Simultaneous Saturation of Variable Fluorescence Yield and Photoacoustically Monitored Thermal Emission in Thylakoid Membranes

Carpentier, Robert; Owens, Thomas G.; Leblanc, Roger M.

doi:10.1111/j.1751-1097.1991.tb03672.x

Cited by 9 publications

(11 citation statements)

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“…In most studies, the inactive sample with closed reaction centers was obtained by superimposition of a nonmodulated background light of saturating intensity on the low-intensity modulated measuring beam (3-6). The energy-storage yield has been correlated with the electron transport status (7,8), and it was suggested that electron transfer from water to the plastoquinone (PQ) pool was responsible for the stored energy (8)(9)(10).…”

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Variable thermal emission and chlorophyll fluorescence in photosystem II particles.

Allakhverdiev

Klimov

Carpentier

1994

Proc. Natl. Acad. Sci. U.S.A.

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In photosynthetic systems, the absorbed light energy is used to generate electron transport or it is lost in the form of fluorescence and thermal emission. While fluorescence can be readily measured, the detection of thermal deactivation processes can be achieved by the photoacoustic technique. In that case, the pressure wave generated by the thermal deactivations in a sample irradiated with modulated light is detected by a sensitive microphone. The relationships between the yield of fluorescence and thermal emissions measured simultaneously were analyzed by using a spinach photosystem II (PSH)-enriched preparation. It is shown that the quenching of fluo- In the photosynthetic apparatus, the absorbed light energy is either used to generate electron transport that is initiated by charge separation at the level of photosystems I and II (PSI and PSII), or the energy is lost through fluorescence and thermal emission. Fluorescence can be readily measured, but photoacoustic (PA) spectroscopy has been advantageously used to study the thermal deactivation processes in photosynthetic materials (1). In that case, a solid or semisolid sample is irradiated with modulated light in a closed cell. The thermal deactivations generate a periodic heat flow in the The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. surrounding gas medium that produces a pressure wave transduced into an electric signal by a sensitive microphone. Most usefully, the difference between the thermal emission yields ofactive and inactive samples allows the determination of the photochemical energy-storage yield (2). In most studies, the inactive sample with closed reaction centers was obtained by superimposition of a nonmodulated background light of saturating intensity on the low-intensity modulated measuring beam (3-6). The energy-storage yield has been correlated with the electron transport status (7,8), and it was suggested that electron transfer from water to the plastoquinone (PQ) pool was responsible for the stored energy (8-10).Similarly, part of the fluorescence emission (the so-called variable fluorescence) is closely related to the redox state of the secondary acceptors QA and QB in PSII and therefore is greatly influenced by the electron transport status (11). Thus, a strong interdependence between the yield of energy storage and the yield of variable fluorescence can be suggested (10). The correlation between chlorophyll (Chl) fluorescence and the PA signal has been studied in intact leaves (12, 13). However, the interpretations were complicated by the participation of PSI in the thermal signal and by a photobaric contribution due to oxygen evolution.A PSII submembrane fraction depleted of PSI should constitute the simplest model to study the relationship between variable fluorescence emission and thermal energy storage. The thermal emission behavior of such preparations has been...

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“…Thus, a strong interdependence between the yield of energy storage and the yield of variable fluorescence can be suggested (10). The correlation between chlorophyll (Chl) fluorescence and the PA signal has been studied in intact leaves (12,13).…”

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confidence: 99%

Variable thermal emission and chlorophyll fluorescence in photosystem II particles.

Allakhverdiev

Klimov

Carpentier

1994

Proc. Natl. Acad. Sci. U.S.A.

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“…The same effect was seen with a measuring light of lower intensity (70 ttmol m -2 s-l), though the values for the apparent ES were higher in this case, as expected for an approach to more light limiting conditions (cf. Carpentier et al 1991 and references cited therein). That this effect was not related to photosynthesis, but rater to the average temperature change was further demonstrated with a leaf sample that was kept in boiling water for 15 s. In this case there was again the steady rise in the apparent ES at high background light intensities, but below 2000/zmol m -2 s -1 the apparent ES was zero (Fig.…”

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The use of photothermal radiometry in assessing leaf photosynthesis: II. Correlation of energy storage to Photosystem II fluorescence parameters

1994

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Following the first part of this work (Malkin et al. (1991) Photosynth Res 29: 87-96), where modulated photothermal radiometry (PTR) was used to measure energy storage (ES) in intact leaves as a function of P700 redox state, we report here on simultaneous ES and fluorescence measurements, which characterize the state of PS II. PTR monitors the conversion of modulated light into heat by measuring the modulated infra-red radiation emitted from the sample. The ratio [PTR+-PTR-]/PTR+, where PTR indicates the PTR signal and the subscripts +,- indicate the presence or absence of saturating background light, is used to quantitate ES. We searched carefully for the right conditions where the background light does not introduce a significant rise in the leaf temperature, which influences the PTR signal as such, otherwise the above ratio deviates from the true ES. Under such conditions, ES and the fluorescence parameters, F (momentary fluorescence level) Fm' (fluorescence of fully reduced PS II reaction centers) were measured during the induction phase of photosynthesis and in the steady state. ES and the parameter γ=(Fm'-F)/Fm', considered by Genty et al. ((1989) Biochim Biophys Acta 990: 87-92) to reflect the yield of PS II, had similar kinetics during the induction phase. Both reached a final maximum plateau after about 4-5 min. of illumination. In different experiments, where the measuring light intensities varied, γ was approximately linearly related to ES. This linear relationship was found in the same way also in steady-state measurements, where these parameters varied by using different background light intensities. Extrapolation to an ES value of zero indicates a finite non-zero value of γ. A possible explanation for this may be found in the existence an electron transport cycle around PS II which does not store energy in the range corresponding to the modulation frequency used (ca. 3.6 Hz).

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“…The energy storage yield was correlated with the electron transport rate (Carpentier et al 1989) and it was suggested that energy storage in PS II is related to the reduction of the plastoquinone pool (Carpentier et al 1989. The portion of thermal emission that varies with the redox state of the photosystems (variable thermal emission) was further correlated with the intensity of variable fluorescence (Carpentier et al 1991).…”

Section: Introductionmentioning

confidence: 96%

Variable thermal dissipation in a Photosystem I submembrane fraction

Velitehkova

Carpentier

1994

Photosynth Res

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Photoacoustic spectroscopy was used to study the thermal deactivation processes in a Photosystem I submembrane fraction isolated from spinach. A large part of the thermal dissipation was variable. The yield of this variable thermal emission depended on the redox state of the Photosystem. It increased with the measuring modulated light intensity coinciding with the gradual closure of the reaction centers. Thermal deactivation was maximal when the reaction centers were closed by a saturating illumination. Extrapolation of the data at zero light intensity indicated that the yield of non-variable thermal emission represented about 37% of the maximal emission. The presence of methylviologen as artificial electron acceptor decreased the yield of variable thermal emission whereas inhibition following heat stress treatments increased it. The significance of the variable and non-variable components of thermal dissipation is discussed and the measured energy storage is suggested to originate from the reduction of the plastoquinone pool during cyclic electron transport around Photosystem I.

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Simultaneous Saturation of Variable Fluorescence Yield and Photoacoustically Monitored Thermal Emission in Thylakoid Membranes

Cited by 9 publications

References 28 publications

Variable thermal emission and chlorophyll fluorescence in photosystem II particles.

Variable thermal emission and chlorophyll fluorescence in photosystem II particles.

The use of photothermal radiometry in assessing leaf photosynthesis: II. Correlation of energy storage to Photosystem II fluorescence parameters

Variable thermal dissipation in a Photosystem I submembrane fraction

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