scholarly journals Ascorbate biosynthesis and function in photoprotection

2000 ◽  
Vol 355 (1402) ◽  
pp. 1455-1464 ◽  
Author(s):  
Nicholas Smirnoff
Keyword(s):  
Active Oxygen Species ◽  
Electron Flow ◽  
High Light Intensity ◽  
High Light ◽  
Pool Size ◽  
Ultraviolet B ◽  
Photochemical Quenching ◽  
Inner Mitochondrial Membrane ◽  
Oxidative Stresses ◽  
High Concentrations

Ascorbate (vitamin C) can reach very high concentrations in chloroplasts (20–300 mM).The pool size in leaves and chloroplasts increases during acclimation to high light intensity and the highest concentrations recorded are in high alpine plants. Multiple functions for ascorbate in photosynthesis have been proposed, including scavenging of active oxygen species generated by oxygen photoreduction and photorespiration, regeneration of α–tocopherol from α–tocopheryl radicals, cofactor for violaxanthin de–epoxidase and donation of electrons to photosystem II. Hydrogen peroxide scavenging is catalysed by ascorbate peroxidase (Mehler peroxidase reaction) and the subsequent regeneration of ascorbate by reductant derived from photosystem I allows electron flow in addition to that used for CO 2 assimilation. Ascorbate is synthesized from guanosine diphosphate–mannose via L–galactose and L–galactono–1,4–lactone. The last step, catalysed by L–galactono–1,4–lactone dehydrogenase, is located on the inner mitochondrial membrane and uses cytochrome c as electron acceptor. L–galactono–1,4–lactone oxidation to ascorbate by intact leaves is faster in high–light acclimated leaves and is also enhanced by high light, suggesting that this step contributes to the control of pool size by light. Ascorbate–deficient Arabidopsis thaliana vtc mutants are hypersensitive to a number of oxidative stresses including ozone and ultraviolet B radiation. Further investigation of these mutants shows that they have reduced zeaxanthin–dependent non–photochemical quenching, confirming that ascorbate is the cofactor for violaxanthin de–epoxidase and that availability of thylakoid lumen ascorbate could limit this reaction. The vtc mutants are also more sensitive to photooxidation imposed by combined high light and salt treatments.

Acquired tolerance of the photosynthetic apparatus to photoinhibition as a result of growing Solanum lycopersicum at moderately higher temperature and light intensity

2019 ◽  
Vol 46 (6) ◽  
pp. 555 ◽  
Author(s):  
Milena T. Gerganova ◽  
Aygyun K. Faik ◽  
Maya Y. Velitchkova
Keyword(s):  
High Temperature ◽  
Quantum Yield ◽  
Light Intensity ◽  
Electron Flow ◽  
Photosynthetic Apparatus ◽  
High Light ◽  
Cyclic Electron Flow ◽  
Photochemical Quenching ◽  
Kinetics Of ◽  
Moderately High Temperature

The kinetics of photoinhibition in detached leaves from tomato plants (Solanium lycopersicum L. cv. M82) grown for 6 days under different combinations of optimal and moderately high temperature and optimal and high light intensity were studied. The inhibition of PSII was evaluated by changes in maximal quantum yield, the coefficient of photochemical quenching and the quantum yield of PSII. The changes of PSI activity was estimated by the redox state of P700. The involvement of different possible protective processes was checked by determination of nonphotochemical quenching and cyclic electron flow around PSI. To evaluate to what extent the photosynthetic apparatus and its response to high light treatment was affected by growth conditions, the kinetics of photoinhibition in isolated thylakoid membranes were also studied. The photochemical activities of both photosystems and changes in the energy distribution and interactions between them were evaluated by means of a Clark electrode and 77 K fluorescence analysis. The data showed an increased tolerance to photoinhibition in plants grown under a combination of moderately high temperature and light intensity, which was related to the stimulation of cyclic electron flow, PSI activity and rearrangements of pigment–protein complexes, leading to a decrease in the excitation energy delivered to PSII.

scholarly journals Experimental researches on vegetable assimilation and respiration. XVIII.—The relation between stomatal opening and assimilation.—A critical study of assimilation rates and porometer rates in leaves of Cherry Laurel

1928 ◽  
Vol 102 (720) ◽  
pp. 488-533 ◽  
Keyword(s):  
Light Intensity ◽  
Diurnal Rhythm ◽  
High Light Intensity ◽  
High Light ◽  
Stomatal Opening ◽  
Critical Study ◽  
Assimilation Rate ◽  
High Concentrations ◽  
Experimental Researches ◽  
Cherry Laurel

In a previous communication it was shown that there is, in Cherry Laurel leaves, at “limiting” concentrations of CO 2 , a marked diurnal rhythm of apparent assimilation. In spite of the maintenance of a constant high light intensity, the assimilation rate falls to very low values during the night but rises again in the morning. At high concentrations of CO 2 , such that light, instead of CO 2 , is limiting the rate, there is no diurnal rhythm, the light limited value of assimilation being steadily maintained for more than 24 hours. There is, in addition to the diurnal rhythm, a seasonal rhythm of assimilation—the pitch or level of the diurnal assimilation curves being higher in November than in July, August and September. Also the level of assimilation, for a given “limiting” concentration of CO 2 , is higher at high light intensity than at low. It was suggested that these variations in assimilation were largely due to variations in stomatal opening. The work on porometer rates and assimilation rates described in the present paper was undertaken in order to test this hypothesis and to explore, as far as was possible by such means, the relation between stomatal opening and assimilation rate.

scholarly journals An optimised method for correcting quenched fluorescence yield

2014 ◽  
Vol 11 (3) ◽  
pp. 1243-1264 ◽  
Author(s):  
L. Biermann ◽  
C. Guinet ◽  
M. Bester ◽  
A. Brierley ◽  
L. Boehme
Keyword(s):  
Light Intensity ◽  
Southern Ocean ◽  
Fluorescence Emission ◽  
Euphotic Zone ◽  
Fluorescence Yield ◽  
High Light Intensity ◽  
High Light ◽  
Photochemical Quenching ◽  
Non Photochemical Quenching

Abstract. Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. Previously, this has been done using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, the assumption of homogeneity is not robust in oceanic regimes that support deep chlorophyll maxima. To account for these features, we correct from the limit of the euphotic zone, defined as the depth at which light is at ~1% of the surface value. This method was applied to fluorescence data collected by eleven animal-borne fluorometers deployed in the Southern Ocean over four austral summers. Six tags returned data showing evidence of deep chlorophyll features. Using the depth of the euphotic layer, quenching was corrected without masking subsurface fluorescence signals.

scholarly journals Roles of OsSOQ1 in photoprotection and fatty acid metabolism of rice

2021 ◽  
Author(s):  
Zhen-Hui Kang ◽  
Yang Gou ◽  
Qi-Rui Deng ◽  
Zi-yu Hu ◽  
Guan-Rong Li
Keyword(s):  
Fatty Acid ◽  
Light Intensity ◽  
Fatty Acid Metabolism ◽  
Acid Metabolism ◽  
Function Analysis ◽  
Photochemical Efficiency ◽  
High Light Intensity ◽  
High Light ◽  
Redox Activity ◽  
Photochemical Quenching

Abstract Presented here is the function analysis of a homolog of Arabidopsis SOQ1, OsSOQ1 in rice. Homozygous mutants (ossoq1) were obtained by CRISPR/Cas9 to knockout OsSOQ1. The mutants showed significant lower plant height, tiller number, panicle length, effective panicle, and grain number per panicle compared to the wild-type (WT). Western blot analysis showed that OsSOQ1 is a thylakoid membrane protein, with the thioredoxin-like (Trx-like) domain facing the lumen. Loss of OsSOQ1 did not significantly affect the protein level of photosystem II (PSII) subunits, but down-regulated the content of a non-photochemical quenching (NPQ) player PsbS, resulting in a low NPQ under high light intensity in the mutant. UPLC-MS/MS experiments showed that OsSOQ1 is involved in the fatty acid biosynthesis pathway of rice. The Trx-like domain possessed redox activity in vitro as shown by insulin assay; and in the yeast two-hybrid experiment, it was found that the Trx-like domain interacted with the chloroplast lipocalin OsLCNP, which usually binds lipid molecules. These findings revealed that the role of OsSOQ1 is to maintain the photochemical efficiency of PSII under high light intensity and regulate fatty acid metabolism in rice.

scholarly journals Light potentials of photosynthetic energy storage in the field: what limits the ability to use or dissipate rapidly increased light energy?

2021 ◽  
Vol 8 (12) ◽  
Author(s):  
Atsuko Kanazawa ◽  
Abhijnan Chattopadhyay ◽  
Sebastian Kuhlgert ◽  
Hainite Tuitupou ◽  
Tapabrata Maiti ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Electron Flow ◽  
Crop Productivity ◽  
Open Science ◽  
High Light ◽  
Light Energy ◽  
Photochemical Quenching ◽  
Plant Photosynthesis ◽  
Photosynthetic Control ◽  
Non Photochemical Quenching

The responses of plant photosynthesis to rapid fluctuations in environmental conditions are critical for efficient conversion of light energy. These responses are not well-seen laboratory conditions and are difficult to probe in field environments. We demonstrate an open science approach to this problem that combines multifaceted measurements of photosynthesis and environmental conditions, and an unsupervised statistical clustering approach. In a selected set of data on mint ( Mentha sp.), we show that ‘light potentials’ for linear electron flow and non-photochemical quenching (NPQ) upon rapid light increases are strongly suppressed in leaves previously exposed to low ambient photosynthetically active radiation (PAR) or low leaf temperatures, factors that can act both independently and cooperatively. Further analyses allowed us to test specific mechanisms. With decreasing leaf temperature or PAR, limitations to photosynthesis during high light fluctuations shifted from rapidly induced NPQ to photosynthetic control of electron flow at the cytochrome b 6 f complex. At low temperatures, high light induced lumen acidification, but did not induce NPQ, leading to accumulation of reduced electron transfer intermediates, probably inducing photodamage, revealing a potential target for improving the efficiency and robustness of photosynthesis. We discuss the implications of the approach for open science efforts to understand and improve crop productivity.

scholarly journals CP12 Is Involved in Protection against High Light Intensity by Suppressing the ROS Generation in Synechococcus elongatus PCC7942

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1275
Author(s):  
Masahiro Tamoi ◽  
Shigeru Shigeoka
Keyword(s):  
Oxidative Stress ◽  
Photosynthetic Activity ◽  
Regulatory System ◽  
High Light Intensity ◽  
High Light ◽  
Ros Generation ◽  
Light Conditions ◽  
Low Light ◽  
Oxidative Stresses ◽  
Synechococcus Elongatus Pcc7942

We previously reported that CP12 formed a complex with GAPDH and PRK and regulated the activities of these enzymes and the Calvin–Benson cycle under dark conditions as the principal regulatory system in cyanobacteria. More interestingly, we found that the cyanobacterial CP12 gene-disrupted strain was more sensitive to photo-oxidative stresses such as under high light conditions and paraquat treatment. When a mutant strain that grew normally under low light was subjected to high light conditions, decreases in chlorophyll and photosynthetic activity were observed. Furthermore, a large amount of ROS was accumulated in the cells of the CP12 gene-disrupted strain. These data suggest that CP12 also functions under light conditions and may be involved in protection against oxidative stress by controlling the flow of electrons from Photosystem I to NADPH.

The role of photochemical quenching and antioxidants in photoprotection of Deschampsia antarctica

2004 ◽  
Vol 31 (7) ◽  
pp. 731 ◽  
Author(s):  
Eduardo Pérez-Torres ◽  
Andrea García ◽  
Jorge Dinamarca ◽  
Miren Alberdi ◽  
Ana Gutiérrez ◽  
...  
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Active Oxygen Species ◽  
Photochemical Efficiency ◽  
High Light ◽  
Photochemical Quenching ◽  
Deschampsia Antarctica ◽  
Oxygen Species ◽  
Excitation Light ◽  
Photochemical Efficiency Of Psii

Deschampsia antarctica Desv. (Poaceae) is the only grass that grows in the maritime Antarctic. Constant low temperatures and episodes of high light are typical conditions during the growing season at this latitude. These factors enhance the formation of active oxygen species and may cause photoinhibition. Therefore, an efficient mechanism of energy dissipation and / or scavenging of reactive oxygen species (ROS) would contribute to survival in this harsh environment. In this paper, non-acclimated and cold-acclimated D. antarctica were subjected to high light and / or low temperature for 24 h. The contribution of non-photochemical dissipation of excitation light energy and the activities of detoxifying enzymes in the development of resistance to chilling induced photoinhibition were studied by monitoring PSII fluorescence, total soluble antioxidants, and pigments contents and measuring variations in activity of superoxide dismutase (SOD; EC 1.15.1.1), ascorbate peroxidase (APX; EC 1.11.1.11), and glutathione reductase (GR; EC 1.6.4.2). The photochemical efficiency of PSII, measured as Fv / F m, and the yield of PSII electron transport (ΦPSII) both decreased under high light and low temperatures. In contrast, photochemical quenching (qP) in both non-acclimated and cold-acclimated plants remained relatively constant (approximately 0.8) in high-light-treated plants. Unexpectedly, qP was lower (0.55) in cold-acclimated plants exposed to 4°C and low light intensity. Activity of SOD in cold-acclimated plants treated with high light at low temperature showed a sharp peak 2–4 h after the beginning of the experiment. In cold-acclimated plants APX remained high with all treatments. Activity of GR decreased in cold-acclimated plants. Compared with other plants, D. antarctica exhibited high levels of SOD and APX activity. Pigment analyses show that the xanthophyll cycle is operative in this plant. We propose that photochemical quenching and particularly the high level of antioxidants help D. antarctica to resist photoinhibitory conditions. The relatively high antioxidant capacity of D. antarctica may be a determinant for its survival in the harsh Antarctic environment.

Characteristics of Photosynthesis in Different Wheat Cultivars under High Light Intensity and High Temperature Stresses

2009 ◽  
Vol 34 (12) ◽  
pp. 2196-2201 ◽  
Author(s):  
Xue-Li QI ◽  
Lin HU ◽  
Hai-Bin DONG ◽  
Lei ZHANG ◽  
Gen-Song WANG ◽  
...  
Keyword(s):  
High Temperature ◽  
Light Intensity ◽  
High Light Intensity ◽  
High Light ◽  
Wheat Cultivars ◽  
Temperature Stresses
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