O2-Dependent Electron Flow in Intact Spinach Chloroplasts: Properties and Possible Regulation of the Mehlerascorbate Peroxidase Cycle

Schreiber, Ulrich; Hormann, Henning; Asada, Kozi; Neubauer, Christian

doi:10.1007/978-94-009-0173-5_419

Cited by 31 publications

(31 citation statements)

References 30 publications

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“…Hormann et al (1994) and Schreiber et al (1995a) demonstrated a linear relationship between ap and (Dp, at high irradiances but a deviation from nonlinearity at high quantum efficiencies, i.e. at low irradiances.…”

Section: Discussionmentioning

confidence: 92%

“…high quantum yields) and are ascribed to the presence of PSI1 heterogeneity (e.g. Schreiber et al 1995a;Hormann et al 1994). However, microalgae have a more flexible photosynthetic machinery and can more easily adjust their optical properties.…”

Section: Discussionmentioning

confidence: 99%

“…The algae were dark-adapted for 15 min and subsequently exposed for 2-4 min to increasing irradiances of white light. Steady-state fluorescence (F,) and maximal fluorescence (F,,,') were measured using a PAM-Walz 101-103 fluorometer (H. Walz, Effeltrich; Schreiber et al 1986). A light-emitting diode delivered a low-intensity modulated measuring light beam that was weak enough not to induce any significant variable fluorescence.…”

Section: Methodsmentioning

confidence: 99%

“…Because measurements of @oz and @'co, are laborious and time-consuming, much attention has been focused lately on the use of variable chlorophyll fluorescence as a tool to measure the quantum yield of charge separation in photosystem II (PSIl) reaction centers (Genty et al 1989). This technique is rapid and noninvasive and may offer high temporal and spatial resolution when used in field measurements (Schreiber et al 1986). Theoretically, the rate of noncyclic photosynthetic electron transport of a PSI1 (J) can be calculated from the quantum yield of PSI1 charge separation (a,,) according to J = @,J%s,,r…”

Section: Introductionmentioning

confidence: 99%

“…Nonlinearity of @,, and &(,, was observed in marine microalgae (Schreiber et al 1995a), macroalgae (Hanelt and Nultsch 1995), and higher plants (Biehler and Fock 1995). In contrast, a linear relationship between @,, and @'oz was observed in green alga (Kroon 1991;Holmes et al 1989) and in some higher plants (Strand and Lundmark 1995;Genty et al 1992).…”

mentioning

confidence: 99%

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Light dependence of quantum yields for PSII charge separation and oxygen evolution in eucaryotic algae

Flameling

Kromkamp

1998

Limnology & Oceanography

126

105

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Quantum yields of photosystcm I1 (PSII) charge separation (@& and oxygen production ((I) (,,) were determined by simultaneous measurements of oxygen production and variable fluorescence in four different aquatic microalgae representing three different taxonomic groups: the freshwater alga Scenedesmus protuberans (Chlorophyceae) and the marine algae Phneorystis globosa (Prymnesiophyceae), Emiliania huxleyi (Prymnesiophyceae), and Phaeodactylum tricornutum (Bacillariophyceae). In S. protuberans, P. tricornutum, and E. huxleyi, light-dependent variability was observed in the ratio of a(,,, to a,,, i.c. in the number of oxygen molecules produced per electron generated by PSII. The ratio ao,:@,, was highly variable at low light intensities (E < OSE,), and at higher light intensities (E > OSE,) @(,, : @,, showed a nonlinear decrease with increasing light intensity. In contrast, in P. globosa. a trend in a<,, : @,, could not be distinguished, and this species showed a decrease in @'o, : $ during the day, indicating a dependency of a(,, : a,, on light history. Additionally, considerable interspecific quantitative differences in a(,, : a,, were observed. Two possible interpretations to explain the variability in '.I+)! : a, are discussed. Assuming that 0, is a reliable measure of the quantum yield for charge separation at PSII, one interpretation is that net oxygen production is influenced by processes that consume oxygen or affect linear electron transport (e.g. cyclic electron transport around PSII, pseudocyclic electron transport in the Mehler reaction, Rubisco oxygenase activity, and lightdependent mitochondrial respiration). A second interpretation, however, suggests that at saturating light, changes in photosynthesis turnover time occur, such that $ does not predict the steady-state O2 yield.Quantum yields of phytoplankton photosynthesis are usually defined as the quantum yields for O? production (CacjL) or C fixation (@c,,,) (Kok 1948;Myers 1980;Babin et al. 1996). Because measurements of @oz and @'co, are laborious and time-consuming, much attention has been focused lately on the use of variable chlorophyll fluorescence as a tool to measure the quantum yield of charge separation in photosystem II (PSIl) reaction centers (Genty et al. 1989). This technique is rapid and noninvasive and may offer high temporal and spatial resolution when used in field measurements (Schreiber et al. 1986). Theoretically, the rate of noncyclic photosynthetic electron transport of a PSI1 (J) can be calculated from the quantum yield of PSI1 charge separation (a,,) according to J = @,J%s,,rwhere E is the incident light intensity and cr,,,, is the absorption cross section of PSII, which determines the fraction of the incident light intensity that is actually used by PSI1 (e.g. Kolber and Falkowski 1993; Kroon 1991; Hofstraat et al. 1994, Biehler andFock 1995). In order to use J as a measure for photosynthesis, the relationships between @,,, @coL, and @coz have to be well established. According to the stoichiometry of the Z-schem...

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Light dependence of quantum yields for PSII charge separation and oxygen evolution in eucaryotic algae

Flameling

Kromkamp

1998

Limnology & Oceanography

126

105

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Characterisation of a H2O2-oxidisable cytochrome b-559 in intact chloroplasts with a new type of LED Array Spectrophotometer

Heimann

Schreiber

1996

Photosynth Res

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Cytochrome (cyt) b-559 absorbance changes in intact chloroplasts were deconvoluted using a previously described LED-Array-Spectrophotometer (Klughammer et al. (1990), Photosynth Res 25: 317-327). When intact chloroplasts were isolated in the presence of ascorbate, approx. 15% of the total cyt b-559 could be transiently oxidised by 200 μM H2O2 in the dark. This fraction displays low-potential properties, as it can be also oxidised by menadione in the presence of 5 mM ascorbate. Heat pretreatment increased the size of this fraction by a factor of 3-4. Low concentrations of cyanide (in the μM range) prolonged the oxidation time while high concentrations suppressed the oxidation (I50=1.5 mM KCN). The former KCN-effect relates to inhibition of ascorbate dependent H2O2-reduction which is catalysed by ascorbate peroxidase, whereas the latter effect reflects competition between H2O2 and CN(-) for the same binding site at the cytochrome heme. In the light, much lower concentrations of H2O2 were required to obtain oxidation, the amplitude depending on light intensity and on the concentration of the added H2O2, but never exceeding approx. 15% of the total cyt b-559. In the light, but not in the dark, H2O2 also induced the transient oxidation of a cyt f fraction similar in size to the H2O2-oxidisable cyt b-559 fraction. In this case, H2O2 serves as an acceptor of Photosystem I in conjunction with the ascorbate peroxidase detoxification system. Light can also induce oxidation of a 15% cyt b-559 fraction without H2O2-addition, if nitrite is present as electron acceptor and the chloroplasts are depleted of ascorbate. It is concluded that light-induced cyt b-559 oxidation in vivo is likely to be restricted to the H2O2-oxidisable cyt b-559 LP fraction and is normally counteracted by ascorbate.

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Oxygen and electron flow in C 4 photosynthesis: Mehler reaction, photorespiration and CO 2 concentration in the bundle sheath

Laisk

Edwards

1998

Planta

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O2-Dependent Electron Flow in Intact Spinach Chloroplasts: Properties and Possible Regulation of the Mehlerascorbate Peroxidase Cycle

Cited by 31 publications

References 30 publications

Light dependence of quantum yields for PSII charge separation and oxygen evolution in eucaryotic algae

Light dependence of quantum yields for PSII charge separation and oxygen evolution in eucaryotic algae

Characterisation of a H2O2-oxidisable cytochrome b-559 in intact chloroplasts with a new type of LED Array Spectrophotometer

Oxygen and electron flow in C 4 photosynthesis: Mehler reaction, photorespiration and CO 2 concentration in the bundle sheath

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