Light-induced inhibition of respiration in DCMU-poisoned Chlorella caused by photosystem I activity

1972 ◽  
Vol 50 (1) ◽  
pp. 13-21 ◽  
Author(s):  
D. F. Sargent ◽  
C. P. S. Taylor
Keyword(s):  
Oxygen Uptake ◽  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Photosystem I ◽  
Action Spectrum ◽  
Photosynthetic Oxygen Evolution ◽  
Intracellular Atp ◽  
Respiratory Inhibition ◽  
Cyclic Photophosphorylation ◽  
Photosynthetic Oxygen

We have demonstrated that the reduced net rate of oxygen uptake observed when DCMU-poisoned Chlorella are illuminated is a result of an inhibition of respiration rather than residual photosynthetic oxygen evolution. The action spectrum of the effect demonstrates that chlorophyll a is the main photoreceptor, implicating system I of photosynthesis. Studies using PMS, which is known to stimulate cyclic photophosphorylation by photosystem I, show that the respiratory inhibition is caused by a change in the intracellular ATP/ADP balance as a result of cyclic photophosphorylation.

Characterization of a Light-Induced Oxygen-Uptake in Tobacco Protoplasts

1979 ◽  
Vol 34 (7-8) ◽  
pp. 570-575 ◽  
Author(s):  
Georg H. Schmid ◽  
Pierre Thibault
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Evolution ◽  
Photosystem I ◽  
Action Spectrum ◽  
Photosynthetic Oxygen Evolution ◽  
Yellow Leaf ◽  
Wild Type ◽  
In The Wild ◽  
Aurea Mutant ◽  
Yellow Pigments

Abstract Protoplasts prepared from the wild type tobacco N. tabacum var. John William’s Broadleaf exhibit photosynthetic oxygen-evolution if the suspension medium is supplemented with bicarbonate. In the absence of bicarbonate no steady state oxygen-evolution is observed with such preparations. Instead, an appreciable uptake which is mainly insensitive to DCMU and which persists over hours, and therefore is no induction phenomenon, is seen. Protoplasts of the tobacco aurea mutant Su/su, which is a plant with an exceptionally high photorespiration, show an oxygen consumption in the light which is 4 to 5 times higher per protoplast than in the wild type. Again, the uptake is practically insensitive to DCMU which means that the effect is to be associated with photosystem I. This is further substantiated by the fact that protoplasts prepared from yellow leaf1 sec­tions of the variegated tobacco mutant NC 95 also show the light induced uptake. As reported earlier, the yellow leaf sections of this mutant exhibit only photosystem I reactions.The action spectrum for this oxygen-uptake yields the spectrum of chlorophyll. Consequently, this uptake is an inherent property of the chloroplast and has nothing to do with earlier described, light-dependent oxygen consumptions, which were mainly driven by blue light and hence used some yellow pigment as the photoreceptor. No effect or contribution of yellow pigments such as carotenoids is seen since the action spectrum with the yellow tobacco mutants which have an up to 4 fold higher carotenoid/chlorophyll ratio than the wild type is identical to that of the wild type.

Chloride Requirement for Oxygen Evolution in Photosynthesis

1963 ◽  
Vol 18 (9) ◽  
pp. 683-688 ◽  
Author(s):  
J. M. Bové ◽  
Colette Bové ◽  
F. R. Whatley ◽  
Daniel I. Arnon
Keyword(s):  
Oxygen Evolution ◽  
Photochemical Reactions ◽  
Photosynthetic Oxygen Evolution ◽  
Ferricyanide Reduction ◽  
Atp Formation ◽  
Cyclic Photophosphorylation ◽  
Photosynthetic Oxygen ◽  
Isolated Chloroplasts ◽  
Spinach Leaves

The role of chloride in photosynthetic oxygen evolution was reinvestigated by determining the effect of this ion on photochemical reactions of chloroplasts in which oxygen either is or is not produced. The chloroplasts used were isolated from normal spinach leaves. The level of chloride in the reaction mixture was controlled by washing the isolated chloroplasts and by avoiding a chloride contamination from the water and chemicals used. Chloride was found to be essential for each of the photochemical reactions of chloroplasts in which oxygen is produced. These included (a) photoreduction of TPN, (b) photophosphorylation of the noncyclic type in which TPN or ferricyanide reduction is coupled with ATP formation and (c) photophosphorylation of the aerobic, “pseudocyclic” type in which oxygen production occurs but is masked by an equal oxygen consumption. No chloride requirement was found for the anaerobic, cyclic photophosphorylation in which oxygen is not produced. These results support the view that chloride is an essential cofactor for oxygen evolution in photosynthesis.

scholarly journals The Action Spectrum of Photosynthesis in Euglena Gracilis at Different Stages of Chloroplast Development

1970 ◽  
Vol 23 (1) ◽  
pp. 33 ◽  
Author(s):  
JT O Kirk ◽  
JA Reade
Keyword(s):  
Oxygen Evolution ◽  
Euglena Gracilis ◽  
Chloroplast Development ◽  
Platinum Electrode ◽  
Action Spectrum ◽  
Thin Strip ◽  
Agarose Gel ◽  
Photosynthetic Oxygen Evolution ◽  
Unicellular Algae ◽  
Photosynthetic Oxygen

A method for measuring the action spectra of photosynthetic oxygen evolution in unicellular algae is described. This involves embedding the cells in a thin strip of agarose gel. These gel strips can then be used for action spectrum measurements, with a bare platinum electrode of the Haxo and Blinks type in the same way as measure� ments are made with a piece of multicellular algal thallus.

Evidence for a Rapid Oxygen-Uptake in Tobacco Chloroplasts

1979 ◽  
Vol 34 (5-6) ◽  
pp. 414-418 ◽  
Author(s):  
Georg H. Schmid ◽  
Pierre Thibault
Keyword(s):  
Oxygen Uptake ◽  
Photosystem I ◽  
Photosynthetic Oxygen Evolution ◽  
Wild Type ◽  
Intact Chloroplasts ◽  
Chlorophyll Mutants ◽  
Photosynthetic Oxygen ◽  
Aurea Mutant ◽  
Oxygen Yield ◽  
Fully Functioning

Abstract A fast oxygen uptake, induced by a sequence of short (5 µsec) saturating flashes was observed in chloroplasts of wild type tobacco and two chlorophyll-deficient tobacco mutants. One of the chlorophyll mutants is the earlier described variegated tobacco NC 95. Chloroplasts of this mutant exhibit only photosystem I mediated photoreactions, hence the observed oxygen uptake is to be associated with photosystem I. This is further substantiated by the fact that the oxygen uptake is insensitive to DCMU in the two chloroplast types used, which have both photosystems fully functioning. The uptake depends on the addition of electron acceptors like p-benzoquinone in intact chloroplasts or on p-benzoquinone or ferricyanide in chloroplasts that have lost the envelope. In dark adapted chloroplasts, therefore, under these conditions the overall apparent gas exchange in the first two flashes is consumption. Although the uptake is slower than photosynthetic oxygen evolution it clearly affects the oxygen yield in the flash sequences. This is demonstrated by several experiments in which the apparent oxygen consumption in the absence of DCMU oscillates with a periodicity of four. We have indications that in chloroplasts of the tobacco aurea mutant Su/su the oxygen uptake is faster than in wild type chloroplasts.

scholarly journals TIP family aquaporins play role in chloroplast osmoregulation and photosynthesis

2020 ◽  
Author(s):  
Azeez Beebo ◽  
Ahmad Zia ◽  
Christopher R. Kinzel ◽  
Andrei Herdean ◽  
Karim Bouhidel ◽  
...  
Keyword(s):  
Electron Transport ◽  
Oxygen Evolution ◽  
Photosynthetic Electron Transport ◽  
Chloroplast Envelope ◽  
Photosynthetic Oxygen Evolution ◽  
Wild Type ◽  
Thylakoid Lumen ◽  
Photosynthetic Oxygen ◽  
Osmotic Treatment ◽  
Envelope Membranes

SUMMARYPhotosynthetic oxygen evolution by photosystem II requires water supply into the chloroplast to reach the thylakoid lumen. A rapid water flow is also required into the chloroplast for optimal oxygen evolution and to overcome osmotic stress. The mechanisms governing water transport in chloroplasts are largely unexplored. Previous proteomics indicated the presence of three aquaporins from the tonoplast intrinsic protein (TIP) family, TIP1;1, TIP1;2 and TIP2;1, in chloroplast membranes of Arabidopsis thaliana. Here we revisited their location and studied their role in chloroplasts. Localization experiments indicated that TIP2;1 resides in the thylakoid, whereas TIP1;2 is present in both thylakoid and envelope membranes. Mutants lacking TIP1;2 and/or TIP2;1 did not display a macroscopic phenotype when grown under standard conditions. The mutant chloroplasts and thylakoids underwent less volume changes than the corresponding wild type preparations upon osmotic treatment and in the light. Significantly reduced rates of photosynthetic electron transport were obtained in the mutant leaves, with implications on the CO2 fixation rates. However, electron transport rates did not significantly differ between mutants and wild type when isolated thylakoids were examined. Less acidification of the thylakoid lumen was measured in mutants thylakoids, resulting in a slower induction of delta pH-dependent photoprotective mechanisms. These results identify TIP1;2 and TIP2;1 as chloroplast proteins and highlight their importance for osmoregulation and optimal photosynthesis. A third aquaporin, TIP1;1, is present in the chloroplast envelope, and may play role in photosynthesis under excessive light conditions, as based on the weak photosynthetic phenotype of its mutant.

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