What was done
The authors grew dwarf apple (Malus domestica Borkh. Cv. Fuji) saplings in controlled environment chambers for three years at atmospheric CO2 concentrations of 360 and 650 ppm in combination with ambient and elevated (ambient + 5°C) air temperatures to study the effects of elevated CO2 and temperature on photosynthesis and growth in this fruit species that is commercially important in Korea.

What was learned
After three years of treatment exposure, elevated CO2 continued to stimulate photosynthetic rates by 38 and 49% at ambient and elevated air temperatures, respectively.  In addition, saplings exposed to elevated CO2 concentrations shifted their optimal photosynthetic temperature upward by approximately 4°C.  Tree height was not affected by elevated CO2 at normal temperatures; but it was increased by 20% in the elevated temperature treatment.  And in the most important growth category of all, the CO2-enriched trees produced three times more fruit (on a per-tree weight basis) at elevated as opposed to ambient air temperature.

What it means
As the air's CO2 concentration continues to rise, it is likely this dwarf apple species will exhibit significant increases in both photosynthesis and apple production.  And if air temperatures also rise, photosynthetic rates will likely be even greater, due to the positive interaction between elevated CO2 and temperature plus the large CO2-induced increase in the optimal temperature for photosynthesis in this species.  Thus, apple yields should substantially increase in a future CO2-enriched environment, especially if air temperature rises a few degrees.