Light-induced changes of photosystem II activity in dark-grown Scots pine seedlings |
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Authors: | Stefan Jansson,Ivar Virgin,Petter Gustafsson,Bertil Andersson,Gunnar Ö qulst |
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Affiliation: | Dept of Plant Physiology, UmeåUniv., S-901 87 Umeå, Sweden;Dept of Biochemistry, Arrhenius Laboratory, Stockholm Univ., S-106 91 Stockholm, Sweden. |
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Abstract: | Both chlorophyll a and b and polypeptides of the photosynthetic apparatus are found in gymnosperm seedlings. germinated and grown in absolute darkness. The photosystem II (PSII) activity is, however, limited, probably due to an inactive oxygen evolving system. In the present study dark-grown seedlings of Scots pine ( Pinus sylvestris L.) were transferred to light and changes in antenna size and the activation process of PSII were investigated using fluorescence measurements and quantitative western blotting. It was found that the activation process is rapid, requires very little light and that strong light inhibits the process. It takes place without any changes in the primary reactions of PSII. Furthermore, all polypeptides except the major light-harvesting chlorophyll a/b -binding protein complex of PSII (LHCII) were present in dark-grown seedlings in amounts comparable to the light treated control. The dark-grown seedlings had the same LHCII polypeptide composition as light treated seedlings, and the LHCII present seemed to be fully connected to the reaction centre. The results indicate that activation of PSII in dark-grown conifer seedlings resembles the photoactivation process of angiosperms. This implies that the fundamental processes in the assembly of the photosystem II complex is the same in all plants, but that the regulation differs between different taxa. |
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Keywords: | Low temperature fluorescence oxygen evolving complex photoactivation photosystem II Pinus sylvestris room temperature fluorescence Scots pine |
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