scholarly journals Oxygenic photosynthesis: EPR study of photosynthetic electron transport and oxygen-exchange, an overview

2018 ◽  
Vol 77 (1) ◽  
pp. 47-59 ◽  
Author(s):  
Alexander N. Tikhonov ◽  
Witold K. Subczynski
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Oxygen Exchange ◽  
Oxygenic Photosynthesis

scholarly journals Physiological Roles of Flavodiiron Proteins and Photorespiration in the Liverwort Marchantia polymorpha

2021 ◽  
Vol 12 ◽  
Author(s):  
Ginga Shimakawa ◽  
Hitomi Hanawa ◽  
Shinya Wada ◽  
Guy T. Hanke ◽  
Yusuke Matsuda ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Land Plant ◽  
Oxygenic Photosynthesis ◽  
Marchantia Polymorpha ◽  
Effective Quantum Yield ◽  
Electrochromic Shift ◽  
Partial Pressures ◽  
Shift Analysis ◽  
Electron Sink

Against the potential risk in oxygenic photosynthesis, that is, the generation of reactive oxygen species, photosynthetic electron transport needs to be regulated in response to environmental fluctuations. One of the most important regulations is keeping the reaction center chlorophyll (P700) of photosystem I in its oxidized form in excess light conditions. The oxidation of P700 is supported by dissipating excess electrons safely to O2, and we previously found that the molecular mechanism of the alternative electron sink is changed from flavodiiron proteins (FLV) to photorespiration in the evolutionary history from cyanobacteria to plants. However, the overall picture of the regulation of photosynthetic electron transport is still not clear in bryophytes, the evolutionary intermediates. Here, we investigated the physiological roles of FLV and photorespiration for P700 oxidation in the liverwort Marchantia polymorpha by using the mutants deficient in FLV (flv1) at different O2 partial pressures. The effective quantum yield of photosystem II significantly decreased at 2kPa O2 in flv1, indicating that photorespiration functions as the electron sink. Nevertheless, it was clear from the phenotype of flv1 that FLV was dominant for P700 oxidation in M. polymorpha. These data suggested that photorespiration has yet not replaced FLV in functioning for P700 oxidation in the basal land plant probably because of the lower contribution to lumen acidification, compared with FLV, as reflected in the results of electrochromic shift analysis.

Superoxide-and Ethane-Formation in Subchloroplast Particles: Catalysis by Pyridinium Derivatives

1980 ◽  
Vol 35 (9-10) ◽  
pp. 770-775 ◽  
Author(s):  
E. F. Elstner ◽  
H. P. Fischer ◽  
W. Osswald ◽  
G. Kwiatkowski
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Redox Potentials ◽  
Light Reaction ◽  
Pyridinium Bromide ◽  
Superoxide Formation ◽  
Fatty Acid Peroxidation ◽  
Chlorophyll Bleaching ◽  
Ethane Formation

Abstract Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E′0 values between -0 .3 8 V and -0 .6 V. Compounds of E′0 values of -0 .6 7 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide formation and ethane production independent on exogenous substrates or electron donors. The activities of these compounds decrease with decreasing redox potential, with one exception: 1-methyl-4,4′-bipyridini urn bromide with an E′0 value of lower -1 V (and thus no electron acceptor of photosystem I in chloroplast lamellae with intact electron transport) stimulates light dependent superoxide formation and unsaturated fatty acid peroxidation in sub­ chloroplast particles, maximal rates appearing after almost complete chlorophyll bleaching. Since this activity is not visible with compounds with redox potentials below -0 .6 V lacking the nitrogen atom at the 1-position of the pyridinium substituent, we assume that 1 -methyl-4,4′-bi-pyridinium bromide is “activated” by a yet unknown light reaction.

scholarly journals Effects of Different Planting Densities on Photosynthesis in Maize Determined via Prompt Fluorescence, Delayed Fluorescence and P700 Signals

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 276
Author(s):  
Wanying Chen ◽  
Bo Jia ◽  
Junyu Chen ◽  
Yujiao Feng ◽  
Yue Li ◽  
...  
Keyword(s):  
Electron Transport ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Electron Transport Chain ◽  
Plant Density ◽  
Photosynthetic Electron Transport ◽  
Planting Density ◽  
Strong Impact ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

The mutual shading among individual field-grown maize plants resulting from high planting density inevitably reduces leaf photosynthesis, while regulating the photosynthetic transport chain has a strong impact on photosynthesis. However, the effect of high planting density on the photosynthetic electron transport chain in maize currently remains unclear. In this study, we simultaneously measured prompt chlorophyll a fluorescence (PF), modulated 820 nm reflection (MR) and delayed chlorophyll a fluorescence (DF) in order to investigate the effect of high planting density on the photosynthetic electron transport chain in two maize hybrids widely grown in China. PF transients demonstrated a gradual reduction in their signal amplitude with increasing planting density. In addition, high planting density induced positive J-step and G-bands of the PF transients, reduced the values of PF parameters PIABS, RC/CSO, TRO/ABS, ETO/TRO and REO/ETO, and enhanced ABS/RC and N. MR kinetics showed an increase of their lowest point with increasing high planting density, and thus the values of MR parameters VPSI and VPSII-PSI were reduced. The shapes of DF induction and decay curves were changed by high planting density. In addition, high planting density reduced the values of DF parameters I1, I2, L1 and L2, and enhanced I2/I1. These results suggested that high planting density caused harm on multiple components of maize photosynthetic electron transport chain, including an inactivation of PSII RCs, a blocked electron transfer between QA and QB, a reduction in PSI oxidation and re-reduction activities, and an impaired PSI acceptor side. Moreover, a comparison between PSII and PSI activities demonstrated the greater effect of plant density on the former.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

Effects of Difenzoquat on Photoreactions and Respiration in Wheat (Triticum aestivum) and Wild Oat (Avena fatua)

Weed Science ◽  
1983 ◽  
Vol 31 (5) ◽  
pp. 693-699 ◽  
Author(s):  
Blaik P. Halling ◽  
Richard Behrens
Keyword(s):  
Triticum Aestivum ◽  
Electron Transport ◽  
Electron Acceptor ◽  
Photosynthetic Electron Transport ◽  
Significant Inhibition ◽  
Avena Fatua ◽  
Wild Oat ◽  
Leaf Chlorosis ◽  
Acceptor Activity ◽  
Proton Uptake

Experiments were conducted with isolated protoplasts of wild oat (Avena fatuaL. # AVEFA) and isolated chloroplasts of wild oat and wheat (Triticum aestivumL.), to determine if the methyl sulfate salt of difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) might influence photoreactions in these species. Difenzoquat did not affect CO2fixation, uncoupled electron transport, or proton uptake. At concentrations of 0.5 mM and 1 mM, difenzoquat caused a slight, but statistically significant, inhibition of photophosphorylation. Experiments assaying coupled electron transport indicated that inhibition of photophosphorylation occurred not through uncoupling, but by an energy-transfer inhibition. This same effect was observed in isolated mitocondria of both species, with about 50% inhibition of state 3 respiration rates occurring with 10 μM difenzoquat. However, no important differentials were observed in the relative susceptibilities of wheat and wild oat mitochondria. Difenzoquat also functioned as a weak autooxidizing electron acceptor in photosynthetic electron transport. Therefore, difenzoquat-induced leaf chlorosis and necrosis may result from a bipyridilium-type electron acceptor activity if sufficient herbicide is absorbed.

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