Schlumbergera truncata absorbs CO2 through its mature phylloclades during the night, and can use a substantial amount of CO2 without requiring ventilation. This study investigated the growth and photosynthetic responses of S. truncata ‘Red Candle’ at two CO2 levels—ambient (≈ 400 μmol･mol-1) and elevated (≈ 1000 μmol･mol-1). At 0–8 weeks after treatment (WAT), width and length of mature phylloclade and length of immature phylloclade did not differ significantly among the CO2 treatments. At 4–8 WAT, number of branches and phylloclades were significantly greater in plants grown under ambient CO2 than those under elevated CO2. Net CO2 uptake was highest in mature phylloclades of plants grown under ambient and elevated CO2 regimes at night, at 2.51 and 1.30 μmol·CO2·m-2·s-1, respectively. However, no statistically significant variation was observed at 6 WAT, and stomatal conductance was significantly affected only by CO2 uptake time at 6 and 8 WAT. Water-use efficiency of mature and immature phylloclades at night increased with increase in CO2 levels (r = 0.7462 and 0.9312, respectively). At 123 days after treatment, plants grown under elevated CO2 had 82.7 floral buds, compared to 72.1 buds in those under ambient CO2. However, this difference was not statistically significant. Moreover, S. truncata grown under elevated CO2 exhibited decreased growth and photosynthesis, whereas the number of floral buds did not exhibit any significant differences among the treatments.

Introduction
Materials and Methods
    Plant materials and growth conditions
    CO2 supply
    Data collection
    Statistical analysis
Results
    Phylloclade growth and plant biomass
    Photosynthetic characteristics and maximumquantum yield of PSII (Fv/Fm)
    Flowering
Discussion
Acknowledgments
References

• Seo Hee Jung(Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women’s University, Nowon-gu, 01797 Seoul, Korea)
• Seo Youn Lee(Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women’s University, Nowon-gu, 01797 Seoul, Korea)
• Jae Suk Lee(Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women’s University, Nowon-gu, 01797 Seoul, Korea)
• Yoon Jin Kim(Department of Horticulture, Biotechnology and Landscape Architecture, Seoul Women’s University, Nowon-gu, 01797 Seoul, Korea) Corresponding author