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Effects of Elevated CO2 and Ozone Concentrations on Spring Wheat Grown at Different Levels of Soil Nitrogen Supply
Vilhena-Cardoso, J. and Barnes, J.  2001.  Does nitrogen supply affect the response of wheat (Triticum aestivum cv. Hanno) to the combination of elevated CO2 and O3Journal of Experimental Botany 52: 1901-1911.

What was done
Spring wheat (Triticum aestivum cv. Hanno) was grown for two months in environmental chambers fumigated with air containing atmospheric CO2 concentrations of 350 and 700 ppm at ambient and elevated (75 ppb) ozone concentrations.  In addition, plants were simultaneously subjected to low, medium and high levels of soil nitrogen to see if soil nitrogen supply alters the effects of elevated CO2 and ozone on photosynthesis and biomass production in this important agricultural crop.

What was learned
Plants grown at 700 ppm CO2 displayed significantly higher rates of net photosynthesis than control plants grown in ambient air, regardless of soil nitrogen supply.  In addition, although elevated ozone reduced photosynthetic rates in ambiently-grown plants, it had no effect on CO2-enriched plants, which continued to maintain enhanced photosynthetic rates even in the high ozone treatments.

With respect to biomass production, elevated CO2 increased total plant dry weight by 44, 29 and 12% at high, medium and low soil nitrogen supply, respectively.  And, again, although elevated ozone alone reduced plant biomass, the simultaneous application of elevated CO2 completely ameliorated its detrimental effects on biomass production, irrespective of soil nitrogen supply.

The authors also determined that the CO2-enriched plants took up 25% less ozone than ambiently-grown control plants, due to CO2-induced reductions in stomatal conductance.

What it means
As the atmospheric CO2 concentration increases, spring wheat plants will likely experience greater protection against ozone-induced depressions in photosynthesis and growth, regardless of soil nitrogen availability.  Thus, spring wheat growers can anticipate greater yields in the future.

Reviewed 27 March 2002