한국원예학회지(2004) Abstract. The effect of light sources that have different photon flux and spectral distribution on photosynthetic efficiency was studied in chrysanthemum (Dendranthema grandiflorum). To compare photosynthetic efficiency under each light source, yield photon flux between 300 and 800 nm was determined as the product of the spectral photon flux and the relative quantum efficiency, which was varied considerably depending on the light sources. The yield photon flux of sunlight increased from 330 nm and the highest peak was recorded in red light region and then decreased rapidly at longer than 674 nm. When comparing the values of yield photon flux among artificial lamps, high-pressure sodium lamp gave the highest followed by metal halide, fluorescent tube, and incandescent lamps. When chrysanthemum cv. Puma was grown under different artificial light sources, photosynthetic rate and leaf chlorophyll contents were in the same order where high-pressure sodium lamp were highest and incandescent lamp least. These results were consistent with that of photosynthetically active radiation in the 400-800 nm region. Spectral distribution also affected photosynthetic efficiency but less significant than the irradiance level.