Action spectra for photosynthetic adaptation in Scenedesmus obliquus |
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Authors: | Jens Thielmann Paul Galland |
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Institution: | (1) Fachbereich Biologie/Botanik, Philipps-Universität Marburg, Lahnberge, W-3550 Marburg, Germany |
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Abstract: | Photosynthetic adaptation of the unicellular green alga Scenedemus obliquus to different light conditions was investigated with respect to chlorophyll synthesis. Cultures were grown under white light (20 W · m–2) from fluorescent lamps and were then transferred and subjected to the actual adaptation regime which consisted of a 24-h irradiation by different fluence rates and wavelengths. Fluence rate-response curves for chlorophyll synthesis were measured between 4 · 10–2 and 1 · 102 W · m–2. In white light from incandescent lamps, in blue and red light the fluence rate-response curves for chlorophyll (Chl) a and also for Chl b were bell-shaped. In red light the threshold was about the same as under blue light. The maximal amounts of Chl a and b were about twofold increased under blue light relative to the values obtained with red light. Action spectra for the stimulation of chlorophyll synthesis (Chl a + Chl b) as well as those for the separate chlorophylls showed two maxima near 450 and 500 nm. However, the action spectrum for Chl b synthesis demonstrated a considerably higher value in the 450-nm peak. Experiments with the photosynthesis inhibitor 3-(3,4-dichlorphenyl)-1,1-dimethylurea (DCMU) indicated that photosynthetic energy supply supported the photostimulation of chlorophyll synthesis. The action spectra indicate the cooperation of two photoreceptors. The 460-nm peak is attributed to the typical blue-light receptor, being more active in Chl b formation. The peak at 500 nm may represent carotenoproteins acting as an accessory pigment system.Abbreviations PCV
packed cell volume
- Chl
total amount of chlorophyll
- Chl a, b
chlorophyll a, b
- DCMU
3-(3,4-dichlorphenyl)-1,1-dimethylurea
This project was supported by the Deutsche Forschungsgemeinschaft. We thank Ms. K. Bölte for technical assistance. |
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Keywords: | Action spectroscopy Blue-light photoreceptor Chlorophyll biosynthesis Photosynthetic adaptation Scenedesmus |
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