Primary electron acceptors in plant photosynthesis

Fajer, J.; Davis, M. S.; Forman, A.; Klimov, Vyacheslav V.; Dolan, E.; Kê, Bacon

doi:10.1021/ja00543a062

Cited by 64 publications

(25 citation statements)

References 2 publications

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“…This suggestion is supported by observations reported on the electron acceptor A1 in photosystern I of higher plants, which is thought to be a monomeric or dimeric Chl a, and which might correspond to X~ in P. aestuarii. In photosystem I particles in which the iron-sulfur center A2 was reduced,g-values of 2.0033 [19] and 2.004 [12] have been reported for A i-. However, in photosystem I preparations which did not contain A2, the g-value of A[ [20] resembled that of Chl a-in vitro [21 ].…”

Section: Resultsmentioning

confidence: 99%

Evidence for photoreduction of monomeric bacteriochlorophyll a as an electron acceptor in the reaction center of the green photosynthetic bacterium Prosthecochloris aestuarii

et al. 1981

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Section: Resultsmentioning

confidence: 99%

Evidence for photoreduction of monomeric bacteriochlorophyll a as an electron acceptor in the reaction center of the green photosynthetic bacterium Prosthecochloris aestuarii

et al. 1981

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“…These data suggest that A4t can be used to estimate the relative growth rates of nitrogen-deficient algae. It has been shown that variable fluorescence is a result of a charge recombination between P680+ and Phaeo-when QA is reduced (8,19) P680' Phaeo-QA-P680* Phaeo QA-, followed by radiative deactivation of P680* within the pigment bed (15,16,18). Thus, changes in At., reflect a change in the fraction of PSII traps which can perform photochemistry, and imply changes in photosynthetic energy conversion efficiency in PSII (2).…”

Section: Methodsmentioning

confidence: 99%

Effects of Growth Irradiance and Nitrogen Limitation on Photosynthetic Energy Conversion in Photosystem II

Kolber

Zehr²,

Falkowski³

1988

Plant Physiol.

450

356

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ABSTRACrPhotosynthetic energy conversion was investigated in five species of marine unicellular algae, (Dunaliella tertiolecta, Thalassiosira pseudonana, T. weisflogii, Skeletorema costatum, Isochrysis galbana) representing three phylogenetic classes, which were grown under steady state conditions with either light or inorganic nitrogen as a limiting factor. Using a pump and probe fluorescence technique we measured the maximum change in variable fluorescence yields, the flash intensity saturation curves for the change in fluorescence yields and the kinetics of the decay in fluorescence yields. Under all growth irradiance levels nutrient replete cells exhibited approximately the same changes in fluorescence yields and similar fluorescence decay kinetics. The apparent relative absorption cross-section of photosystem II, calculated from the slope of the flash intensity saturation curves, generally increased as cells shade adapted. The decay kinetics of the fluorescence yield following a saturating pump flash can be expressed as the sum of three exponential components, with half-times of 160 and 600 microseconds and 30 to 300 milliseconds. The relative contribution of each component did not change significantly with growth irradiance. As cells became more nitrogen limited, however, the maximum change in fluorescence yield decreased, and was accompanied by a decrease in the proportion of a 160 microsecond fluorescence decay component, which corresponds to the transfer of electrons from QA-to QB. Changes in fluorescence yields were also accompanied by changes in the levels of Dl, a protein which is integral in reaction center II, and CP47, a chlorophyll protein forming part of the core of photosystem II. These results are consistent with a loss of functional photosystem II reaction centers. Moreover, in spite of losses of total cellular chlorophyll, which invariably accompanied nitrogen limitation, the apparent absorption cross-sections of photosystem II increased. Our results suggest that nitrogen limitation leads to substantial decreases in photosynthetic energy conversion efficiency.In PSII, four basic processes must be coordinated to maximize photochemical energy conversion, namely, light harvesting, trapping of excitation energy and primary charge separation, stabilization of charge separation on secondary acceptors, and the repopulation of the primary electron donor leading to the oxidation of water. Each of these processes requires the synthesis and integration of a number of specific proteins, together with their prosthetic groups. In eucaryotic algae, which are exposed to large variations in their environment, the photosynthetic apparatus is remarkably plastic. dance of proteins forming reaction centers, intersystem electron carriers, and light harvesting Chl complexes is strongly related to growth irradiance (9,10,12,21,25,30). Protein synthesis is also dependent on the availability ofinorganic nitrogen. A suboptimal supply of inorganic nitrogen leads to chlorosis (3,20,27), which reflects a change in the re...

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“…We proposed that this signal arose from a reduced monomeric chlorophyll electron carrier and obtained kinetic evidence for a flash induced EPR transient decaying in the p time range corresponding to this component [7]. Support for the identification of the component as a monomeric chlorophyll came from ENDOR experiments [8]. A spin-polarised triplet EPR signal has also been detected in photosystem I [9]; using LDS-treated particles which lacked the iron-sulphur centres, it was shown that reduction of the chlorophyll intermediary carrier decreased the amplitude of the triplet signal [lo].…”

Section: Introductionmentioning

confidence: 99%

Identification of multiple components in the intermediary electron carrier complex of photosystem I

1982

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Illumination at 230 K of dithionite‐reduced particles results in the appearance of an EPR detectable radical 13 G wide with g = 2.0033. This radical is formed in a ratio of 2.28 (±0.5)/P700. Investigation of the time course of formation shows two components are present. One (A 1) has g = 2.0051 and the other (A o g= 2.0024. Reduction of A 1 results in an increase in reaction centre triplet formation, subsequent reduction of A o results in a decrease of triplet formation to the base level. We propose that these components function sequentially in the transfer of electrons from P700 to the iron—sulphur acceptors.

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Primary electron acceptors in plant photosynthesis

Cited by 64 publications

References 2 publications

Evidence for photoreduction of monomeric bacteriochlorophyll a as an electron acceptor in the reaction center of the green photosynthetic bacterium Prosthecochloris aestuarii

Evidence for photoreduction of monomeric bacteriochlorophyll a as an electron acceptor in the reaction center of the green photosynthetic bacterium Prosthecochloris aestuarii

Effects of Growth Irradiance and Nitrogen Limitation on Photosynthetic Energy Conversion in Photosystem II

Identification of multiple components in the intermediary electron carrier complex of photosystem I

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