Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence
The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent qu...
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| Autor*in: |
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| Format: |
E-Artikel |
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| Sprache: |
Englisch |
| Erschienen: |
1987 |
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| Reproduktion: |
Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 |
|---|---|
| Übergeordnetes Werk: |
in: Biochimica et Biophysica Acta (BBA)/Bioenergetics - Amsterdam : Elsevier, 894(1987), 2, Seite 198-208 |
| Übergeordnetes Werk: |
volume:894 ; year:1987 ; number:2 ; pages:198-208 |
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| 520 | |a The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. | ||
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(DE-627)NLEJ18569618X (DE-599)GBVNLZ18569618X DE-627 ger DE-627 rakwb eng Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence 1987 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 Weis, E. oth Berry, J.A. oth in Biochimica et Biophysica Acta (BBA)/Bioenergetics Amsterdam : Elsevier 894(1987), 2, Seite 198-208 (DE-627)NLEJ177198850 (DE-600)2209370-9 0005-2728 nnns volume:894 year:1987 number:2 pages:198-208 http://linkinghub.elsevier.com/retrieve/pii/0005-2728(87)90190-3 GBV_USEFLAG_H ZDB-1-SDJ GBV_NL_ARTICLE AR 894 1987 2 198-208 |
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(DE-627)NLEJ18569618X (DE-599)GBVNLZ18569618X DE-627 ger DE-627 rakwb eng Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence 1987 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 Weis, E. oth Berry, J.A. oth in Biochimica et Biophysica Acta (BBA)/Bioenergetics Amsterdam : Elsevier 894(1987), 2, Seite 198-208 (DE-627)NLEJ177198850 (DE-600)2209370-9 0005-2728 nnns volume:894 year:1987 number:2 pages:198-208 http://linkinghub.elsevier.com/retrieve/pii/0005-2728(87)90190-3 GBV_USEFLAG_H ZDB-1-SDJ GBV_NL_ARTICLE AR 894 1987 2 198-208 |
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(DE-627)NLEJ18569618X (DE-599)GBVNLZ18569618X DE-627 ger DE-627 rakwb eng Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence 1987 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 Weis, E. oth Berry, J.A. oth in Biochimica et Biophysica Acta (BBA)/Bioenergetics Amsterdam : Elsevier 894(1987), 2, Seite 198-208 (DE-627)NLEJ177198850 (DE-600)2209370-9 0005-2728 nnns volume:894 year:1987 number:2 pages:198-208 http://linkinghub.elsevier.com/retrieve/pii/0005-2728(87)90190-3 GBV_USEFLAG_H ZDB-1-SDJ GBV_NL_ARTICLE AR 894 1987 2 198-208 |
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(DE-627)NLEJ18569618X (DE-599)GBVNLZ18569618X DE-627 ger DE-627 rakwb eng Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence 1987 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 Weis, E. oth Berry, J.A. oth in Biochimica et Biophysica Acta (BBA)/Bioenergetics Amsterdam : Elsevier 894(1987), 2, Seite 198-208 (DE-627)NLEJ177198850 (DE-600)2209370-9 0005-2728 nnns volume:894 year:1987 number:2 pages:198-208 http://linkinghub.elsevier.com/retrieve/pii/0005-2728(87)90190-3 GBV_USEFLAG_H ZDB-1-SDJ GBV_NL_ARTICLE AR 894 1987 2 198-208 |
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(DE-627)NLEJ18569618X (DE-599)GBVNLZ18569618X DE-627 ger DE-627 rakwb eng Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence 1987 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. Elsevier Journal Backfiles on ScienceDirect 1907 - 2002 Weis, E. oth Berry, J.A. oth in Biochimica et Biophysica Acta (BBA)/Bioenergetics Amsterdam : Elsevier 894(1987), 2, Seite 198-208 (DE-627)NLEJ177198850 (DE-600)2209370-9 0005-2728 nnns volume:894 year:1987 number:2 pages:198-208 http://linkinghub.elsevier.com/retrieve/pii/0005-2728(87)90190-3 GBV_USEFLAG_H ZDB-1-SDJ GBV_NL_ARTICLE AR 894 1987 2 198-208 |
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quantum efficiency of photosystem ii in relation to 'energy'-dependent quenching of chlorophyll fluorescence |
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Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence |
| abstract |
The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. |
| abstractGer |
The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. |
| abstract_unstemmed |
The balance between light-dependent reactions and electron-consuming reactions in intact sunflower leaves was varied by changing the incident light-flux at constant intercellular CO"2 concentration. Measurements of fluorescence quenching were compared to measurements of the rate and apparent quantum yield of whole-chain electron transport at a number of steady-state conditions. The steady-state quantum yield declined with increasing light intensity, falling at the highest intensity to approx. 40% of the maximum value observed in low light. The coefficient for photochemical quenching, q"Q, was near 1 in low light and only declined to 0.7 at the highest light, indicating that there was very little feedback from accumulation of reduced electron carriers. On the other hand, there was a large increase in q"E, the coefficient for 'energy'-dependent quenching, as the quantum yield fell. We found that these changes in the steady-state quantum yield, Φ"s, could be related to the changes in fluorescence quenching by an empirical equation, Φ"s = q"Q(0.32 - 0.17 q"E) which accounted for variation in Φ"s resulting from light saturation or changes in CO"2 concentration. We develop a hypothesis that Photosystem (PS) II centers may be converted to an altered state (possibly mediated by the chloroplast ΔpH) which has very little variable fluorescence and a lowered photochemical yield. We develop a kinetic explanation for the properties of the altered form of PS II, and we propose that this mechanism (indicated by q"E) functions together with the accumulation of reduced Q"A (indicated by q"Q) to regulate the rate of net photochemistry by PS II when - with increasing light or decreasing CO"2 - the potential rate of net photochemistry exceeds that for carbon metabolism. The latter mechanism apparently permits down-regulation of PS II to occur without strong accumulation of reduced Q"A, except during transients or under the most extreme conditions. |
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Quantum efficiency of Photosystem II in relation to 'energy'-dependent quenching of chlorophyll fluorescence |
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