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- Richardson, Katherine, et al.
(författare)
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The relationship between photosynthesis measured by C-14 incorporation and by uptake of inorganic carbon in unicellular algae
- 1984
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 81:3, s. 241-250
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Tidskriftsartikel (refereegranskat)abstract
- The traditional 14C method of estimating photosynthetic rates was compared with net photo-synthesis in two species of unicellular algae. Net photosynthesis was defined as the disappearance of inorganic carbon from the algal medium and was determined using a described infra-red gas analyser (IRGA) technique. For Amphidinium carterae Hulbert, the 14C method always led to lower calculated rates of photosynthesis than the IRGA technique. This difference was, on average, ≈100%. For Scenedesmusobliquus (Turpin) Kützing, the 14C method could lead to over-estimates, good agreement with, or underestimates of net photosynthesis. Although the under-estimates were only of the order of 15%, the over-estimates were in some cases > 100%. There is some indication that respiration rate is an important factor in the relationship between photosynthetic rates calculated by the two methods for this organism.
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- Samuelsson, Göran, 1951-
(författare)
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The use of fluorescence techniques for the study of some membrane-bound photosynthetic properties and some effects of copper on the thylakoid membrane
- 1981
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lyophilized pea chloroplasts were extracted in a stepwise manner in an organic solvent (petroleum ether) with increasing polarity which was obtained by addition of small amount of ETOH (0-1 %). Absorption and low temperature fluorescence emission spectra were measured on both the extracted thylakoids and on isolated chlorophylI-protein complexes. Extraction of chlorophyll from the membrane increased (and the ratio of chlorophyl l a/b decreased) with increasing polarity of the solvent. The gel scan revealed that after extraction with petroleum ether, CPa.. was lost from the gel and after extraction with petroleum ether +1 % ETOH only the CPa/b was left together with SDS-free chlorophyll. This shows that the chlorophyll in CPa/b are situated in a less hydrophobic environment than chlorophyll in CPa|| and CPa|. The long wavelength absorbing and emitting chlorophyll fraction associated to CPaj was found to be easily removed from the membrane. This caused a blue shift in the low temperature fluorescence emission peak and in the red absorption peak and it was also accompanied by a decrease in carote-noid absorption in isolated CPa|. It was found in different plant material lacking $-carotene in CPàj that a strong correlation between ß-carotene in CPa. and the existence of the long wavelength chlorophyll in isolated cPa. existed. Based on these data, it was suggested that excited chlorophyll can transfer energy in excess to ß-carotene by a triplet--triplet transfer.A method based on in vivo chlorophyll £ fluorescence was developed for studying photosynthetic capacity in unicellular algae. It was shown that DCMU-induced fluorescence increase was a good measure of photosynthetic capacity in four species of green algae tested.The effect of copper chloride on photosynthetic electron transport and chlorophyl1-protein complexes was studied in spinach chloroplasts. Copper(11) inhibited a PS I i reaction H2O—> DPIP, a PS I reaction Asc/DPIP —> NADP and the overall electron transport H2O —> NAOP to different degrees. Chlorophyll protein complexes were only slightly affected by copper(ll) but with both copper and ascorbate in the reaction media, a rapid membrane destruction occurred. This was probably caused by a free radical reaction catalyzed by copper(ll).
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