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Effects of Elevated CO2 on Gas Exchange in Winter Wheat
Liu, H.Q., Jiang, G.M., Zhang, Q.D., Sun, J.Z., Guo, R.J., Gao, L.M., Bai, K.Z. and Kuang, T.Y.  2002.  Gas exchange responses to CO2 concentration instantaneously elevated in flag leaves of winter wheat cultivars released in different years.  Photosynthetica 40: 237-242.

What was done
The authors grew three widely-cultivated varieties of winter wheat (Triticum aestivum L. cv. Jingdong 8, Nongda 139 and Yanda 1817) in fields near Beijing, China, and subjected them to short-term atmospheric CO2 enrichment to study the instantaneous effects of elevated CO2 on gas exchange in the three varieties.

What was learned
Plants exposed to a doubled atmospheric CO2 concentration of 720 ppm displayed photosynthetic rates that were enhanced by 173% (Jingdong 8, released to growers in 1995), 88% (Nongda 139, released to growers in 1983) and 76% (Yanda 1817, released to growers in 1945).  In addition, the elevated CO2 increased the instantaneous water-use efficiencies of the three varieties by 81, 66 and 65%, respectively.

What it means
As the atmospheric CO2 concentration continues to rise, these popular Chinese-grown varieties of winter wheat will likely respond by exhibiting enhanced rates of photosynthesis and increased water-use efficiencies, which will likely allow greater wheat yields to be achieved in the future, even under conditions of mild to moderate water stress.  Interestingly, the greatest positive responses to atmospheric CO2 enrichment occurred in Jingdong 8, which is the most recently released variety of the three studied.  Thus, it would appear that traditional Chinese breeding and selection programs over the past half-century have fortuitously increased the gas exchange responsiveness of this winter wheat cultivar to atmospheric CO2 enrichment.

Reviewed 1 January 2003