scholarly journals In-depth analysis of defects in TiO2 compact electron transport layers and impact on performance and hysteresis of planar perovskite devices at low light

2020 ◽  
Vol 209 ◽  
pp. 110448
Author(s):  
Anthony Lewis ◽  
Joel R. Troughton ◽  
Benjamin Smith ◽  
James McGettrick ◽  
Tom Dunlop ◽  
...  
Keyword(s):  
Electron Transport ◽  
Low Light ◽  
Depth Analysis

Electron transport in Tradescantia leaves acclimated to high and low light: thermoluminescence, PAM-fluorometry, and EPR studies

2020 ◽  
Vol 146 (1-3) ◽  
pp. 123-141
Author(s):  
Olesya A. Kalmatskaya ◽  
Boris V. Trubitsin ◽  
Igor S. Suslichenko ◽  
Vladimir A. Karavaev ◽  
Alexander N. Tikhonov
Keyword(s):  
Electron Transport ◽  
Pam Fluorometry ◽  
Low Light

scholarly journals Symbiosis extended: exchange of photosynthetic O2 and fungal-respired CO2 mutually power metabolism of lichen symbionts

2019 ◽  
Vol 143 (3) ◽  
pp. 287-299 ◽  
Author(s):  
Marie-Claire ten Veldhuis ◽  
Gennady Ananyev ◽  
G. Charles Dismukes
Keyword(s):  
Electron Transport ◽  
Energy Conversion ◽  
Water Oxidation ◽  
Photosynthetic Electron Transport ◽  
Fluorescence Yield ◽  
Consecutive Series ◽  
Low Light ◽  
Conversion Rates ◽  
Algal Photosynthesis ◽  
Flavoparmelia Caperata

AbstractLichens are a symbiosis between a fungus and one or more photosynthetic microorganisms that enables the symbionts to thrive in places and conditions they could not compete independently. Exchanges of water and sugars between the symbionts are the established mechanisms that support lichen symbiosis. Herein, we present a new linkage between algal photosynthesis and fungal respiration in lichen Flavoparmelia caperata that extends the physiological nature of symbiotic co-dependent metabolisms, mutually boosting energy conversion rates in both symbionts. Measurements of electron transport by oximetry show that photosynthetic O2 is consumed internally by fungal respiration. At low light intensity, very low levels of O2 are released, while photosynthetic electron transport from water oxidation is normal as shown by intrinsic chlorophyll variable fluorescence yield (period-4 oscillations in flash-induced Fv/Fm). The rate of algal O2 production increases following consecutive series of illumination periods, at low and with limited saturation at high light intensities, in contrast to light saturation in free-living algae. We attribute this effect to arise from the availability of more CO2 produced by fungal respiration of photosynthetically generated sugars. We conclude that the lichen symbionts are metabolically coupled by energy conversion through exchange of terminal electron donors and acceptors used in both photosynthesis and fungal respiration. Algal sugars and O2 are consumed by the fungal symbiont, while fungal delivered CO2 is consumed by the alga.

Photoinhibitory Damage to Chloroplasts under Phosphate Deficiency and Alleviation of Deficiency and Damage by Photorespiratory Reactions

1989 ◽  
Vol 44 (5-6) ◽  
pp. 524-536 ◽  
Author(s):  
U. Heber ◽  
J. Viil ◽  
S. Neimanis ◽  
T. Mimura ◽  
K.-J. Dietz
Keyword(s):  
Electron Transport ◽  
Light Intensity ◽  
Oxygen Evolution ◽  
High Light Intensity ◽  
High Light ◽  
Phosphate Deficiency ◽  
Loss Of Function ◽  
Low Light ◽  
Chloroplast Stroma ◽  
Pi Deficiency

Abstract Effects of Pi deficiency on photosynthesis ot isolated spinach chloroplasts were examined. The following observations were made: (1) Chloroplasts isolated in Pi-free media evolved oxygen in the light in the absence of added Pi until acid-extractable Pi in the chloroplasts had decreased to 1 to 2.5 m M . This Pi was unavailable for photophosphorylation as shown by the inability of the chloroplasts to respond by oxygen evolution to the addition of PGA. In the state of Pi-deficiency, stromal ATP to A DP ratios were in the light close to or below ratios observed in the dark. In the presence of 2 mᴍ PGA, addition of 20 μm Pi was insufficient to increase ATP to ADP ratios, but sufficient for appreciable oxygen evolution. (2) More Pi was available for oxygen evolution of phosphate-deficient chloroplasts at low levels of C02 than at high levels. This was due mainly to the suppression of oxygenation of RuBP by high C02 levels which prevented formation of phosphoglycolate and the subsequent release of Pi into the chloroplast stroma. (3) More oxygen was produced by phosphate-deficient chloroplasts at a low light intensity than at a high light intensity. This was due to increased availability of endogenous Pi under low light and to photoinhibition of the chloroplasts by high light. The main product of photosynthesis of phosphate-deficient chloroplasts in the presence of a high bicarbonate concentration was starch, and the main soluble product was PGA. (4) After phosphate-deficient chloroplasts had ceased to evolve oxygen in the light, they be­ came photosensitive. Part of the loss of the capacity for oxygen evolution is attributed to leakage of PGA, but the main reason for loss of function is photoinactivation of electron transport. Both photosystems of the electron transport chain were damaged by light. (5) Protection against photoinactivation was provided by coupled electron transport. Photo­ inactivation of phosphate-deficient chloroplasts was less extensive in the presence of low C02 concentrations which permitted oxygenation of RuBP than at high CO2 concentrations. Electron transport to C02 and other physiological electron acceptors and to the herbicide methylviologen was also protective. However, electron transport to oxygen in the Mehler reaction failed to provide appreciable protection against high light intensities, because oxygen reduction is slow and reactive oxygen species produced in the light contribute to photoinactivation.

scholarly journals Photochemical Acclimation of Three Contrasting Species to Different Light Levels: Implications for Optimizing Supplemental Lighting

2017 ◽  
Vol 142 (5) ◽  
pp. 346-354 ◽  
Author(s):  
Shuyang Zhen ◽  
Marc W. van Iersel
Keyword(s):  
Electron Transport ◽  
Light Intensity ◽  
Photochemical Efficiency ◽  
Light Response ◽  
High Light ◽  
Photon Flux ◽  
Ambient Light ◽  
Response Curves ◽  
Low Light ◽  
Supplemental Lighting

Photosynthetic responses to light are dependent on light intensity, vary among species, and can be affected by acclimation to different light environments (e.g., light intensity, spectrum, and photoperiod). Understanding how these factors affect photochemistry is important for improving supplemental lighting efficiency in controlled-environment agriculture. We used chlorophyll fluorescence to determine photochemical light response curves of three horticultural crops with contrasting light requirements [sweetpotato (Ipomea batatas), lettuce (Lactuca sativa), and pothos (Epipremnum aureum)]. We also quantified how these responses were affected by acclimation to three shading treatments-full sun, 44% shade, and 75% shade. The quantum yield of photosystem II (ΦPSII), a measure of photochemical efficiency, decreased exponentially with increasing photosynthetic photon flux (PPF) in all three species. By contrast, linear electron transport rate (ETR) increased asymptotically with increasing PPF. Within each shading level, the high-light-adapted species sweetpotato used high light more efficiently for electron transport than light-intermediate lettuce and shade-tolerant pothos. Within a species, plants acclimated to high light (full sun) tended to have higher ΦPSII and ETR than those acclimated to low light (44% or 75% shade). Nonphotochemical quenching (NPQ) (an indicator of the amount of absorbed light energy that is dissipated as heat) was upregulated with increasing PPF; faster upregulation was observed in pothos as well as in plants grown under 75% shade. Our results have implications for supplemental lighting: supplemental light is used more efficiently and results in a greater increase in ETR when provided at low ambient PPF. In addition, high-light-adapted crops and crops grown under relatively high ambient light can use supplemental light more efficiently than low-light-adapted crops or those grown under low ambient light.

Light and Heat Stress Adaptation of the Symbionts of Temperate and Coral Reef Foraminifers Probed in Hospite by the Chlorophyll a Fluorescence Kinetics

1999 ◽  
Vol 54 (9-10) ◽  
pp. 671-680 ◽  
Author(s):  
Merope Tsimilli-Michael ◽  
Martin Pêcheux ◽  
Reto J. Strasser
Keyword(s):  
Heat Stress ◽  
Coral Reef ◽  
Electron Transport ◽  
Light Stress ◽  
Red Light ◽  
Low Light ◽  
Regulatory Changes ◽  
Electron Transport Activity ◽  
Response To Stress ◽  
Fluorescence Transients

Since the early 80’s massive bleaching affects the reef ecosystem. It involves, besides corals, several other species among which large foraminifers, and it corresponds to the loss of their photosynthetic symbionts or the symbionts’ pigments. The cause is unclear, though temperature elevation and strong irradiation have been considered to be primary factors. In this work we investigated in two genera of coral reef foraminifers (Amphistegina lobifera and Amphisorus heimprichii) and in the temperate foraminifer Sorites variabilis the response of photosystem II (PSII) of their symbionts in hospite upon light stress (white light of 550 μE m-2 s-1 and red light of 3200 |μE m-2 s-1) and heat stress (up to 32 °C), by means of the Chla fluorescence transients O-J-I-P they exhibit upon illumination. The transients were analysed according to the JIP-test which leads to the calculation of several structural and functional parameters providing a quantification of PSII behaviour. We observed that the various parameters undergo modifications that differ concerning both their extent and their degree of elasticity, thus indicating that different adaptive strategies are employed in response to stress. The most pronounced of these regulatory changes is a wide decrease of the quantum yield of electron transport. However, the extent of the changes, different for the three studied species, was in general smaller when the cultures were kept under low light (70 μE m-2 s-1) than in darkness. By the applied stressors, PSII was not damaged and, except for some cells in which an expulsion of symbionts was initiated, no bleaching was observed. This can be well correlated with the observed adaptability of PSII. As a working hypothesis, it is proposed that the decrease of the capacity for electron transport activity might be among the factors triggering bleaching in the field

Monte Carlo simulation of electron transport in low-light-level image intensifier

Optik ◽  
2015 ◽  
Vol 126 (2) ◽  
pp. 219-222 ◽  
Author(s):  
Lei Yan ◽  
Feng Shi ◽  
Hongchang Cheng ◽  
Yaojin Cheng ◽  
Zhipeng Hou ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Electron Transport ◽  
Image Intensifier ◽  
Light Level ◽  
Low Light

scholarly journals Absence of a common intermediate pool among individual enzyme chains of the energy-conservation pathway in chloroplasts of Euglena gracilis

1970 ◽  
Vol 116 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Joseph S. Kahn
Keyword(s):  
Electron Transport ◽  
Kinetic Model ◽  
Energy Conservation ◽  
Electron Acceptor ◽  
Specific Inhibitor ◽  
Atp Synthesis ◽  
Low Light ◽  
Cytochrome C552 ◽  
Limited Degree ◽  
Individual Enzyme

Tri-n-butyltin chloride is a specific inhibitor that binds stoicheiometrically and irreversibly with the ATP-synthesizing sites of chloroplasts. Titration of Euglena chloroplasts with tri-n-butyltin chloride shows about six ATP-synthesizing sites per molecule of cytochrome c552 or per 380 molecules of chlorophyll. This system was used to study the possibility of linkage between individual enzyme chains of the energy-conservation pathway or the possible existence of a common pool of an intermediate in this pathway. The inhibition of ATP synthesis by tri-n-butyltin chloride at low rates of electron transport (low light-intensities, NADP+ or ferricyanide as electron acceptor) agrees with a kinetic model of two to four ATP-synthesizing sites per energy-conservation chain. At high rates of electron transport, however, the results occasionally agree with a model of 20 or more sites per chain. The results are interpreted as indicating the absence of a common intermediate pool, but the presence of a limited degree of linkage between individual chains. It also indicates the presence of two energy-conservation sites in these chloroplasts.

scholarly journals Photosystem I cyclic electron flow via chloroplast NADH dehydrogenase-like complex performs a physiological role for photosynthesis at low light

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Wataru Yamori ◽  
Toshiharu Shikanai ◽  
Amane Makino
Keyword(s):  
Electron Transport ◽  
Light Intensity ◽  
Photosystem I ◽  
Nadh Dehydrogenase ◽  
Physiological Function ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Cyclic Electron Transport ◽  
Low Light ◽  
Ps I

Abstract Cyclic electron transport around photosystem I (PS I) was discovered more than a half-century ago and two pathways have been identified in angiosperms. Although substantial progress has been made in understanding the structure of the chloroplast NADH dehydrogenase-like (NDH) complex, which mediates one route of the cyclic electron transport pathways, its physiological function is not well understood. Most studies focused on the role of the NDH-dependent PS I cyclic electron transport in alleviation of oxidative damage in strong light. In contrast, here it is shown that impairment of NDH-dependent cyclic electron flow in rice specifically causes a reduction in the electron transport rate through PS I (ETR I) at low light intensity with a concomitant reduction in CO2 assimilation rate, plant biomass and importantly, grain production. There was no effect on PS II function at low or high light intensity. We propose a significant physiological function for the chloroplast NDH at low light intensities commonly experienced during the reproductive and ripening stages of rice cultivation that have adverse effects crop yield.

scholarly journals Resolving leaf level metabolism of C4Setaria viridis acclimated to low light through a biochemical model

2021 ◽  
Author(s):  
Chandra Bellasio ◽  
Maria Ermakova
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Crop Improvement ◽  
Reaction Rates ◽  
Crop Productivity ◽  
Transport Processes ◽  
Low Light ◽  
Atp Production ◽  
Biochemical Model ◽  
Leaf Level

When C4 plants are exposed to low light, CO2 concentration in the bundle sheath (BS) decreases, causing an increase in photorespiration, leakiness (the ratio of CO2 leak rate out of the BS over the rate of supply via C4 acid decarboxylation), and a consequent reduction in biochemical efficiency. This can to some extent be mitigated by complex acclimation syndromes, which are of primary importance for crop productivity, but not well studied. We unveil a strategy of leaf-level low light acclimation involving regulation of electron transport processes. Firstly, we characterise anatomy, gas-exchange and electron transport of Setaria viridis grown under low light. Through a newly developed biochemical model we resolve the photon fluxes, and reaction rates to explain how these concerted acclimation strategies sustain photosynthetic efficiency. Smaller BS in low light-grown plants limited leakiness but sacrificed light harvesting and ATP production. To counter ATP shortage and maintain high assimilation rates, plants facilitated light penetration through mesophyll and upregulated cyclic electron flow in the BS. This novel shade tolerance mechanism based on optimisation of light reactions is more efficient than the known mechanisms involving the rearrangement of dark reactions and can potentially lead to innovative strategies for crop improvement.

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