| In this paper, the potted plants of the two-year-old Citrus cv. Xiangshanhong were cultivated under heat insulation dysprosium lamps which have similar spectrum to sunlight, and five color films were used to cover plant leaves. Cultivation conditions at (25±1)℃, 800μmol·m-2·s-1 and 35～45%RH. The spectrum of the white film, red film, yellow film, blue film, green film were full length white light, 600-800 nm, 450-800 nm, 380-455 + 622-770 nm, 700-800 ran separately. Gas exchange system (HCM-1000, Walz, Germany) ,a portable fluorometer (PAM-2000, Walz, Germany) , SDS-PAGE and Western-blotting analysis were used to analyse changes of gas exchange parameters, chlorophyll fluorescence, D1 protein and FtsH metalloprotease. The plants were irradiated under dysprosium lamps directly for photoinhibition treatment, and the light intensity was 1800μmol·m-2·s-1.The main results of this study are as follows:1. Pn, Tr and Gs in Citrus cv. Xiangshanhong leaves under different light qualities after five weeks were in the order: white film> yellow film >blue film >red film >green film. Otherwise, the capability to utilize light, the activity of RuBPCase and photorespiration determined under full length white light and 450-800 nm light were higher than other light qualities, suggesting that 400-700 nm visible light is the basis of the citrus photosynthesis, and 450-600 light is the most important.2. Fv/Fm declined and Fo increased in Citrus cv. Xiangshanhong leaves under green film after five weeks. qP, ETR andΦPSⅡdetermined under different light films: yellow film > white film >blue film >red film >green film, larger decline occurred under red and green films. Kinetic curve of fluorescence induction fast phase indicated that QA reduction was: yellow film > white film >blue film >red film >green film, proportion of QB-non-reducing PSII was: green film> red film>blue film>yellow film > white film. These results suggested that white light and full of 450-600 nm light was favor in electron transport of PSⅡand the conversion of light energy to chemical energy. The spectrum lack of 400-700 nm and 300-400 nm made the proportion of opened PSII reaction centers decreased, electron transport rate was also inhibited in part. While 600-800 nm light almost made the PSⅡreaction centers closed and its activity also declined.3. The content of D1 protein in Citrus cv. Xiangshanhong leaves showed significant difference under different light qualities after five weeks. Compared with white film, Dl protein slightly decreased under yellow film, reduced by 62.2% and 59.2% under red and blue films separately. Moreover, Dl protein dramatically decreased under green film, which was only 11.4% of that under white film. This indicated that the synthesis of D1 protein need 450-600 nm visible light.4. Fv/Fm decreased after 2 h high light (1600～1800μmol·m-2·s-1) treatment. It can be recovered to the original level after 6 h low light (200～300μmol·m-2·s-1) treatment under white, yellow and blue films, while it can't be recovered under dark, red and green films. It was in the order: white film> yellow film >blue film >red film >green film, dark, which indicate that full length white light and 450-600 nm light was in favor of the repair of photosystemⅡfrom photoinhibition.5. It was showed that the content of the D1 protein and FtsH was reduced due to photoinhibition. It can be recovered to the original level after 6 h low light (200～300μmol·m-2·s-1) treatment under white, yellow and blue films, while it was recovered slowly under red film, and almost can not be recovered under green film. FtsH gradually increased during repair of photosystemⅡ, suggesting that FtsH indeed plays an important role in Dl protein degradation and the repair of photosystemⅡ.
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