What was done
The authors enclosed branchlets of 30-m tall Luehea seemannii trees in small open-top chambers suspended within their upper canopies and exposed them to atmospheric CO2 concentrations of 360 and 750 ppm for nearly 40 weeks to study the effects of elevated CO2 on photosynthesis, growth, and reproduction in this deciduous tropical tree species.

What was learned
Leaves of branchlets grown in elevated CO2 displayed net photosynthetic rates that were approximately 30% greater than those observed in leaves of ambiently-grown branchlets.  However, the additional carbohydrates produced by this phenomenon were not used by CO2-enriched branchlets to increase leaf growth or reproductive efforts, but rather they were stored away in terminal woody tissues.  This observation led the authors to suggest that enhanced carbohydrate storage in terminal branchlets may facilitate greater first flush leaf growth the following year.

What it means
As the CO2 content of the air continues to rise, mature tropical trees --like Luehea seemannii-- will probably exhibit increased rates of net photosynthesis, thereby leading to enhanced carbohydrate production.  Whether or not additional carbohydrates are used immediately, or stored away for later use, it is likely that their utilization will ultimately increase tree biomass and contribute to the great carbon sink that exists within tropical forests.