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Effects of Elevated CO2 and Ozone on Winter Wheat
Heagle, A.S., Miller, J.E. and Pursley, W.A.  2000.  Growth and yield responses of winter wheat to mixtures of ozone and carbon dioxide.  Crop Science 40: 1656-1664.

What was done
The authors grew several soft red winter wheat (Triticum aestivum L.) cultivars in
open-top chambers at atmospheric CO2 concentrations of 380, 540 and 700 ppm in combination with atmospheric ozone concentrations of 27, 45 and 90 ppb to determine the interactive effects of elevated CO2 and O3 on growth and yield in this agronomic cereal crop.

What was learned
Elevated CO2 suppressed foliar injury caused by elevated O3, especially in some of the more O3-sensitive cultivars used in this study.  In addition, atmospheric CO2 enrichment to 700 ppm almost completely protected such cultivars from the negative effects of elevated O3 on seed yield.  At ambient CO2 concentrations, for example, elevated O3 reduced seed yield by 48% in an O3-sensitive cultivar.  However, at an atmospheric CO2 concentration of 700 ppm, yield reductions in this same O3-susceptible variety were only 8%.  Thus, atmospheric CO2 enrichment had a strong ameliorating effect on the negative influences of elevated O3 on growth and yield of O3-susceptable winter wheat cultivars.

What it means
As the CO2 content of the air continues to rise, it will likely offer significant protection against O3-induced reductions in growth and yield of winter wheat varieties.  In fact, yield reductions from tropospheric ozone may in some cases be completely eliminated.  Thus, winter wheat growers can anticipate greater yields in the future, due to this beneficial effect of the rising atmospheric CO2 concentration.