What was done
The authors conducted two open-top chamber experiments in 1995 and 1996 at Wageningen, the Netherlands, wherein they grew early- and late-maturing potato (Solanum tuberosum L.) cultivars at atmospheric CO2 concentrations of 350 and 700 ppm.  Photosynthesis measurements were made throughout the growing seasons of each experiment, after which the potato tubers were harvested.

What was learned
Shortly after plant emergence, the extra CO2 increased leaf photosynthetic rates by approximately 80% in both cultivars.  Over the course of the growing season, however, this photosynthetic advantage gradually disappeared.  Nevertheless, the extra CO2 increased potato tuber yields by an average of 27% in 1995 and 49% in 1996.

What it means
First and foremost, enriching the air with CO2 increases yields of potato tubers.  Second, because the benefits (enhanced photosynthetic rates) of atmospheric CO2 enrichment steadily declined over the growing season, the authors calculated that only half of the potential yield enhancement the extra CO2 was capable of providing was realized.  They thus suggest that breeding and management techniques that might reduce this season-long decline in photosynthesis in the CO2-enriched treatment could be developed to take even greater advantage of the ongoing rise in the air's CO2 content.  Hence, not only do man's CO2 emissions provide an immediate boost to potato production, they provide us with an opportunity to use our ingenuity to wring even greater benefits out of the phenomenon.