CO2 on Spring Wheat
Garcia, R.L., Long, S.P., Wall, G.W., Osborne, C.P., Kimball, B.A., Nie, G.Y., Pinter Jr., P.J., LaMorte, R.L. and Wechsung, F.  1998.  Photosynthesis and conductance of spring-wheat leaves: field response to continuous free-air atmospheric CO2 enrichment.  Plant, Cell and Environment 21: 659-669.

What was done
Spring wheat was grown in the field near Maricopa, Arizona, USA, from emergence to maturity in FACE plots receiving 370 and 550 ppm CO2 to determine the effects of elevated CO2 on photosynthesis and stomatal conductance.

What was learned
In these field plots, where soil nutrition was good and rooting volume was not limiting, elevated CO2 enhanced the average midday rate of photosynthesis by 28% over control plants during the course of the growing season.  In addition, atmospheric CO2 enrichment reduced rates of midday stomatal conductance by 36% relative to rates measured in plants grown at ambient CO2.  Thus, the water-use efficiency of the CO2-enriched plants was enhanced by about a third on a whole crop basis.

What it means
This study demonstrates that the photosynthetic stimulation induced by atmospheric CO2 enrichment persists throughout the growing season in field-grown spring wheat without showing signs of acclimation.  Thus, as the air's CO2 content continues to rise, spring wheat cultivars will likely increase their rates of photosynthesis.  In addition, with likely decreases in stomatal conductance, more carbohydrates can be synthesized with less water loss, thereby raising plant water-use efficiency.  This phenomenon could help protect spring wheat yields in areas where water stress may occur.

Reviewed 15 June 1999