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  • Pisum  (3)
  • photoinhibition  (3)
  • Springer  (6)
  • Oxford University Press
  • 1
    Electronic Resource
    Electronic Resource
    Mechanistic differences in photoinhibition of sun and shade plants (1992)
    Springer
    Planta 188 (1992), S. 422-431 
    Details
    ISSN: 1432-2048
    Keywords: Light acclimation ; Photosynthesis ; Photoinhibition ; Photosystem II repair cycle ; Pisum ; Tradescantia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf discs of the shade plant Tradescantia albiflora Kunth grown at 50 μmol · m−2 · s−1, and the facultative sun/shade plant Pisum sativum L. grown at 50 or 300 μmol · m−2, s−1, were photoinhibited for 4 h in 1700 μmol photons m−2 · s−1 at 22° C. The effects of photoinhibition on the following parameters were studied: i) photosystem II (PSII) function; ii) amount of D1 protein in the PSII reaction centre; iii) dependence of photoinhibition and its recovery on chloroplast-encoded protein synthesis; and, iv) the sensitivity of photosynthesis to photoinhibition in the presence or absence of the carotenoid zeaxanthin. We show that: i) despite different sensitivities to photoinhibition, photoinhibition in all three plants occurred at the reaction centre of PSII; ii) there was no correlation between the extent of photoinhibition and the degradation of the D1 protein; iii) the susceptibility to photoinhibition by blockage of chloroplas-tencoded protein synthesis was much less in shade plants than in plants acclimated to higher light; and iv) inhibition of zeaxanthin formation increased the sensitivity to photoinhibition in pea, but not in the shade plant Tradescantia. We suggest that there are mechanistic differences in photoinhibition of sun and shade plants. In sun plants, an active repair cycle of PSII replaces photoinhibited reaction centres with photochemically active ones, thereby conferring partial protection against photoinhibition. However, in shade plants, this repair cycle is less important for protection against photoinhibition; instead, photoinhibited PSII reaction centres may confer, as they accumulate, increased protection of the remaining connected, functional PSII centres by controlled, nonphotochemical dissipation of excess excitation energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192810
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  • 2
    Electronic Resource
    Electronic Resource
    Light inactivation of functional photosystem II in leaves of peas grown in moderate light depends on photon exposure (1995)
    Springer
    Planta 196 (1995), S. 401-411 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; D1 protein ; Photoinhibition ; Photoprotection ; Photosystem II heterogeneity ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To determine the dependence of in vivo photosystem (PS) II function on photon exposure and to assign the relative importance of some photoprotective strategies of PSII against excess light, the maximal photochemical efficiency of PSII (Fv/Fm) and the content of functional PSII complexes (measured by repetitive flash yield of oxygen evolution) were determined in leaves of pea (Pisum satlvum L.) grown in moderate light. The modulation of PSII functionality in vivo was induced by varying either the duration (from 0 to 3 h) of light treatment (fixed at 1200 or 1800 μmol photons · m-2 · s-1) or irradiance (from 0 to 3000 μmol photons · m-2 · s-1) at a fixed duration (1 h) after infiltration of leaves with water (control), lincomycin (an inhibitor of chloroplast-encoded protein synthesis), nigericin (an uncoupler), or dithiothreitol (an inhibitor of the xanthophyll cycle) through the cut petioles of leaves of 22 to 24-day-old plants. We observed a reciprocity of irradiance and duration of illumination for PSII function, demonstrating that inactivation of functional PSII depends on the total number of photons absorbed, not on the rate of photon absorption. The Fv/Fm ratios from photoinhibitory light-treated leaves, with or without inhibitors, declined pseudo-linearly with photon exposure. The number of functional PSII complexes declined multiphasically with increasing photon exposure, in the following decreasing order of inhibitor effect: lincomycin 〉 nigericin 〉 DTT, indicating the central role of D1 protein turnover. While functional PSII and Fv/Fm ratio showed a linear relationship under high photon exposure conditions, in inhibitor-treated leaves the Fv/Fm ratio failed to reveal the loss of up to 25% of the total functional PSII under low photon exposure. The loss of this 25% of less-stable functional PSII was accompanied by a decrease of excitation-energy trapping capacity at the reaction centre of PSII (revealed by the fluorescence parameter, 1/Fo-1/Fm, where Fo and Fm stand for chlorophyll fluorescence when PSII reaction centres are open and closed, respectively), but not by a loss of excitation energy at the antenna (revealed by the fluorescence parameter, 1/Fm). We conclude that (i) PSII is an intrinsic photon counter under photoinhibitory conditions, (ii) PSII functionality is mainly regulated by D1 protein turnover, and to a lesser extent, by events mediated via the transthylakoid pH gradient, and (iii) peas exhibit PSII heterogeneity in terms of functional stability during photon exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203636
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  • 3
    Electronic Resource
    Electronic Resource
    Photoinactivation of functional photosystem II and D1-protein synthesis in vivo are independent of the modulation of the photosynthetic apparatus by growth irradiance (1996)
    Springer
    Planta 198 (1996), S. 300-309 
    Details
    ISSN: 1432-2048
    Keywords: D1-protein ; Photoinhibition ; Photon exposure ; Photosystem II heterogeneity ; Light acclimation ; Pisum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate whether the in-vivo photoinhibition of photosystem II (PSII) function by excess light is an intrinsic property of PSII, the maximal photochemical efficiency of PSII (Fv/Fm) and the content of functional PSII (measured by repetitive flash yield of oxygen evolution) were determined in leaves of pea (Pisum sativum L.), grown in 50 (low light), 250 (medium light), and 650 (high light) μmol photons·m−2·s−1. The modulation of PSII functionality in vivo was induced in 1.1% CO2 by varying either (i) the duration (0–2 h) of light treatment (fixed at 1800 μmol photons· m−2·s−1) or (ii) irradiance (0–3200 μmol photons·m−2·s−1) at a fixed duration (1 h), after infiltration of leaves with water (control), lincomycin (an inhibitor of chloroplast-encoded protein synthesis), or a combination of lincomycin with nigericin (an uncoupler), through the cut petioles of leaves of 22-to 24-d-old plants. The reciprocity law of irradiance and duration of illumination for PSII function in vivo (Park et al. 1995, Planta 196: 401–411) holds in all differently light-grown peas, demonstrating that inactivation of functional PSII depends on photon exposure (mol photons·m−2), not on the rate of photon absorption. In vivo, PSII acts as an intrinsic “photon counter” and at higher photon exposures is inactivated following absorption of about 3 × 107 photons. There is a functional heterogeneity of PSII in vivo with 25% less-stable PSIIs that are inactivated at low photon exposure, compared to 75% more-stable PSIIs regardless of modulation of the photosynthetic apparatus. We suggest that the less-stable PSIIs represent monomers located in the nonappressed granal margins, while the more-stable PSIIs are dimers located in the appressed grana membrane cores. The capacity for D1-protein synthesis was the same in all the light-acclimated peas and saturated at low light, indicating that D1-protein repair is also an intrinsic property of PSII. This accounts for the low intensity required for recovery of photoinhibition in sun and shade plants which is independent of light-harvesting antennae size or PSII/PSI stoichiometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206257
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  • 4
    Electronic Resource
    Electronic Resource
    Photosystem II function and herbicide binding sites during photoinhibition of spinach chloroplasts in-vivo and in-vitro (1989)
    Springer
    Photosynthesis research 21 (1989), S. 17-26 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; herbicide binding ; photoinhibition ; photosynthesis ; photosystem II ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The time courses of some Photosystem II (PS II) parameters have been monitored during in-vivo and in-vitro photoinhibition of spinach chloroplasts, at room temperature and at 10 °C or 0 °C. Exposing leaf discs of low-light grown spinach at 25 °C to high light led to photoinhibition of chloroplasts in-vivo as manifested by a parallel decrease in the number of functional PS II centres, the variable chlorophyll fluorescence at 77K (F v /F m ), and the number of atrazine-binding sites. When the photoinhibitory treatment was given at 10 °C, the former two parameters declined in parallel but the loss of atrazine-binding sites occurred more slowly and to a lesser extent. During in-vitro photoinhibition of chloroplast thylakoids at 25 °C, the loss of functional PS II centres proceeded slightly more rapidly than the loss of atrazine-binding sites, and this difference in rate was further increased when the thylakoids were photoinhibited at 0 °C. During the recovery phase of leaf discs (up to 9 h) the increases in F v /F m preceded that of the number of functional PS II centres, while only a further decline in the number of atrazine-binding sites was observed. The recovery of variable chlorophyll fluorescence and the concentration of functional PS II centres occurred more rapidly at 25 °C than at 10 °C. These results suggest that the photoinhibition of PS II function is a relatively temperature-independent early photochemical event, whereas the changes in the concentration of herbicide-binding sites appear to be a more complex biochemical process which can occur with a delayed time course.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047171
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  • 5
    Electronic Resource
    Electronic Resource
    Unifying model for the photoinactivation of Photosystem II in vivo under steady-state photosynthesis (1998)
    Springer
    Photosynthesis research 56 (1998), S. 1-13 
    Details
    ISSN: 1573-5079
    Keywords: photoinhibition ; Photosystem II ; primary radical pair ; singlet oxygen ; triplet P680
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present a unifying mechanism for photoinhibition based on current obsevations from in vivo studies rather than from in vitro studies with isolated thylakoids or PS II membranes. In vitro studies have limited relevance for in vivo photoinhibition because very high light is used with photon exposures rarely encountered in nature, and most of the multiple, interacting, protective strategies of PS II regulation in living cells are not functional. It is now established that the photoinactivation of Photosystem II in vivo is a probability and light-dosage event which depends on the photons absorbed and not the irradiance per se. As the reciprocity law is obeyed and target theory analysis strongly suggests that only one photon is required, we propose that a single dominant molecular mechanism occurs in vivo with one photon inactivating PS II under limiting, saturating or sustained high light. Two mechanisms have been proposed for photoinhibition under high light, acceptor-side and donor-side photoinhibition [see Aro et al. (1994) Biochim Biophys Acta 1143: 113–134], and another mechanism for very low light, the low-light syndrome [Keren et al. (1995) J Biol Chem 270: 806–814]. Based on the exciton-radical pair equilibrium model of exciton dynamics, we propose a unifying mechanism for the photoinactivation of PS II in vivo under steady-state photosynthesis that depends on the generation and maintenance of increased concentrations of the primary radical pair, P680+Pheo−, and the different ways charge recombination is regulated under varying environmental conditions [Anderson et al. (1997) Physiol Plant 100: 214–223]. We suggest that the primary cause of damage to D1 protein is P680+, rather than singlet O2 formed from triplet P680, or other reactive oxygen species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005946808488
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  • 6
    Electronic Resource
    Electronic Resource
    Photoinactivation of photosystem II by cumulative exposure to short light pulses during the induction period of photosynthesis (1996)
    Springer
    Photosynthesis research 47 (1996), S. 51-59 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; photoinhibition ; photon exposure ; photosynthetic induction ; susceptibility to light stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinactivation of Photosystem (PS) II in vivo was investigated by cumulative exposure of pea, rice and spinach leaves to light pulses of variable duration from 2 to 100 s, separated by dark intervals of 30 min. During each light pulse, photosynthetic induction occurred to an extent depending on the time of illumination, but steady-state photosynthesis had not been achieved. During photosynthetic induction, it is clearly demonstrated that reciprocity of irradiance and duration of illumination did not hold: hence the same cumulative photon exposure (mol m−2) does not necessarily give the same extent of photoinactivation of PS II. This contrasts with the situation of steady-state photosynthesis where the photoinactivation of PS II exhibited reciprocity of irradiance and duration of illumination (Park et al. (1995) Planta 196: 401–411). We suggest that, for reciprocity to hold between irradiance and duration of illumination, there must be a balance between photochemical (qP) and non-photochemical (NPQ) quenching at all irradiances. The index of susceptibility to light stress, which represents an intrinsic ability of PS II to balance photochemical and non-photochemical quenching, is defined by the quotient (1-qP)/NPQ. Although constant in steady-state photosynthesis under a wide range of irradiance (Park et al. (1995). Plant Cell Physiol 36: 1163–1169), this index of susceptibility for spinach leaves declined extremely rapidly during photosynthetic induction at a given irradiance, and, at a given cumulative photon exposure, was dependent on irradiance. During photosynthetic induction, only limited photoprotective strategies are developed: while the transthylakoid pH gradient conferred some degree of photoprotection, neither D1 protein turnover nor the xanthophyll cycle was operative. Thus, PS II is more easily photoinactivated during photosynthetic induction, a phenomenon that may have relevance for understorey leaves experiencing infrequent, short sunflecks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017753
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