TITLE	Effects of b-carotene feeding on chlorophyll fluorescence, zeaxanthin content, and D1 protein turnover in rice (Oryza sativa L.) leaves exposed to high irradiance
AUTHOR	Cheng-Wei Yang* South China Institute of Botany, The Chinese Academy of Sciences, Guangzhou 510650, The People's Republic of China Chang-Lian Peng South China Institute of Botany, The Chinese Academy of Sciences, Guangzhou 510650, The People's Republic of China Jun Duan South China Institute of Botany, The Chinese Academy of Sciences, Guangzhou 510650, The People's Republic of China Yi-Zhu Chen South China Institute of Botany, The Chinese Academy of Sciences, Guangzhou 510650, The People's Republic of China
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ABSTRACT	To examine the mechanism of photoprotective effect of exogenous b-carotene against photoinhibition under strong light conditions, leaves of rice (Oryza sativa L.) were fed with 30 mmol/L b-carotene through the transpiration stream at a PPFD of 20 µmol m-2 s-1 for 3 h. The leaves were then exposed to strong light at a PPFD of 2000 µmol m-2 s-1 for another 3 h. The photo-induced decrease in activity of PS2 in b-carotene fed leaves, as estimated in terms of the changes of Fv/Fm, photochemical quenching (qP), and PSII electron transport rate (JF), was smaller than that in control leaves during exposure to strong illumination. However, the presence of chloramphenicol produced no significant difference. Furthermore, feeding of b-carotene increased endogenous b-carotene content. In addition, the content of zeaxanthin and the xanthophyll cycle pigments pool size (V+A+Z) were increased in comparison with control leaves when the leaves were exposed to high light for 3 h. However, no significant difference was observed in the presence of chloramphenicol. These results indicate that the photoprotective effect of b-carotene feeding can be partially explained by the conversion of b-carotene to zeaxanthin, a process involved in the rapid D1 protein turnover during the reassembly of PS2 in high irradiance.
KEYWORD	b-Carotene; Chlorophyll fluorescence; D1 protein turnover; High irradiance; Xanthophyll cycle; Zeaxanthin;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 43 Number 3 July 2002, page 181-185, 5 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China