Response of photosynthetic systems to salinity stress in the desert cyanobacterium Scytonema javanicum |
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| Authors: | Jinlu Hu Liang Jin Xiaojuan Wang Wenkai Cai Yongding Liu Gaohong Wang |
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| Institution: | 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan, Hubei 430072, China;2. School of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, Gansu 730020, China;3. University of the Chinese Academy of Sciences, Beijing 100039, China |
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| Abstract: | The present study investigated the physiological and biochemical characteristics of Scytonema javanicum, a pioneer species isolated from desert biological crusts, under salinity stress. Pigment analysis showed that salinity decreased chlorophyll a and phycocyanin content, while low salinity increased carotenoid concentration and high salinity decreased carotenoid concentration. Salinity also inhibited CO2 assimilation rate and photosynthetic oxygen evolution in this cyanobacterium. Chlorophyll a fluorescence transient parameters (φPo, φEo, ψO, RC/ABS, RC/CS, PIABS, and PICS) were decreased under salt stress, while dVo/dto(Mo), Vj and φDo were increased. The decrease of ETRmax and Yield and the change of chlorophyll a fluorescence transients showed that salt stress had an important influence on photosynthesis. These results indicated that the effects of salinity stress on photosynthesis in S. javanicum may depend on the inhibition of electron transport and the inactivation of the reaction centers, but this inhibition may occur in the electron transport pathway at the PSII donor and acceptor sites. |
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| Keywords: | Ca chlorophyll a Cc carotenoid DCMU 3-(3 4-dichlorophenyl) -1 1-dimethylurea phycocyanin content phycocyanin PEA plant efficiency analyzer PI the performance index of PSII PSII photosystem II RC/CS the amount of active PSII reaction centers per excited cross section RC/ABS the total number of active reaction center per absorption φPo the quantum yield of primary photochemistry φEo the quantum yield for electron transport Ψo the efficiency per trapped excitation OJIP fluorescence induction transient defined by the names of its intermediate steps O level fluorescence level at 20 μs J level fluorescence plateau at 2 ms I level fluorescence plateau at 30 ms P level the maximum fluorescence level |
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