LAUSR

Abstract We investigated the flowering and photosynthetic responses of Phalaenopsis Queen Beer ‘Mantefon’ to CO2 enrichment and light level. Potted plants at the flowering stage were supplied with low light level (LL; 90 ± 10 μmol m−2 s−1) or high light level (HL; 260 ± 40 μmol m−2 s−1) using three−wave cool white fluorescent lamps and metal halide lamp and different levels of CO2. Carbon dioxide was supplied to the plants, which perform crassulacean acid metabolism, during their dark period at three concentrations: 400 (control), 800, and 1200 μmol mol−1 CO2. More flowers and lateral branches were produced by plants grown under HL than the control plants grown under LL, and there were more visible floral buds in the plants grown under HL than those grown LL, regardless of CO2 concentration. Net CO2 assimilation rate was higher in plants exposed to 800 and 1200 μmol mol−1 CO2 under LL and 1200 μmol mol−1 CO2 than the control plants under LL and HL. We conclude that photosynthesis is enhanced in CO2-enriched plants, and lateral branch and floral bud production are maximized at the high light level used here in Phalaenopsis Queen Beer ‘Mantefon’.