What was done
The authors grew small and large bulbs of Hippeastrum (which produces amaryllis flowers) in greenhouses receiving atmospheric CO2 concentrations of 350 and 1000 ppm about four hours of each day for 233 days with different combinations of nitrogen and potassium fertilization to study the interactive effects of these parameters on bulb size.

What was learned
Elevated CO2 consistently increased bulb size across all nitrogen and potassium concentrations, with initially larger bulbs yielding the greatest size of final bulbs.  However, on a percentage basis, smaller bulbs were slightly more responsive to atmospheric CO2 enrichment than were larger bulbs.  Indeed, under optimal nitrogen and potassium fertilization, the 650-ppm increase in the air's CO2 concentration increased the size of smaller and larger bulbs by about 18 and 14%, respectively.

What it means
As the CO2 content of the air increases, it is likely that bulbs of Hippeastrum will increase their size, thus leading to enhanced bulb quality and flower (amaryllis) production.