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Effects of Elevated CO2 on Photosynthesis and Growth in Peanut
Stanciel, K., Mortley, D.G., Hileman, D.R., Loretan, P.A., Bonsi, C.K. and Hill, W.A.  2000.  Growth, pod and seed yield, and gas exchange of hydroponically grown peanut in response to CO2 enrichment.  HortScience 35: 49-52.

What was done
Peanut (Arachis hypogaea) plants were grown hydroponically for 110 days in controlled environment chambers receiving atmospheric CO2 concentrations of 400, 800 and 1200 ppm to determine the effects of elevated CO2 on photosynthesis and growth.

What was learned
Plants grown at 800 ppm CO2 had net photosynthetic rates that were 29% greater than those of plants grown at 400 ppm CO2, while plants grown at 1200 ppm CO2 displayed photosynthetic rates that were 24% lower than those exhibited by ambiently-grown plants.  Nevertheless, the number of pods, pod weight and seed dry weight per area all increased with atmospheric CO2 enrichment from 400 to 1200 ppm.  The harvest index, for example, which is the ratio of the seed dry weight to the total pod dry weight, was 19 and 31% greater at 800 and 1200 ppm CO2, respectively, than it was at 400 ppm CO2.  In addition, as the atmospheric CO2 concentration increased, stomatal conductance decreased, becoming 44 and 50% lower at 800 and 1200 ppm than it was at 400 ppm CO2.  Thus, atmospheric CO2 enrichment also reduced transpirational water losses.

What it means
As the atmospheric CO2 concentration increases, it is likely that peanut plants will exhibit increases in both photosynthesis and yield while reducing the amount of water required for optimal growth and development.  Thus, even if peanut acreage remains constant or is slightly reduced in the future, it is conceivable that yields will still be greater than they are today.

Reviewed 9 August 2000