What was done
The authors grew wheat (Triticum aestivum) hydroponically in controlled environment chambers receiving atmospheric CO2 concentrations of 330 and 1200 ppm to study the effects of elevated CO2 on this important agronomic crop.

What was learned
Over the entire life cycle of wheat, from seedling development to seed production and senescence, plants grown at elevated CO2 concentrations displayed rates of net photosynthesis that were 13% greater than those of ambiently-grown plants.  In addition, elevated CO2 increased canopy quantum yield by 14%.  These phenomena likely contributed to the 13% observed increase in seed yield for CO2-enriched vs. non-CO2-enriced plants.

It is also interesting to note that atmospheric CO2 enrichment led to a 28% reduction in leaf nitrogen without affecting leaf chlorophyll content.  Thus, this reduction in leaf nitrogen must have been accompanied by changes in leaf protein contents, rather than in leaf pigment contents.

What it means
As the CO2 concentration of the air continues to rise, it is likely that wheat plants will exhibit enhanced rates of photosynthesis, which will lead to greater growth rates and a quicker closure of the crop canopy.  In turn, this will likely increase radiation capture by the canopy and further stimulate biomass production, including that associated with reproductive components.  Hence, wheat yields will likely rise in tandem with future increases in the CO2 content of the air.