O2 evolution and cyclic electron flow around photosystem I in long-term ground batch culture of Euglena gracilis |
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Authors: | Yanjun An Suqin Wang Zongjie Hao Yiyong Zhou Yongding Liu |
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Institution: | 1. Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China;2. Graduate University of Chinese Academy of Sciences, Beijing 100049, PR China |
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Abstract: | Based on the purpose of better exploring the function of green producers in the closed aquatic biological life support system, the condition of dynamic O2 evolution and performance of cyclic electron flow around photosystem I (CEF-PSI) in long-term ground batch culture of Euglena gracilis were studied, the relationship between linear electron flow (LEF) and CEF-PSI was revealed, the function of CEF-PSI was investigated. Excellent consistency in O2 evolution pattern was observed in cultures grown in both closed and open containers, O2 evolution was strictly suppressed in phase 1, but the rate of it increased significantly in phase 2. CEF-PSI was proposed to be active during the whole course of cultivation, even in the declining phase 3, it still operated at the extent of 47–55%. It is suggested that the relationship between LEF and CEF-PSI is not only competition but also reciprocity. CEF-PSI was proposed to contribute to the considerable growth in phase 1; it was also suggested to play an important protective role against photosystem II (PSII) photoinhibition at the greatly enhanced level (approximately 80–95%) on the 2nd day. Our results in this research suggest that E. gracilis had very particular photosynthetic characteristics, the strict O2 evolution suppression in the initial culture phase might be a special light acclimation behavior, and CEF-PSI could be an important mechanism involved in this kind of adaptation to the changeable light environment. |
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Keywords: | CEF-PSI cyclic electron flow around photosystem I LEF linear electron flow MD1 modified D1 medium MD1g MD1 + glucose MD1s MD1 + straw broth PSI photosystem I PSII photosystem II NPQ non-photochemical quenching PGC Photoperiod-grown cultures open system cultures grown in the 12:12 h light/dark cycle DGC Dark-grown cultures open system cultures grown in complete dark DCMU 3-(3&rsquo 4&rsquo -dichlorophenyl)-1 1-dimethylurea DBMIB dibromothymoquinone |
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