What was done
The authors used a branch bag technique to expose new foliage on branches of 30-year-old Norway spruce trees to ambient and elevated (ambient plus 340 ppm) levels of CO2.  They then measured rates of net photosynthesis, dark respiration and stomatal conductance.  Foliar concentrations of nonstructural carbohydrates were also determined.

What was learned
Elevated CO2 enhanced rates of light-saturated net photosynthesis by 50-55% and increased the amounts of the nonstructural carbohydrates that were studied by an average of 33%.  Respiration was 18% higher with atmospheric CO2 enrichment, possibly due to greater energy demands required for transporting the increased amounts of carbohydrates into the phloem.  Atmospheric CO2 enrichment had no effect on stomatal conductance, in agreement with observations made on other conifer species.

What it means
Norway Spruce trees will likely exhibit increased rates of photosynthesis as the CO2 content of the air continues to rise, which should lead to increased levels of carbohydrate production that can be used to facilitate growth.  Because stomatal conductance in Norway spruce trees appeared to be unaffected by elevated CO2, this additional growth will occur without increasing the transpirational water loss rates of individual needles, thereby significantly increasing their water-use efficiencies.