Excitation pressure as a measure of the sensitivity of photosystem II to photoinactivation

2010 ◽  
Vol 37 (10) ◽  
pp. 943 ◽  
Author(s):  
Dmytro Kornyeyev ◽  
Barry A. Logan ◽  
A. Scott Holaday
Keyword(s):  
Electron Transport ◽  
Uv Light ◽  
Thermal Dissipation ◽  
Oxygen Evolving Complex ◽  
Thermal Energy Dissipation ◽  
Cluster Mechanism ◽  
Oxygen Evolving ◽  
New Hypothesis ◽  
Excitation Pressure

The appearance of a new hypothesis implicating the oxygen-evolving complex as the dominant target of PSII photoinactivation (the ‘manganese cluster’ mechanism) suggests that the inactivation of PSII can be predicted on the basis of the total amount of incident photons, and challenges the role that electron transport and thermal dissipation of excitation energy play in mitigating PSII photoinactivation. This viewpoint article discusses evidence showing that minimising of the amount of energy reaching closed PSII reaction centres (i.e. the excitation pressure) is important for photoprotection. Examples are described where the parameters derived from excitation pressure correlate with the level of PSII photoinactivation, whereas the counting of incident photons does not. These examples confirm the role of electron transport and thermal energy dissipation as factors modulating PSII photoinactivation, and validate strategies that are aimed at understanding and improving PSII resistance to photoinactivation by analysis and manipulation of photoprotective processes. The authors conclude that an integrated model that incorporates various mechanisms of PSII photoinactivation and analysis of their contribution is needed. In addition, the role of UV light in naturally occurring PSII photoinactivation is evaluated. It is suggested that, when compared with visible light, the damaging effect of UV light may be limited under field conditions.

Photoinactivation of Photosynthetic Electron Transport under Anaerobic and Aerobic Conditions in Isolated Thylakoids of Spinach

1992 ◽  
Vol 47 (1-2) ◽  
pp. 63-68 ◽  
Author(s):  
Rekha Chaturvedi ◽  
M. Singh ◽  
P. V. Sane
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Oxygen Evolving Complex ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I ◽  
S2 State ◽  
The Stability ◽  
Oxygen Evolving ◽  
Spinach Thylakoids

Abstract The effect of exposure to strong white light on photosynthetic electron transport reactions of PS I and PS II were investigated in spinach thylakoids in the absence or presence of oxygen. Irrespective of the conditions used for photoinactivation, the damage to PS II was always much more than to PS I. Photoinactivation was severe under anaerobic conditions compared to that in air for the same duration. This shows that the presence of oxygen is required for prevention of photoinactivation of thylakoids. The susceptibility of water-splitting complex in photoinactivation is indicated by our data from experiments with chloride-deficient chloroplast membranes wherein it was observed that the whole chain electron transport from DPC to MV was much less photoinhibited than that from water. The data from the photoinactivation experiments with the Tris-treated thylakoids indicate another photodam age site at or near reaction centre of PS II. DCMU-protected PS II and oxygen-evolving complex from photoinactivation. DCMU protection can also be interpreted in terms of the stability of the PS II complex when it is in S2 state.

Role of Phosphatidylglycerol in Oxygen-Evolving Complex of Photosystem II

2008 ◽  
pp. 463-466 ◽  
Author(s):  
Naoki Mizusawa ◽  
Isamu Sakurai ◽  
Hisako Kubota ◽  
Hajime Wada
Keyword(s):  
Photosystem Ii ◽  
Oxygen Evolving Complex ◽  
Oxygen Evolving

Crucial Role of the Electron Transport Layer and UV Light on the Open-Circuit Voltage Loss in Inverted Organic Solar Cells

2017 ◽  
Vol 9 (39) ◽  
pp. 34131-34138 ◽  
Author(s):  
Aurélien Tournebize ◽  
Giorgio Mattana ◽  
Thérèse Gorisse ◽  
Antoine Bousquet ◽  
Guillaume Wantz ◽  
...  
Keyword(s):  
Electron Transport ◽  
Organic Solar Cells ◽  
Crucial Role ◽  
Open Circuit Voltage ◽  
Uv Light ◽  
Open Circuit ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Voltage Loss

scholarly journals Regulation of the photosynthetic apparatus under fluctuating growth light

2012 ◽  
Vol 367 (1608) ◽  
pp. 3486-3493 ◽  
Author(s):  
Mikko Tikkanen ◽  
Michele Grieco ◽  
Markus Nurmi ◽  
Marjaana Rantala ◽  
Marjaana Suorsa ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photosynthetic Activity ◽  
Photosynthetic Apparatus ◽  
Metabolic Energy ◽  
Thermal Dissipation ◽  
Transfer Reactions ◽  
Photosynthetic Machinery ◽  
New Hypothesis ◽  
White Light Intensity

Safe and efficient conversion of solar energy to metabolic energy by plants is based on tightly inter-regulated transfer of excitation energy, electrons and protons in the photosynthetic machinery according to the availability of light energy, as well as the needs and restrictions of metabolism itself. Plants have mechanisms to enhance the capture of energy when light is limited for growth and development. Also, when energy is in excess, the photosynthetic machinery slows down the electron transfer reactions in order to prevent the production of reactive oxygen species and the consequent damage of the photosynthetic machinery. In this opinion paper, we present a partially hypothetical scheme describing how the photosynthetic machinery controls the flow of energy and electrons in order to enable the maintenance of photosynthetic activity in nature under continual fluctuations in white light intensity. We discuss the roles of light-harvesting II protein phosphorylation, thermal dissipation of excess energy and the control of electron transfer by cytochrome b 6 f , and the role of dynamically regulated turnover of photosystem II in the maintenance of the photosynthetic machinery. We present a new hypothesis suggesting that most of the regulation in the thylakoid membrane occurs in order to prevent oxidative damage of photosystem I.

A Diterpene γ-Lactone Derivative from Pterodon polygalaeflorus Benth. as a Photosystem II Inhibitor and Uncoupler of Photosynthesis

2006 ◽  
Vol 61 (3-4) ◽  
pp. 227-233 ◽  
Author(s):  
Beatriz King-Díaz ◽  
Flávio J. L. dos Santos ◽  
Mayura M. M. Rubinger ◽  
Dorila Piló -Veloso ◽  
Blas Lotina-Hennsen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Transport Rate ◽  
Atp Synthesis ◽  
Transport Rate ◽  
Hill Reaction ◽  
Oxygen Evolving Complex ◽  
Photosynthesis Inhibition ◽  
Chlorophyll A Fluorescence Transient ◽  
Oxygen Evolving

6α,7β-Dihydroxyvouacapan-17β-oic acid (1) was isolated from Pterodon polygalaeflorus Benth. Modification of 1 yielded 6α-hydroxyvouacapan-7β,17β-lactone (2) and then 6-oxovouacapan- 7β,17β-lactone (3). Photosynthesis inhibition by 3 was evaluated in spinach chloroplasts. The uncoupled non-cyclic electron transport rate and ATP synthesis were inhibited by 3, which behaved as a Hill reaction inhibitor. Furthermore, 3 acted as an uncoupler because it enhanced the basal and phosphorylating electron transport rate on thylakoids. This last property of 3 was corroborated when it was observed that it enhances the Mg2+-ATPase activity. In contrast, 3 did not affect photosystem I (PSI) activity. Analysis of the partial photosystem II (PSII) reactions from water to DCPIPox and water to silicomolybdate allowed to locate the inhibition sites at the redox components of PSII. The OJIP test of the chlorophyll a fluorescence transient confirmed that the inhibition sites were 1.) the oxygen-evolving complex (OEC) and 2.) by the formation of silent centers in the non-QA reducing centers.

Current status of the role of Cl− ion in the oxygen-evolving complex

2007 ◽  
Vol 93 (1-3) ◽  
pp. 111-121 ◽  
Author(s):  
Hana Popelková ◽  
Charles F. Yocum
Keyword(s):  
Current Status ◽  
Oxygen Evolving Complex ◽  
Oxygen Evolving

Antagonistic Effects of α-Tocopherol and α-Tocoquinone in the Regulation of Cyclic Electron Transport around Photosystem II

1997 ◽  
Vol 52 (11-12) ◽  
pp. 766-774 ◽  
Author(s):  
J. Kruk ◽  
K. Burda ◽  
A. Radunz ◽  
K. Strzałka ◽  
G. H. Schmid
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Transition Probability ◽  
Continuous Illumination ◽  
Oxygen Evolving Complex ◽  
Cyclic Electron Transport ◽  
State Distribution ◽  
Ps Ii ◽  
Oxygen Evolving

Abstract α-Tocoquinone (α-TQ ) and α-tocopherol (α-TOC) which cannot substitute for plastoquinone-9 (PQ-A) as an electron acceptor from photosystem II (PS II), influence the oxygen evolution activity of thylakoid membranes under continuous illumination. In the presence of the herbicide DCMU and the protonophore FCCP which stimulate cyclic electron transport around PS II, α-TQ decreased oxygen evolution whereas α-TOC enhanced it. The effects are attributed to a stimulation or an inhibition of cyclic electron transport around PS II by α-TQ and α-TOC, respectively. Results of flash light experiments on PS II preparations show that both α-TQ and α-TOC increased the d-parameter which describes the transition probability from the S3- to the S0-state of the oxygen-evolving complex, although to a smaller extent when PQ-A is added alone to the preparations. The initial S-state distribution in darkadapted samples was changed only upon PQ-A addition and influenced neither by α-TQ nor by α-TO C supplementation. These effects indicate different kinds of interaction of PQ-A, α-TQ and α-TOC with the PS II components. α-TQ increased and α-TOC decreased the “total miss” parameter both in the presence or absence of PQ-A. A possible site of interaction of α-TQ and α-TO C with the cyclic electron transport around PS II is suggested.

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