Effect of CO2 Enrichment on Growth and Flowering of Phalaenopsis

To increase the photosynthesis of crop and improve plant quality, we evaluated the effect of elevated CO 2 on vegetative growth and flowering in Phalaenopsis 'Fuller's Pink Swallow'.Plants were exposed to 450 (control), 800, 1600, and 2400 μmol•mol -1 CO 2 for 31 weeks.The number of leaves, leaf length, and leaf width displayed greater increases in plants grown under 1600 and 2400 μmol•mol -1 CO 2 than in plants grown under 450 and 800 μmol•mol -1 CO 2 .The times to leaf initiation were reduced to 90.7 and 85.8 days in plants grown under 1600 and 2400 μmol•mol -1 CO 2 , respectively, compared with that of the control, 177.1 days.The leaf elongation rate was significantly increased in plants grown under 1600 and 2400 μmol•mol -1 CO 2 compared to plants grown under 450 and 800 μmol•mol -1 CO 2 .Plants grown under 1600 μmol•mol -1 CO 2 had the highest total number of flower buds among all plants grown under the four tested CO 2 concentrations.Leaf injuries were not observed in any plants regardless of CO 2 concentration, but flower bud abortion and bud withering were observed in CO 2 -enriched plants, especially in plants grown under 1600 and 2400 μmol•mol -1 CO 2 .Plants subjected to long-term CO 2 elevation of over 800 μmol•mol -1 displayed increased biomass production despite a concomitant reduction in the number of buds.These results showed that 1600 and 2400 μmol•mol -1 CO 2 significantly enhanced the vegetative growth of Phalaenopsis.However, long-term exposure to high CO 2 concentrations can adversely affect the flowering of Phalaenopsis, and result in reduced flower production and increased flower bud abortion.