Photosystem II Heterogeneity in Chloroplasts

Melis, Anastasios; Guenther, G. E.; Morrissey, Peter J.; Ghirardi, Maria L.

doi:10.1007/978-94-009-2823-7_4

Cited by 14 publications

(11 citation statements)

References 37 publications

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“…So, it was found important to complete the analysis of the PS II function by additional, independent measurements, namely the kinetics of chlorophyll fluorescence changes during a dark-light transition (Kautsky effect), the fluorescence decay after a single turnover flash and the effect of an electron donor to PS II (hydroxylamine). Table 1 shows the main features of the Kautsky-type induction curves of chlorophyll fluorescence (O-I-P phase) measured in darkadapted potato leaves suddenly illuminated with moderate white light, whereas the rapid O-I fluorescence rise has been attributed to QA reduction in the Qa-non-reducing PS II reaction centers (Melis et al 1988), the second phase (I-P) reflects accumulation of QA in 'active' centers with efficient electron transfer to plastoquinone, with the lag (t) in the transition from I to P corresponding to the time needed for electrons to accumulate in the plastoquinone pool (Malkin 1971). Photoinhibitory light stress reduced P and increased t, indicating lower efficiency of PS II to produce electrons (as more time is necessary to reduce the plastoquinone pool).…”

Section: Resultsmentioning

confidence: 99%

Photoinhibition of photosynthesis in chilled potato leaves is not correlated with a loss of Photosystem-II activity

1994

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When 23 °C-grown potato leaves (Solanum tuberosum L.) were irradiated at 23 °C with a strong white light, photosynthetic electron transport and Photosystem-II (PS II) activity were inhibited in parallel. When the light treatment was given at a low temperature of 3 °C, the photoinhibition of photosynthesis was considerably enhanced, as expected. Surprisingly, no such stimulation of photoinhibition was observed with respect to the PS II function. A detailed functional analysis of the photosynthetic apparatus, using in-vivo fluorescence, absorbance, oxygen and photoacoustic measurements, and artificial electron donors/acceptors, showed a pronounced alteration of PS I activity during light stress at low temperature. More precisely, it was observed that both the pool of photooxidizeable reaction center pigment (P700) of PS I and the efficiency of PS I to oxidize P700 were dramatically reduced. Loss of P700 activity was shown to be essentially dependent on atmospheric O2 and to require a continued flow of electrons from PS II, suggesting the involvement of the superoxide anion radical which is produced by the interaction of O2 and the photosynthetic electron-transfer chain through the Mehler reaction. Mass spectrometric measurements of O2 exchange by potato leaves under strong illumination did not reveal, however, any stimulation of the Mehler reaction at low temperature, thus leading to the conclusion that O2 toxicity mainly resulted from a chilling-induced inhibition of the scavenging system for O2-radicals. Support for this interpretation was provided by the light response of potato leaves infiltrated with an inhibitor (diethyldithiocarbamate) of the chloroplastic Cu-Zn superoxide dismutase. It was indeed possible to simulate the differential inhibition of the PS II photochemical activity and the linear electron transport observed during light stress at low temperature by illuminating at 23 °C diethyldithiocarbamate-poisoned leaves. The experimental data presented here suggests that (i) the previously reported resistance of PS I to photoinhibition damage in-vivo is not an intrinsic property of PS I but results from efficient protective systems against O2 toxicity, (ii) PS I is photoinhibited in chilled potato leaf due to the inactivation of this PS I defence system and (iii) PS I is more sensitive to superoxide anion radicals than PS II.

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Section: Resultsmentioning

confidence: 99%

Photoinhibition of photosynthesis in chilled potato leaves is not correlated with a loss of Photosystem-II activity

1994

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“…This is not the case with the increase in the relative concentration of PSII, centers, which were detected in the absence of light. These centers, which have a smaller antenna size and are located in the nonappressed thylakoid regions (Melis et al, 1988), have been suggested to be a reserve pool of PSII to replace photoinhibited PSII centers (Melis, 1985;Tyystjarvi and Aro, 1990). However, the p centers created by heat treatment are unlikely to have such a role; rather, they are formed by the disconnection of LHCII from PSII (Sundby et al, 1986).…”

Section: Discussionmentioning

confidence: 99%

Effect of High Temperature on Photosynthesis in Beans (I. Oxygen Evolution and Chlorophyll Fluorescence)

1996

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We studied the effect of increasing temperature on photosynthesis i n two bean (Phaseolus vulgaris L.) varieties known to differ in their resistance to extreme high temperatures, Blue Lake (BL), commercially available i n the United Kingdom, and Barbucho (BA), noncommercially bred in Chile. We paid particular attention to the energy-transducing mechanisms and structural responses inferred from fluorescence kinetics. The study was conducted in nonphotorespiratory conditions. lncreases in temperature resulted in changes i n the fluorescence parameters nonphotochemical quenching (qN) and photochemical quenching (qP) in both varieties, but to a different extent. I n BL and BA the increase i n qP and the decrease in qN were either completed at 30°C or slightly changed following increases from 30 to 35°C. No indication of photoinhibition was detected at any temperature, and the ratio of the quantum efficiencies of photosystem I1 (PSII) and O , evolution remained constant from 20 to 35°C. Measurements of 77-K fluorescence showed an increase in the photosystem I (PSI)/PSII ratio with temperature, suggesting an increase in the state transitions. I n addition, measurements of fast-induction fluorescence revealed that the proportion of PSII, centers increased with increasing temperatures. The extent of both changes were maximum at 30 to 35"C, coinciding with the ratio of rates at temperatures differing by 10°C for oxygen evolution.High temperature affects the photosynthetic functions of plants by its effect on the rate of chemical reactions and on structural organization. It has been previously reported that high temperatures are responsible for changes in the thylakoid membrane, altering not only its physicochemical properties, but also its functional organization (Berry and Bjorkman, 1980). PSII, particularly, is the most sensitive component of the photosynthetic system (Berry and Bjorkman, 1980;Mamedov et al., 1993). Extreme high temperatures affect the functioning of the O,-evolving system (Yamashita and Butler, 1968), resulting in the release of functional manganese ions from the complex (Nash et al., 1985). This release may be the result of reductions by peroxides or superoxides (Thomson et al., 1989). PSII also * Supported by a scholarship received by C.P. from the Ministry responds to the range of temperatures below those causing inhibition or destruction of the complex, with consequences for thylakoid organization and functioning. Separation of the LHCII from the core center induces destacking of the grana (Gounaris et al., 1984) and temperatureinduced migration of the reaction center (PSII,) or LHCII (state transition) to the nonappressed region, which would have consequences for the energy redistribution between PSI and PSII.Most of the information available on the effect of high temperature on photosynthesis, however, is either concerned with long-term responses by which plants are able to modify their photosynthetic functions, increasing both their tolerance and thermal optimum for net CO, assimilation, or wit...

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“…But the existence of QB-non-reducing PS II units in leaves of various plants has been established (Chylla andWhitmarsh 1989, Ort andWhitmarsh 1990). According to Melis et al (1988, cf. Melis 1985, in spinach thylakoids the population of such units is identical with the PS-II/3 fraction.…”

Section: Discussionmentioning

confidence: 99%

“…For calculation of the photochemical yield, dpp, we assume for reasons of simplicity that all/3 units are of 'QB-non-reducing type' (see Melis et al 1988) and do not contribute to linear electron transport. Therefore, the rate constant k e in this case is ascribed only to the fraction ce • (1 -D'):…”

Section: Outline Of the Modelmentioning

confidence: 99%

A simple model relating photoinhibitory fluorescence quenching in chloroplasts to a population of altered Photosystem II reaction centers

Giersch

Krause

1991

Photosynth Res

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A model is presented describing the relationship between chlorophyll fluorescence quenching and photoinhibition of Photosystem (PS) II-dependent electron transport in chloroplasts. The model is based on the hypothesis that excess light creates a population of inhibited PS II units in the thylakoids. Those units are supposed to posses photochemically inactive reaction centers which convert excitation energy to heat and thereby quench variable fluorescence. If predominant photoinhibition of PS IIα and cooperativity in energy transfer between inhibited and active units are presumed, a quasi-linear correlation between PS II activity and the ratio of variable to maximum fluorescence, FVFM, is obtained. However, the simulation does not result in an inherent linearity of the relationship between quantum yield of PS II and FVFM ratio. The model is used to fit experimental data on photoinhibited isolated chloroplasts. Results are discussed in view of current hypotheses of photoinhibition.

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Photosystem II Heterogeneity in Chloroplasts

Cited by 14 publications

References 37 publications

Photoinhibition of photosynthesis in chilled potato leaves is not correlated with a loss of Photosystem-II activity

Photoinhibition of photosynthesis in chilled potato leaves is not correlated with a loss of Photosystem-II activity

Effect of High Temperature on Photosynthesis in Beans (I. Oxygen Evolution and Chlorophyll Fluorescence)

A simple model relating photoinhibitory fluorescence quenching in chloroplasts to a population of altered Photosystem II reaction centers

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