Effect of CO₂ Enrichment on Growth and Flowering of Phalaenopsis

Abstract

To increase the photosynthesis of crop and improve plant quality, we evaluated the effect of elevated CO₂ on vegetative growth and flowering in Phalaenopsis ‘Fuller’s Pink Swallow’. Plants were exposed to 450 (control), 800, 1600, and 2400 μmol·mol⁻¹ CO₂ 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 CO₂ than in plants grown under 450 and 800 μmol·mol⁻¹ CO₂. The times to leaf initiation were reduced to 90.7 and 85.8 days in plants grown under 1600 and 2400 μmol·mol⁻¹ CO₂, 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 CO₂ compared to plants grown under 450 and 800 μmol·mol⁻¹ CO₂. Plants grown under 1600 μmol·mol⁻¹ CO₂ had the highest total number of flower buds among all plants grown under the four tested CO₂ concentrations. Leaf injuries were not observed in any plants regardless of CO₂ concentration, but flower bud abortion and bud withering were observed in CO₂-enriched plants, especially in plants grown under 1600 and 2400 μmol·mol⁻¹ CO₂. Plants subjected to long-term CO₂ 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 CO₂ significantly enhanced the vegetative growth of Phalaenopsis. However, long-term exposure to high CO₂ concentrations can adversely affect the flowering of Phalaenopsis, and result in reduced flower production and increased flower bud abortion.