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Effects of Variable CO2 Concentration and Light Intensity on Photosynthesis in Winter Wheat
Harnos, N., Tuba, Z. and Szente, K.  2002.  Modelling net photosynthetic rate of winter wheat in elevated air CO2 concentrations.  Photosynthetica 40: 293-300.

What was done
The authors grew winter wheat (Triticum aestivum L. cv. Emma) in open-top chambers maintained at atmospheric CO2 concentrations of 365 and 700 ppm to study the effects of elevated CO2 on photosynthesis in this important grain crop species.

What was learned
Data obtained at the beginning of flowering and grain filling revealed that elevated CO2 increased foliar concentrations of chlorophyll a, chlorophyll b and carotenoids (x and c) by averages of 23, 5 and 48%, respectively.  In addition, elevated CO2 stimulated photosynthetic rates to a greater extent under light-limiting than under non-light-limiting conditions.  In fact, twice-ambient CO2 concentrations increased net photosynthesis rates by approximately 100% in upper-canopy leaves and by about 770% further down in the canopy, where light intensity was 60% less than in the upper canopy.

What it means
As the atmospheric CO2 concentration increases in the years ahead, winter wheat plants will likely respond by exhibiting enhanced rates of photosynthesis, even in leaves deep within crop canopies, where irradiance is severely reduced due to shading by upper-canopy leaves.  The present data clearly indicate, for example, that the greater pigment contents of the CO2-enriched plants allowed them to significantly enhance their radiation-use efficiency and maintain significantly greater rates of photosynthesis throughout their entire canopies.  Hence, farmers of the future in a world of higher atmospheric CO2 concentration should be able to remove much heftier grain harvests from their fields than they do currently.

Reviewed 15 January 2003