Background
The authors indicate that Lisianthus (Eustoma grandiflorum (Raf.) Shin) - also known as Texas Bluebell, Prairie Gentian and Tulip Gentian - "is a popular ornamental cut flower because of its long vase life and range of flower colors." And in Japan, where they reside, they say that flowers are produced on the plants year-round, but that "winter conditions are not favorable for flower production due to low sunlight levels."

What was done
Cognizant of the fact that atmospheric CO2 enrichment "benefits the production of horticultural crops (Gruda, 2005; Mortensen, 1987) by reducing the negative effects of other environmental factors, such as low light conditions (Gruda, 2005)," the three researchers say they "investigated the effect of CO2 enrichment, after the flower-budding stage, on the growth, flowering and cut flower quality of a double- and early-flowering variety of Eustoma grown in a region of Japan with low sunlight levels during winter."

What was learned
Ushio et al. report that in the greenhouse study they conducted under winter sunlight conditions, plants exposed to air of 1000 ppm CO2 for an additional 66 days after the flower-budding stage of growth was reached, as compared to plants that remained exposed to normal ambient air, grew 3.7% taller, produced 31.5% more fresh weight, 26.6% more leaf area, 15.8% more flower buds, and an amazing 190% more open flowers. And they say that these growth and developmental enhancements were also accomplished in a significantly shortened growth period in the CO2-enriched treatment.

What it means
In addition to the huge increase in the number of flowers produced in their CO2-enriched-air treatment, the Japanese scientists say their findings suggest that "the CO2 enrichment of Eustoma not only improves the quality of cut flowers but also shortens the period to harvest during winter." And that such results are not unusual, they say that "an increase in the total number of flower buds and open flowers after CO2 enrichment has been reported for many other plants, including chrysanthemum (Mortensen, 1986), rose (Mortensen, 1987, 1995), and dianthus (Mortensen, 1987)."

References
Gruda, N. 2005. Impact of environmental factors on product quality of greenhouse vegetables for fresh consumption. Critical Reviews in Plant Sciences 24: 227-247.

Mortensen, L.M. 1986. Effect of intermittent as compared to continuous CO2 enrichment on growth and flowering of Chrysanthemum x morifolium Ramat. and Saintpaulia ionantha H. Wendl. Scientia Horticulurae 29: 283-289.

Mortensen, L.M. 1987. Review: CO2 enrichment in greenhouses. Crop responses. Scientia Horticulurae 33: 1-25.

Mortensen, L.M. 1995. Effects of temperature, carbon dioxide concentration, day length and photon flux density on growth, morphogenesis and flowering of miniature roses. Acta Horticulurae 378: 63-70.