This study investigated the photosynthetic responses of the CAM ornamental plant Schlumbergera truncata ‘Pink Dew’ under low-temperature greenhouse conditions to evaluate the potential for energy-saving cultivation. Greenhouse production requires substantial energy for heating, and reducing temperature is a possible strategy to save energy. However, low temperatures can suppress photosynthesis and plant growth. CAM plants, which absorb CO2 mainly at night, may respond differently to temperature, making it important to determine temperature ranges that maintain carbon assimilation while reducing energy use. Plants were grown in a greenhouse at average temperatures of 15/11°C (January, early flowering) and 21/12°C (March, late flowering). Gas exchange, chlorophyll fluorescence (Fv/Fm), and growth characteristics were measured, with comparisons made between top and second phylloclades. Results showed that during the early-flowering period, total net CO2 uptake was negative, indicating suppressed carbon assimilation under low temperature. During the late-flowering period, net CO2 uptake became positive, suggesting recovery of photosynthetic activity as temperatures increased. The second phylloclades generally exhibited higher CO2 uptake than the top phylloclades. The maximum quantum yield of PSII (Fv/Fm) increased from early to late flowering but remained below optimal values, indicating that plants experienced low temperature stress but maintained moderate photosynthetic function, suggesting some degree of acclimation. Morphological observations showed phylloclade discoloration and occasional lesions, which were consistent with symptoms of cold stress, although plants continued to grow and produce flower buds. Overall, the results indicate that low temperatures below the optimal range can suppress photosynthesis in S. truncata, but the plants retain a capacity for acclimation and recovery. These findings contribute to understanding the temperature sensitivity of CAM photosynthesis and may help define energy-saving temperature strategies in greenhouse cultivation.

Introduction
Materials and Methods
    Plant Material
    Experimental Environment Conditions
    Gas Exchange Measurements
    Chlorophyll Fluorescence Measurements
    Plant Growth and Biomass Parameters
Results
Discussion
Acknowledgments
References

• Jae Suk Lee(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)
• Myung Syun Shim(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