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We evaluated the effects of light conditions on leaf gas exchange, chlorophyll content, and growth responses in the Oriental lily (Lilium auratum L.) cv. Sorbonne. The experiment involved application on increasing shade densities (0, 60, 75, and 80%) to Sorbonne, and was carried out in the Horqin Sandy Land of northern China. Shade tests showed that growth of the lily was primarily affected by the level of irradiance. Photoinhibition occurred in the 0 and 60% shade treatments, but not in the 75 and 80% shade treatments. Shade treatments led to increase in photosynthetic pigment content, enhancement in photosynthetic effi ciency, and finally increase in the commercial value of the lily. P n , on the other hand, was lowest in the 80% shade treatment. So irradiance less than that achieved in the 80% shade treatment limited carbon assimilation and led to decreased plant growth. Plants grown under 75% shade displayed the optimal traits determining commercial value (plant height, flower length, flower diameter). Trends in P max , AQY, LSP and LCP to shade confirmed that the lily is a shade tolerant plant. Excessive light, therefore, was the primary factors limiting lily quality. Growth under conditions of 75% shade is recommended to improve photosynthetic efficiency and alleviate photodamage, thus increasing the commercial value of the lily grown in the Horqin Sandy Land.Abbreviations: AQY-apparent quantum yield; Chl a-chloro phyll a; Chl b-chlorophyll b; E-transpiration rate; g s -sto matal conductance; LCP-light compensation point; LSPlight saturation point; PAR-photosynthetically active radiation; P max -maximum net photosynthetic rate; P n -net photosyn thetic rate; R D -respiration rate.

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