Characterisation of the effects of Antimycin A upon high energy state quenching of chlorophyll fluorescence (qE) in spinach and pea chloroplasts

High energy state quenching of chlorophyll fluorescence (qE) is inhibited by low concentrations of the inhibitor antimycin A in intact and osmotically shocked chloroplasts isolated from spinach and pea plants. This inhibition is independent of any effect upon pH (as measured by 9-aminoacridine fluorescence quenching). A dual control of qE formation, by pH and the redox state of an unidentified chloroplast component, is implied. Results are discussed in terms of a role for qE in the dissipation of excess excitation energy within photosystem II.Abbreviations 9-AA_max = Maximum yield of 9-aminoacridine fluorescence - DCMU = 3(3,4-dichlorophenyl)-1,1-dimethylurea; F_max ± Maximum yield of chlorophyll fluorescence - hr = hour - PAR = Photosynthetically Active Radiation - Q_A = Primary stable electron acceptor within photosystem II - qE = High energy state quenching of chlorophyll fluorescence - qI = quenching of chlorophyll fluorescence related to photoinhibition - qP = Quenching of chlorophyll fluorescence by oxidised plastoquinone - qQ = photochemical quenching of chlorophyll fluorescence - qR = (F_max—maximum level of chlorophyll fluorescence induced by the addition of saturating DCMU) - qT = Quenching of chlorophyll fluorescence attributable to state transitions     

Primary Events, Energy Transfer, and Reactions in Photosynthetic Units: Photon Trapping in Photosystem II of Photosynthesis: The Fluorescence Rise Curve in the Presence of 3-(3,4-Dichlorophenyl)-1,1-dimethylurea

Using isolated chloroplasts in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an analysis was made of the rise of the fluorescence yield effected by weak light. Depending on the pretreatment, the time-course of the rapid photochemical part of the rise varied between nearly first-order and quadratic kinetics, i.e., reflected either a one-quantum or a two-quantum conversion. We consider the occurrence of two photoreductants per system II unit, which are reoxidized in different dark reactions. The data further showed that the “first-order process” is also inhomogeneous.     

The Photochemical Activity of Chloroplasts and Subchloroplast Particles Isolated from Etiolated Bean Leaves Exposed to Continuous Light

The photochemical activity of chloroplasts and subchloroplastparticles isolated from primary bean leaves between the 4thand 24th hour of illumination of etiolated seedlings is thesubject of this paper. The photosystem I activity (oxygen uptakein the presence of MV, DCIP, ascorbate and DCMU), expressedon a unit chlorophyll basis, decreased approximately 10-foldbetween 4 and 8 h of greening. At the same time the photosystemII activity (DCIP photoreduction in the presence of DPC) wasreduced to a half. The photosystem I activity also decreasedin all hitherto investigated fractions which were isolated fromthe digitonin-treated chloroplasts. However, at the initialphase of greening this decrease was the most significant inthe fraction containing heavy particles. After 24 h of greening DCMU, at concentrations higher than 10^–10M, limited the rate of ferricyanide photoreduction by isolatedchloroplasts, whereas after 6 h of greening this effect wasobservable even in the presence of 10^–12 M DCMU. The resultsobtained demonstrated that under those conditions both photosystemswere active after 4 h of greening and PS I activity developedmore rapidly than that of PS II. It also follows from the presenteddata that the water splitting reactions were delayed in developmentas compared to the other reactions investigated, and that PSII units may limit the electron flow in chloroplasts at earlierstages of leaf greening.     

Primary Events, Energy Transfer, and Reactions in Photosynthetic Units: The Ratio between Delayed Light and Fluorescence Emitted by Chloroplasts

Electric fields of a few hundred volts per centimeter greatly stimulate the emission of delayed light from “broken” chloroplasts. At low intensities of exciting light the fluorescence of these chloroplasts is also stimulated by the electric field, but to a lesser extent. Assuming that the electric field has no effect on prompt fluorescence, and has the same effect on the delayed light emission during illumination as in the dark, we can determine the ratio of delayed light to fluorescence under steady-state illumination.     

On the possible site of inhibition of photosynthetic electron transport by ultraviolet-B (UV-B) radiation

In Amaranthus chloroplasts that are exposed to ultraviolet-B (UV-B) radiation, the electron flow from water to dichlorophenol indophenol (DCPIP) was inhibited, but the electron flow from reduced DCPIP to methyl viologen remains unaffected. Diphenylcarbazide was ineffective in restoring the activity of DCPIP Hill reaction in UV-B irradiated chloroplasts. Electron flow from water to ferricyanide or dichloro-dimethoxy- p -benzoquinone was inhibited to a degree similar to that of the DCPIP Hill reaction.
The rate of carotenoid photobleaching in the presence of carbonyl cyanide- m -chlorophenylhydrazone, an indicator of the photochemical reaction near the vicinity of reaction centre of photosystem II, was suppressed and paralleled with the inhibition of the DCPIP Hill reaction.
In the UV-B treated chloroplasts, the variable part of the fluorescence transient was diminished. Though the fluorescence yield was lowered by the UV-B radiation, addition of 3-(3,4-dichlorophenyl)-l, l-dimethylurea (DCMU) and/or sodium dithionite increased the emission markedly. With the increase in the dosage of UV-B irradiation, the time required to reach the steady state fluorescence level became longer in the absence of DCMU and shorter in the presence of DCMU. The kinetics of 520 nm absorbance change was markedly unaltered by the UV-B irradiation but its dark decay was prolonged. It is concluded that UV-B irradiation inactivates the photosystem II reaction centre.     

The emission yields of delayed and prompt fluorescence from chloroplasts.

1. The decay of delayed fluorescence from chloroplasts blocked with 3-(3,4-dichlorophenyl)-1,1-dimethylurea and uncoupled with gramicidin has been measured in the time range 0.75--45 ms by use of a laser phosphoroscope. 2. The decays have been analysed as the sum of three first-order components of approximate half-lives 0.2, 2.5 and 300 ms by a computer-assisted least-squares fit procedure. 3. The prompt fluorescence yield of the chloroplasts was manipulated by changing the cation concentration of the chloroplast-suspending medium. 4. Analysis of the concentration dependence of the components of the delayed fluorescence decay and of the prompt fluorescence inductions indicates that the emission yield of the intermediate (tau approximately 2.5 ms) component of the decay is equal to the fluorescence yield of a Photosystem II photosynthetic unit with an open trap, and that for the slow (tau approximately 300 ms) component the emission yield is equal to the total Photosystem II prompt fluorescence yield. 5. It is concluded that the delayed fluorescence yield in the time range studied is a complex function of time, which may be due to there being different mechanisms leading to delayed fluorescence production at short and long times after cessation of illumination.     

Induction patterns of delayed luminescence from isolated chloroplasts. I. Response of delayed luminescence to changes in the prompt fluorescence yield

1. Using a phosphoroscope, delayed luminescence and prompt chlorophyll fluorescence from isolated chloroplasts have been compared during the induction period.2. Two distinct decay components of delayed luminescence were measured a “fast” component (from ≈1 ms to ≈6 ms) and a “slow” component (at ≈6 ms).3. The fast luminescence component often did not correlate with the fluorescence changes while the slow component significantly changed its intensity during the induction period in a manner which could usually be linearly correlated with variable portion of the fluorescence yield change.4. This correlation was evident after preillumination with far-red light or after allowing a considerable time for dark relaxation.5. The close relationship between the slow luminescence component and variable fluorescence yield was observed with a large range of light intensities and also in the presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea which considerably changes the fluorescence induction kinetics.6. Valinomycin and other antibiotics reduced the amplitude of the 6 ms (slow) luminescence without affecting its relation with the fluorescence induction suggesting possibly that a constant electrical gradient exist in the dark or formed very rapidly in the light, which effects the emission intensity.7. Changes in salt levels of suspending media equally affected the amplitude of both delayed luminescence and variable fluorescence under conditions when the reduction of Q is maximal and constant.8. The results are discussed in terms of several models. It is concluded that the model of independent Photosystem II units together with photosynthetic back reaction concept is incompatible with the data. Other alternative models (the “lake” model and photosynthetic back reaction; recombination of charges in the antenna chlorophyll; the “W” hypothesis) were in closer agreement with the results.     

Restoration by silicotungstic acid of DCMU-inhibited photoreactions in spinach chloroplasts

The restoration by silicotungstic acid of the reversible light-induced pH rise mediated by pyocyanine in EDTA-treated chloroplasts corresponds to an irreversible fixation of the acid. The proton uptake is linearly related to the amount of fixed acid (4 protons per molecule of acid) as long as the amount of silicotungstic acid does not exceed 200 nmoles/mg of chlorophyll.In the same conditions silicotungstic acid partly restores ferricyanide reduction and O₂ evolution in chloroplasts suspensions supplemented with DCMU. These photoreactions are observed only with chloroplasts and these chloroplasts must have an unimpaired water-splitting mechanism.Silicotungstic acid does not impair DCMU fixation on the specific sites. More likely in its presence the properties of the membrane change and ferricyanide can accept electrons from a part of the electron transport chain, between the Photosystem II reaction center and the block of the electron flow by DCMU.     

Primary Events, Energy Transfer, and Reactions in Photosynthetic Units: A Connected Model of the Photosynthetic Unit

The concept of photosynthetic unit (PSU) is reviewed in the light of the authors' results in the fields of fluorescence and luminescence (delayed light). Models of PSU are mainly distinguished by the amount of exciton exchange which is allowed between units. The “separate” model, with its “first-order” character, is not consistent with fluorescence kinetic data. The sigmoidal rise of fluorescence under actinic light is best explained by “nonseparate” models; however, most of these models assume a delocalization of excitons or centers. The “connected” model introduced here is not subject to this criticism. It discloses a new effect (the “îlot” effect): a nonrandom grouping of fluorescent units the consequences of which are discussed. It is noted that a “two-quantum” model for the photochemical reaction gives results very similar to those of the connected model. A relation between luminescence intensity and fluorescence yield is seen as a necessary consequence of the PSU concept. Its meaning is different in separate and nonseparate models. This relation is discussed in connection with the true system II fluorescence emission.     

Effects of trypsin and cations on chloroplast membranes

A mild tryptic digestion of chloroplast membranes eliminates the effects of saturating concentrations of cations (3 to 5 millimolar MgCl₂) on chlorophyll fluorescence yield, membrane stacking, and photosystem II photochemical efficiency in spinach. At the same time, the negative surface potential of the membranes is increased (by trypsin) as revealed by studies with 9-aminoacridine. High concentrations of cations (25 to 100 millimolar MgCl₂) added after trypsin digestion are effective in restoring high fluorescence yields and membrane stacking. High concentrations of cations added after trypsin treatment do not increase the photosystem II efficiency. It is concluded that the “diffuse electrical layer” hypothesis of Barber et al. (Barber J, J Mills, A Love, 1977 FEBS Lett 74: 174-181) satisfactorily explains the effect of trypsin in eliminating the influence of saturating concentrations of cations on chlorophyll fluorescence yield and membrane stacking. However, the effect on photosystem II photochemical efficiency seems to require another mechanism.     

Analysis of chlorophyll a fluoresence changes in weak light in heat treated Amaranthus chloroplasts

After preheating of Amaranthus chloroplasts at elevated temperatures (up to 45°C), the chlorophyll a fluorescence level under low excitation light rises as compared to control (unheated) as observed earlier in other chloroplasts (Schreiber U and Armond PA (1978) Biochim Biophys Acta 502: 138–151). This elevation of heat induced fluorescence yield is quenched by addition of 0.1 mM potassium ferricyanide, suggesting that with mild heat stress the primary electron acceptor of photosystem II is more easily reduced than the unheated samples. Furthermore, the level of fluorescence attained after illumination of dithionite-treated samples is independent of preheating (up to 45°C). Thus, these experiments indicate that the heat induced rise of fluorescence level at low light can not be due to changes in the elevation in the true constant F₀ level, that must by definition, be independent of the concentration of Q_A. It is supposed that the increase in the fluorescence level by weak modulated light is either partly associated with dark reduction of Q_A due to exposure of chloroplasts to elevated temperature or due to temperature induced fluorescence rise in the so called inactive photosystem II centre where Q_A are not connected to plastoquinone pool. In the presence of dichlorophenyldimethylurea the fluorescence level triggered by weak modulated light increases at alkaline pH, both in control and heat stressed chloroplasts. This result suggests that the alkaline pH accelerates electron donation from secondary electron donor of photosystem II to Q_A both in control and heat stressed samples. Thus the increase in fluorescence level probed by weak modulated light due to preheating is not solely linked to increase in true F₀ level, but largely associated with the shift in the redox state of Q_A, the primary stable electron acceptor of photosystem II.Abbreviations ADRY Acceleration of Deactivation of Reaction of Enzyme Y - CCCP Carbonyl cyanide 4-(trifluoromethoxy)-phenylhydrazone - Chl Chlorophyll - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - FeCN potassium ferricyanide - HEPES 4-(2-hydroxy ethyl)-1-piperazine ethane sulfonic acid - LHCP Light harvesting chlorophyll protein - MES (4-morpholine ethane sulfonic acid) - PS photosystem - Q_A and Q_B first and second consecutive electron acceptors of photosystem II - TES (2-[tris(hydroxymethyl)-methylamino]-1-ethanesulfonic acid) sulfonic acid - TRICINE N-[tris(hydroxymethyl)methyl] glycine     

Inhibition of O2 evolution by NADP in isolated potato tuber chloroplast and its identity with 3-(3,4-dichlorophenyl)-1,1-dimethyl urea inhibition site.

Chloroplast from greening potato tuber showed good photosynthetic capacity. The evolution of O₂ was dependent upon the intensity of light. A light intensity of 30 lux gave maximum O₂ evolution. At higher intensities inhibition was observed. The presence of bicarbonate in the reaction mixture was essential for O₂ evolution. NADP was found to be a potent inhibitor of O₂ evolution in this system. NADP and 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) inhibited the O₂ evolution completely at a 3 μm concentration level, which was reversed by oxidized 2,6-dichlorophenol-indophenol (DCIP). Cyanide (CN)-treated chloroplasts showed full O₂ evolution capacity, when a lipophilic electron acceptor like N-tetramethyl-p-phenylenediamine (TMPD) or DCIP was used along with ferricyanide. Ferricyanide alone showed only 20% reduction. NADP or DCMU could inhibit O₂ evolution only when TMPD was the acceptor but not with DCIP. Photosystem II (PS II) isolated from these chloroplasts also showed inhibition by NADP or DCMU and its reversal by DCIP. Here also the evolution of O₂ with only TMPD as acceptor was sensitive to NADP or DCMU. In the presence of added silicotungstate in PS II NADP or DCMU did not affect ferricyanide reduction or oxygen evolution. The chloroplasts were able to bind exogenously added NADP to the extent of 120 nmol/mg chlorophyll. It is concluded that the site of inhibition of NADP is the same as in DCMU, and it is between the DCIP and TMPD acceptor site in the electron transport from the quencher (Q) to plastoquinone (PQ).     

A differential effect of 3-(3′4′ dichlorophenyl)-1,1 dimethyl urea and atrazine on fluorescence kinetics in chloroplasts

It was found that DCMU had a differential effect at two concentration ranges on variable fluorescence kinetics in isolated chloroplasts. The increase in fluorescence rate at low concentrations of DCMU was abolished by preincubation of chloroplasts with ferricyanide or formate, treatments which were shown to convert Fe in the PS II reaction center (i.e., the FeQ_A complex) into a non-oxidizable form, but it was not affected by Tris treatment. Increase in fluorescence kinetics (at the initial linear rate) at high concentrations of DCMU was found to be abolished by Tris treatment but it was only marginally affected by ferricyanide or formate treatments. The effect of Tris could be abolished by addition of hydroquinone-ascorbate, which restored electron flow to the pool of secondary acceptors.Contrary to the effect of DCMU, no such differential concentration dependence of the variable fluorescence kinetics was found for atrazine.The increase in fluorescence kinetics (at the initial linear rate) at a low concentration rate of DCMU is presumably restricted to units which contain an oxidizable Fe in the FeQ_A complex. Increase in fluorescence kinetics (at the initial linear rate) at high DCMU concentration is probably related to the effect of DCMU at the Q_B site.Abbreviations DCMU 3-(34 dichlorophenyl)-1,1 dimethyl urea - PS II Photosystem II - Tris tris (hydroxymethyl) aminomethane     

Fluorescence and Delayed Light Emission from Mesophyll and Bundle Sheath Cells in Leaves of Normal and Salt-Treated Panicum miliaceum

A modified fluorescence microscope system was used to measure chlorophyll fluorescence and delayed light emission from mesophyll and bundle sheath cells in situ in fresh-cut sections from leaves of Panicum miliaceum L. The fluorescence rise in 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU)-treated leaves and the slow fluorescence kinetics in untreated leaves show that mesophyll chloroplasts have larger photosystem II unit sizes than do bundle sheath chloroplasts. The larger photosystem II units imply more efficient noncyclic electron transport in mesophyll chloroplasts. Quenching of slow fluorescence also differs between the cell types with mesophyll chloroplasts showing complex kinetics and bundle sheath chloroplasts showing a relatively simple decline. Properties of the photosynthetic system were also investigated in leaves from plants grown in soil containing elevated NaCl levels. As judged by changes in both fluorescence kinetics in DCMU-treated leaves and delayed light emission in leaves not exposed to DCMU, salinity altered photosystem II in bundle sheath cells but not in mesophyll cells. This result may indicate different ionic distributions in the two cell types or, alternatively, different responses of the two chloroplast types to environmental change.     

Site of salicylaldoxime interaction with photosystem II

The reversible inhibition of Photosystem II by salicylaldoxime was studied in spinach D-10 particles by fluorescence, optical absorption, and electron spin resonance spectroscopy. In the presence of 15 mM salicylaldoxime, the initial fluorescence yield was raised to the level of the maximum fluorescence, indicating efficient charge recombination between reduced pheophytin (Ph) and P680⁺. In agreement with the rapid (ns) backreaction expected between Ph^– and P680⁺, the optical absorption transient at 820 mm was not observed. When the particles were washed free of salicylaldoxime, the optical absorption transient resulting from the rereduction of P680⁺ was restored to the µs timescale. These results, along with the previously observed inhibition of electron transport reactions and diminution of the 515-nm absorption change in chloroplasts [Golbeck, J.H. (1980) Arch Biochem Biophys 202, 458–466], are consistent with a site of inhibition between Ph and QA in Photosystem II. ESR Signal IIf and Signal Its were abolished in the presence of 25 mM salicylaldoxime, but both signals could be recovered by washing the D-10 particles free of the inhibitor. The loss of Signal Ilf is most likely a consequence of the inhibition between Ph and Q_A; the rapid charge recombination between Ph^– and P680⁺ would preclude electron transfer from an electron donor on the oxidizing side of Photosystem II. The loss of Signal Its may be due to a change in the environment of the donor complex such that the semiquinone radical giving rise to Signal Its interacts with a nearby reductant.Abbreviations D₁ electron donor to P680⁺ in oxygen-inhibited chloroplasts - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - F₀ prompt chlorophyll a fluorescence yield - F_i initial chlorophyll a fluorescence yield - F_max maximum chlorophyll a fluorescence yield - F_var variable chlorophyll a fluorescence yield - FWHM full width at half maximum - Mes 2-(N-morpholino) ethanesulfonic acid - P680 reaction center chlorophyll a of photosystem II - Ph pheophytin intermediate electron acceptor - Q_A primary quinone electron acceptor - Q_B secondary quinone electron acceptor - Tris tris(hydroxymethyl)aminomethane - Z electron donor to P680⁺     

Delayed fluorescence in photosynthesis

Photosynthesis is a very efficient photochemical process. Nevertheless, plants emit some of the absorbed energy as light quanta. This luminescence is emitted, predominantly, by excited chlorophyll a molecules in the light-harvesting antenna, associated with Photosystem II (PS II) reaction centers. The emission that occurs before the utilization of the excitation energy in the primary photochemical reaction is called prompt fluorescence. Light emission can also be observed from repopulated excited chlorophylls as a result of recombination of the charge pairs. In this case, some time-dependent redox reactions occur before the excitation of the chlorophyll. This delays the light emission and provides the name for this phenomenon—delayed fluorescence (DF), or delayed light emission (DLE). The DF intensity is a decreasing polyphasic function of the time after illumination, which reflects the kinetics of electron transport reactions both on the (electron) donor and the (electron) acceptor sides of PS II. Two main experimental approaches are used for DF measurements: (a) recording of the DF decay in the dark after a single turnover flash or after continuous light excitation and (b) recording of the DF intensity during light adaptation of the photosynthesizing samples (induction curves), following a period of darkness. In this paper we review historical data on DF research and recent advances in the understanding of the relation between the delayed fluorescence and specific reactions in PS II. An experimental method for simultaneous recording of the induction transients of prompt and delayed chlorophyll fluorescence and decay curves of DF in the millisecond time domain is discussed.     

Studies on thermoluminescence,delayed light emission and oxygen evolution from photosynthetic materials: UV effects

The effect of ultraviolet light on thermoluminescence, oxygen evolution and the slow component of delayed light has been investigated in chloroplasts and Pothos leaves. All peaks including peak V (48°C) were inhibited by UV. However, the peak at 48°C which was induced by DCMU was enhanced following UV irradiation of chloroplasts at ambient temperature (23°C) whereas peak II (-12°C) and peak III (10°C) which were also induced by DCMU were inhibited. Chloroplasts treated with DCMU and dark incubated for several minutes at ambient temperature prior to recording of glow curves have also shown enhancement of peak at 48°C. A slow component of delayed light and photosystem II activity of chloroplasts were inhibited by UV whereas photosystem I activity was marginally affected. These results corroborate involvement of photosystem II in generating thermoluminescence and slow components of delayed light in photosynthetic materials.Abbreviations DCIP Dichlorophenol Indophenol - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DCQ 2,6 Dichloro-p-benzoquinone - DLE delayed light emission - MOPS Morpholino propane sulfonic acid - PSI Photosystem I - PS II Photosystem II - TL thermoluminescence     

Temperature dependence of chlorophyll a fluorescence in relation to the physical phase of membrane lipids algae and higher plants

The temperature dependence of the yield of chlorophyll a fluorescence was measured at room temperatures in living algal cells and higher plant chloroplasts. 3-(3′,4′-Dichlorophenyl)-1, 1-dimethylurea was added to the samples during the measurements in order to eliminate the influence of photosynthetic photochemical reactions on the fluorescence yield.     

Induction of photochemical and non-photochemical quenching of chlorophyll fluorescence by low concentrations of m-dinitrobenzene

Chlorophyll fluorescence quenching induced by low concentrations of m-dinitrobenzene (DNB) is investigated. In intact spinach chloroplasts DNB causes photochemical and non-photochemical quenching. The two forms of quenching are distinguished by applying the saturation pulse method with a new type of modulation fluorometer. Half-maximal photochemical quenching is observed at about 3 micromolar DNB. It is inhibited by 3-(3,4 dichlorophenyl)-1, 1-dimethylurea (DCMU) and by 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB). Photochemical quenching by DNB leads to suppression of the I-P transient in a fluorescence induction curve. Upon application of saturating continuous light, the increase of fluorescence yield is separated into a photochemical and a thermal part. DNB causes suppression of only the slowest sub-component of the thermal part, in analogy to the action of Hill reagents. Simultaneous measurements of oxygen exchange rate and fluorescence reveal that a part of DNB induced quenching is accompanied by oxygen uptake. Most DNB-induced non-photochemical quenching is prevented by nigericin and, hence, can be considered energy-dependent quenching. The small component persisting in the presence of nigericin is identical to the one observed with methylviologen and other Hill reagents, likely to be due to static quenching by oxidized plastoquinone. The presented data confirm the original finding of Etienne and Lavergne (Biochim Biophys Acta 283: 268–278, 1972) that low concentrations of DNB selectively affect the thermal component of variable fluorescence. However, while these authors interpreted the quenching by a non-photochemical mechanism, the present investigation emphasizes a photochemical mechanism, in analogy to the effect of electron acceptors or mediators.Abbreviations DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCMU 3-(3,4-dichlorophenyl)-1, 1-dimethylurea - DNB m-dinitrobenzene - PGA 3-phosphoglycerate - PMS phenazinemethosulphate - PS I and PS II photosystems I and II