Estimation of the light distribution between photosystems I and II in intact wheat leaves by fluorescence and photoacoustic measurements

Malkin, Shmuel; Morgan, Colin; Austin, R. B.

doi:10.1007/bf00014679

Cited by 9 publications

(7 citation statements)

References 22 publications

(35 reference statements)

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“…This value is in accordance with a 1:1 stoichiometry of PS II and PSI when the chlorophyll a:b ratio is 2.9 [16]. Direct measurements of a on a range of Triticum genotypes gave values averaging 0.55 [14]. Thirdly, it is assumed that the I.t law [13] holds on the range of values of I used.…”

Section: Discussionmentioning

confidence: 54%

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Analysis of fluorescence transients of DCMU-treated leaves of Triticum species to provide estimates of the densities of photosystem II reaction centres

Morgan

Austin

1986

Photosynth Res

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The fluorescence of the chlorophyll associated with photosystem II was studied in seedling and flag leaves of Triticum species. Seedling leaves of the diploid species T. urartu had higher values of t (the normalised area over the fluorescence induction curve of DCMU treated leaves) than those of the other species studied which included hexaploid T. aestivum. However this difference was not evident when leaves were grown in a low light intensity (40 µmol quanta of photosynthetically active radiation m(-2) s(-1)). The smaller total number of chlorophyll molecules per photosystem II reaction centre (chl/RCII) in T. urartu (177) as compared with the other species (mean 234) was deduced from the observed differences in t. As a consequence of its lower chl/RCII, despite slightly lower chlorophyll content (mg m(-2)), T. urartu had a greater density of reaction centres than the other species (2880 cf 2230 nmol m(-2) of leaf). Consistent with the lower chl/RCII of T. urartu, it had a higher chlorophyll a/b ratio than the other genotypes. Seedling leaves of T. urartu had higher light saturated rates of photosynthesis than those of the other species, when grown at high light, a difference associated with reaction centre density.In flag leaves, when the complications due to variable development and senescence patterns were eliminated, t of the diploid species including T. urartu was lower than that of T. aestivum. The lower apparent chl/RCII of T. urartu arose partly because the molar extinction coefficient of the chlorophyll in the leaves of T. urartu was greater than in T. aestivum. However, the density of PS II reaction centres was slightly lower for the diploid species studied because their chlorophyll contents were lower than the hexaploids.The validity of the method for estimating chl/RCII from fluorescence transients is discussed. The possibility is considered that the difference in apparent chl/RCII of flag and seedling leaves of R. urartu as compared to the other five genotypes is a consequence of its different adaptive response to the spectral quality of the light.

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Section: Discussionmentioning

confidence: 54%

“…a = fraction of the light absorbed by chlorophyll which is distributed to PS II, assumed to be 0.5 [11,14]. and…”

Section: Fluorescence Inductionmentioning

confidence: 99%

Analysis of fluorescence transients of DCMU-treated leaves of Triticum species to provide estimates of the densities of photosystem II reaction centres

Morgan

Austin

1986

Photosynth Res

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“…troscopy (PAS), detected by Bell 1881, permits measurements of heat emission and has recently been ap-Light energy absorbed by the photosynthetic pigments plied to photosynthetic samples (Bults et al 1981, is used either to carry out photosynthesis or is emitted Buschmann andPrehn 1981, 1986, Buschmann et al as fluorescence and heat. Under optimum conditions of 1984, Malkin et al 1986). photosynthesis, fluorescence and heat emission are low;…”

Section: Introductionmentioning

confidence: 99%

Photoacoustic spectra of needles as an indicator of the activity of the photosynthetic apparatus of healthy and damaged conifers

Nagel

Buschmann

Lichtenthaler

1987

Physiologia Plantarum

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Photoacoustic spectra were measured at chopping frequencies of the excitation light at 22 and 515 Hz in order to detect differences between needles from healthy and damaged conifers (Abies alba Mill, and Picea abies Karst.) with respect to pigment distribution and possibly also to photosynthetic activity. Fully green needles of healthy trees exhibit photoacoustic spectra at 22 Hz with a maximum in the red absorption region of the chlorophyll. This maximum is lost with increasing damage to needles and chlorophyll breakdown. The photoacoustic spectra at 22 Hz of the damaged needles therefore are characterized by a higher signal in the blue‐light region as compared to that in the red‐light region. This can be quantified by forming the ratio of the photoacoustic signals at 675 and 475 nm (ratio PA 675/475). The needles of the damaged trees possess a lower photosynthetic activity, as seen from the CO2 fixation rate and the variable fluorescence (Rfd‐values). It is assumed that the changes in the PA‐spectra of the needles from damaged trees are the result of this decline of the photosynthetic apparatus and its function. In contrast to the PA‐spectrum at 22 Hz the PA‐spectra at 515 Hz, where the PA‐signals primarily emanate from the epidermal layer, exhibit a different shape with a maximum near 550 nm. In the needles from the damaged trees the PA‐signals are higher, particularly in this maximum range of the spectrum, than those of fully green needles from healthy trees.

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“…So far, only measurements of a qualitative nature have been made and these suggest that the efficiencies of both photosystems are similar in vivo (1). Any simple relationship between the quantum efficiency of PSI and PSII could be complicated due to cyclic flow around PSI, cyclic flow around PSII (10,17), an imbalance in the rate of excitation (9,22), and population size (24) of the reaction centers of both photosystems, inactive PSII centers, (12), and fluxes of electrons from the reducing side of PSII to 02 (4,23 …”

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Relationship between the Quantum Efficiencies of Photosystems I and II in Pea Leaves

Harbinson¹,

Genty²,

Baker³

1989

Plant Physiol.

175

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The irradiance dependence of the efficiencies of photosystems I and 11 were measured for two pea (Pisum sativum [L.]) varieties grown under cold conditions and one pea variety grown under warm conditions. The efficiencies of both photosystems declined with increasing irradiance for all plants, and the quantum efficiency of photosystem I electron transport was closely correlated with the quantum efficiency of photosystem 11 electron transport. In contrast to the consistent pattern shown by efficiency of the photosystems, the redox state of photosystem 11 (as estimated from the photochemical quenching coefficient of chlorophyll fluorescence) exhibited relationships with both irradiance and the reduction of P-700 that varied with growth environment and genotype. This variability is considered in the context of the modulation of photosystem 11 quantum efficiency by both photochemical and nonphotochemical quenching of excitation energy.The well established organization of the electron transport system of higher plant thylakoids implies a close coordination of the activities of PSI and PSII in linear electron flow (13,28). Although considerable efforts have been applied for the characterization of the detailed structure and functions of PSI and PSII, remarkably little attention has been given to the potential regulatory mechanisms needed to coordinate PSI and PSII activities. In this paper we examine the relationships between PSI and PSII photochemical activities in leaves using noninvasive spectroscopic techniques.Under conditions of increasing irradiance, the quantum efficiencies of both PSI and PSII decline. Oxidized P-7002 (p- 700+) is as good a quencher of excitation energy present in PSI as is reduced P-700 (P-700°) (25), but whereas quenching by P-7000 results in electron transport from PSI, quenching by P-700+ results only in thermal deactivation of the excitation energy. Consequently, the quantum efficiency of PSI is given by the degree of reduction of the P-700 pool (i.e. the amount of P-7000 relative to the total amount of P-700). Measurements of the redox state of P-700 in vivo have shown that the quantum efficiency of PSI is linearly related to the quantum efficiency for CO2 fixation when photorespiration is suppressed (28). With increasing irradiance the P-700 pool becomes progressively oxidized (15,16,28), and hence the quantum efficiency of PSI falls. The situation for PSII is complicated by the multiplicity of ways that PSII quantum efficiency can be modified (5, 16). The resolution of Chl fluorescence in vivo (which is largely from PSII) in terms of photochemical (qQ) and nonphotochemical quenching (qNp) has been described by Bradbury and Baker (3) and Deitz et al. (8). With increasing irradiance, qQ declines and qNP increases (8) but not in a way that can be simply related to the decline of 4PsHj (the quantum efficiency for electron transport by PSII) (29). Recently, Genty et al. ( 11) (Fv/Fm) (2,6,19).'The sequential arrangement of photosystems II and I in noncyclic electron transport (...

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Estimation of the light distribution between photosystems I and II in intact wheat leaves by fluorescence and photoacoustic measurements

Cited by 9 publications

References 22 publications

Analysis of fluorescence transients of DCMU-treated leaves of Triticum species to provide estimates of the densities of photosystem II reaction centres

Analysis of fluorescence transients of DCMU-treated leaves of Triticum species to provide estimates of the densities of photosystem II reaction centres

Photoacoustic spectra of needles as an indicator of the activity of the photosynthetic apparatus of healthy and damaged conifers

Relationship between the Quantum Efficiencies of Photosystems I and II in Pea Leaves

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