scholarly journals Salt Priming Protects Photosynthetic Electron Transport against Low-Temperature-Induced Damage in Wheat

Sensors ◽  
2019 ◽  
Vol 20 (1) ◽  
pp. 62 ◽  
Author(s):  
Hui Li ◽  
Huawei Li ◽  
Yanjie Lv ◽  
Yongjun Wang ◽  
Zongshuai Wang ◽  
...  
Keyword(s):  
Electron Transport ◽  
Low Temperature ◽  
Reaction Center ◽  
Early Stage ◽  
Photochemical Efficiency ◽  
Photosynthetic Electron Transport ◽  
Nacl Solution ◽  
Wheat Seedlings ◽  
Germinating Seeds ◽  
Salt Priming

Low temperature limits the photochemical efficiency of photosystems in wheat plants. To test the effect of salt priming on the photosynthetic electron transport in wheat under low temperature, the germinating seeds of a winter wheat cv. Jimai44 were primed with varying concentrations of NaCl solutions (0, 10, 30, and 50 mM NaCl, indicated by S0, S10, S30, and S50, respectively) for 6 d, and after 11 d of recovery, the seedlings were subsequently exposed to 24-h low-temperature stress (2 °C). Under low temperature, the S30 plants possessed the highest absorption flux per reaction center and higher density of reaction center per cross-section among the treatments. In addition, S30 plants had higher trapped energy flux for reducing QA and fraction of QA-reducing reaction centers and non-QB reducing center than the non-primed plants under low temperature, indicating that S30 plants could maintain the energy balance of photosystems and a relatively higher maximum quantum efficiency of photosystem II under low temperature. In addition, the low temperature-induced MDA accumulation and cell death were alleviated by salt priming in S30 plants. It was suggested that salt priming with an optimal concentration of NaCl solution (30 mM) during seed germination enhanced the photochemical efficiency of photosystems in wheat seedlings, which could be a potential approach to improve cold tolerance in wheat at an early stage.

scholarly journals Irradiance and nutrient-dependent effects on photosynthetic electron transport in Arctic phytoplankton: A comparison of two chlorophyll fluorescence-based approaches to derive primary photochemistry

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0256410
Author(s):  
Yayla Sezginer ◽  
David J. Suggett ◽  
Robert W. Izett ◽  
Philippe D. Tortell
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Electron Transport Rate ◽  
Photochemical Efficiency ◽  
Photosynthetic Electron Transport ◽  
Marine Phytoplankton ◽  
Transport Rate ◽  
Variable Fluorescence ◽  
Primary Photochemistry ◽  
Electron Transport Rates

We employed Fast Repetition Rate fluorometry for high-resolution mapping of marine phytoplankton photophysiology and primary photochemistry in the Lancaster Sound and Barrow Strait regions of the Canadian Arctic Archipelago in the summer of 2019. Continuous ship-board analysis of chlorophyll a variable fluorescence demonstrated relatively low photochemical efficiency over most of the cruise-track, with the exception of localized regions within Barrow Strait, where there was increased vertical mixing and proximity to land-based nutrient sources. Along the full transect, we observed strong non-photochemical quenching of chlorophyll fluorescence, with relaxation times longer than the 5-minute period used for dark acclimation. Such long-term quenching effects complicate continuous underway acquisition of fluorescence amplitude-based estimates of photosynthetic electron transport rates, which rely on dark acclimation of samples. As an alternative, we employed a new algorithm to derive electron transport rates based on analysis of fluorescence relaxation kinetics, which does not require dark acclimation. Direct comparison of kinetics- and amplitude-based electron transport rate measurements demonstrated that kinetic-based estimates were, on average, 2-fold higher than amplitude-based values. The magnitude of decoupling between the two electron transport rate estimates increased in association with photophysiological diagnostics of nutrient stress. Discrepancies between electron transport rate estimates likely resulted from the use of different photophysiological parameters to derive the kinetics- and amplitude-based algorithms, and choice of numerical model used to fit variable fluorescence curves and analyze fluorescence kinetics under actinic light. Our results highlight environmental and methodological influences on fluorescence-based photochemistry estimates, and prompt discussion of best-practices for future underway fluorescence-based efforts to monitor phytoplankton photosynthesis.

scholarly journals Relationship between CO2 Assimilation, Photosynthetic Electron Transport, and Active O2 Metabolism in Leaves of Maize in the Field during Periods of Low Temperature

1998 ◽  
Vol 116 (2) ◽  
pp. 571-580 ◽  
Author(s):  
Michael J. Fryer ◽  
James R. Andrews ◽  
Kevin Oxborough ◽  
David A. Blowers ◽  
Neil R. Baker
Keyword(s):  
Electron Transport ◽  
Low Temperature ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation

Hydroxyl radicals are not the protagonists of UV-B-induced damage in isolated thylakoid membranes

2007 ◽  
Vol 34 (12) ◽  
pp. 1112 ◽  
Author(s):  
Iva Šnyrychová ◽  
Péter B. Kós ◽  
Éva Hideg
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transport ◽  
Hydroxyl Radicals ◽  
Early Stage ◽  
D1 Protein ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Oxygen Species ◽  
Free Hydrogen ◽  
By Products

The production of reactive oxygen species (ROS) was studied in isolated thylakoid membranes exposed to 312 nm UV-B irradiation. Hydroxyl radicals (•OH) and hydrogen peroxide were measured directly, using a newly developed method based on hydroxylation of terephthalic acid and the homovanillic acid/peroxidase assay, respectively. At the early stage of UV-B stress (doses lower than 2.0 J cm–2), •OH were derived from superoxide radicals via hydrogen peroxide. Production of these ROS was dependent on photosynthetic electron transport and was not exclusive to UV-B. Both ROS were found in samples exposed to the same doses of PAR, suggesting that the observed ROS are by-products of the UV-B-driven electron transport rather than specific initiators of the UV-B-induced damage. After longer exposure of thylakoids to UV-B, leading to the inactivation of PSII centres, a small amount of •OH was still observed in thylakoids, even though no free hydrogen peroxide was detected. At this late stage of UV-B stress, •OH may also be formed by the direct cleavage of organic peroxides by UV-B. Immunodetection showed that the presence of the observed ROS alone was not sufficient to achieve the degradation of the D1 protein of PSII centres.

The Leafless Orchid Cymbidium macrorhizon Performs Photosynthesis in the Pericarp during the Fruiting Season

2021 ◽  
Author(s):  
Koichi Kobayashi ◽  
Kenji Suetsugu ◽  
Hajime Wada
Keyword(s):  
Electron Transport ◽  
Mycorrhizal Fungi ◽  
Significant Proportion ◽  
Photochemical Efficiency ◽  
Fluorescence Analysis ◽  
Photosynthetic Electron Transport ◽  
Isotopic Analysis ◽  
Fluorescence Induction ◽  
Induction Kinetics ◽  
Chl Fluorescence

Abstract Photosynthesis with highly photoreactive chlorophyll (Chl) provides energy for plant growth but with simultaneous risk of photooxidative damage and photoprotection costs. Although the leafless orchid Cymbidium macrorhizon mostly depends on mycorrhizal fungi for carbon, it accumulates Chl particularly during fruiting and may not be fully mycoheterotrophic. In fact, stable isotopic analysis suggested that the fruiting C. macrorhizon specimens obtain a significant proportion of its carbon demands through photosynthesis. However, actual photosynthetic characteristics of this leafless orchid are unknown. To reveal the functionality of photosynthetic electron transport in C. macrorhizon, we compared its photosynthetic properties with those of its relative mixotrophic orchid Cymbidium goeringii and the model plant Arabidopsis thaliana. Compared with C. goeringii and A. thaliana, maximum photochemical efficiency of PSII was substantially low in C. macrorhizon. Chl fluorescence induction kinetics revealed that the electron transport capacity of PSII was limited in C. macrorhizon. Chl fluorescence analysis at 77 K suggested partial energetic disconnection of the light-harvesting antenna from the PSII reaction center in C. macrorhizon. Despite its low PSII photochemical efficiency, C. macrorhizon showed photosynthetic electron transport activity both in the field and under laboratory conditions. Cymbidium macrorhizon developed strong nonphotochemical quenching in response to increased light intensity as did C. goeringii, suggesting the functionality of photoprotective systems in this orchid. Moreover, C. macrorhizon fruit developed stomata on the pericarp and showed net O2-evolving activity. Our data demonstrate that C. macrorhizon can perform photosynthetic electron transport in the pericarp, although its contribution to net carbon acquisition may be limited.

scholarly journals Responses of the Photosynthetic Electron Transport Reactions Stimulate the Oxidation of the Reaction Center Chlorophyll of Photosystem I, P700, under Drought and High Temperatures in Rice

2019 ◽  
Vol 20 (9) ◽  
pp. 2068 ◽  
Author(s):  
Shinya Wada ◽  
Daisuke Takagi ◽  
Chikahiro Miyake ◽  
Amane Makino ◽  
Yuji Suzuki
Keyword(s):  
Drought Stress ◽  
Electron Transport ◽  
Reaction Center ◽  
High Temperatures ◽  
Photosystem I ◽  
Stress Responses ◽  
Oryza Sativa L ◽  
Photosynthetic Electron Transport ◽  
Temperature Regimes ◽  
Underlying Mechanisms

It is of interest how photosynthetic electron transport (PET) reactions respond to excess light energy caused by the combination of drought stress and high temperatures. Since such information is scarcely available for photosystem I (PSI), this question was explored in rice (Oryza sativa L.) plants subjected to drought stress, using culture solutions that contain poly(ethylene glycol) at different concentrations under two day/night temperature regimes. At 27/22 °C (day/night), drought stress led to the oxidation of the reaction center of the chlorophyll of PSI (P700), and also led to decreases in the quantum efficiencies of photosystem II (PSII) and PSI, and a reduction of the primary quinone electron acceptor of PSI. Such drought stress responses were wholly stimulated at 35/30 °C. These parameters were strongly correlated with each other and were minimally affected by temperature. These results indicate that the drought stress responses of the respective PET reactions are closely associated with each other in the oxidization of P700 and that such responses are stimulated at high temperatures. The underlying mechanisms of these phenomena were discussed. While P700 oxidation is thought to suppress reactive oxygen species (ROS) production, PSI photoinhibition was observed under severe stress conditions, implying that P700 oxidation is not sufficient for the protection of PSI under drought stress.

scholarly journals Chlorophyll fluorescence-based estimates of photosynthetic electron transport in Arctic phytoplankton assemblages

2021 ◽  
Author(s):  
Yayla Sezginer ◽  
David J. Suggett ◽  
Robert W. Izett ◽  
Philippe D. Tortell
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Electron Transport Rate ◽  
Photochemical Efficiency ◽  
Photosynthetic Electron Transport ◽  
Marine Phytoplankton ◽  
Transport Rate ◽  
Photochemical Quenching ◽  
Variable Fluorescence ◽  
Electron Transport Rates

AbstractWe employed Fast Repetition Rate fluorometry for high-resolution mapping of marine phytoplankton photophysiology and primary productivity in the Lancaster Sound and Barrow Strait regions of the Canadian Arctic Archipelago in the summer of 2019. Continuous ship-board analysis of chlorophyll a variable fluorescence demonstrated relatively low photochemical efficiency over most of the cruise-track, with the exception of localized regions within Barrow Strait where there was increased vertical mixing and proximity to land-based nutrient sources. Along the full transect, we observed strong non-photochemical quenching of chlorophyll fluorescence, with relaxation times longer than the 5-minute period used for dark acclimation. Such long-term quenching effects complicate continuous underway acquisition of fluorescence amplitude-based estimates of photosynthetic electron transport rates, which rely on dark acclimation of samples. As an alternative, we employed a new algorithm to derive electron transport rates based on analysis of fluorescence relaxation kinetics, which does not require dark acclimation. Direct comparison of kinetics- and amplitude-based electron transport rate measurements demonstrated kinetic-based estimates were, on average, 2-fold higher than amplitude-based values. The magnitude of decoupling between the two electron transport rate estimates increased in association with photophysiological diagnostics of nutrient stress. Discrepancies between electron transport rate estimates likely resulted from the use of different photophysiological parameters to derive the kinetics- and amplitude-based algorithms, and choice of numerical model used to fit variable fluorescence curves and analyze fluorescence kinetics under actinic light. Our results highlight environmental and methodological influences on fluorescence-based productivity estimates, and prompt discussion of best-practices for future underway fluorescence-based efforts to monitor phytoplankton photosynthesis.

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