What was done
The authors grew strawberries in controlled glasshouses exposed to atmospheric CO2 concentrations of 390 and 560 ppm for nearly three months.  In addition, the strawberries were supplied with fertilizers containing three levels of nitrogen.  Thus, the authors were able to study the direct and interactive effects of elevated CO2 and nitrogen supply on strawberry growth.

What was learned
Elevated CO2 increased rates of net photosynthesis and total plant dry weight at all nitrogen levels.  Although these increases were not significant, they did, nonetheless, provide CO2-enriched plants with enough additional sugar and physical mass to support significantly greater numbers of flowers and fruits than plants grown at 390 ppm CO2.  This effect consequently led to total fresh fruit weights that were 42 and 17% greater in CO2-enriched plants that received the highest and lowest nitrogen levels, respectively.  In addition, elevated CO2 increased the nitrogen-use efficiency of these plants by 23 and 17%, respectively.

What it means
As the amount of CO2 in the atmosphere increases, it is likely that strawberry plants the world over will exhibit increased rates of photosynthesis, regardless of soil nitrogen fertility.  The increased supply of carbohydrates provided by this phenomenon can be used to increase plant size, as well as numbers of flowers and fruits.  Ultimately, these effects will lead to increased yields, which should be very important to commercial strawberry growers and home gardeners.