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  • 1
    Electronic Resource
    Electronic Resource
    Factors affecting akinete differentiation in Cylindrospermopsis raciborskii (Nostocales, Cyanobacteria) (2005)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 50 (2005), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Cylindrospermopsis raciborskii is a potentially toxic freshwater cyanobacterium which can produce akinetes (reproductive spores) that on germinating can contribute to future populations. To further understand factors controlling the formation of these specialised cells, the effects of diurnal temperature fluctuations (magnitude and frequency), in combination with different light intensities and phosphorus concentrations were investigated under laboratory conditions.2. Akinete differentiation was affected by the frequency of temperature fluctuations. Maximum akinete concentrations were observed in cultures that experienced multiple diurnal temperature fluctuations.3. Akinete concentrations increased with increasing magnitude of temperature fluctuation. A maximum akinete concentration was achieved under multiple diurnal temperature fluctuations with a magnitude of 10 °C (25 °C to 15 °C).4. A fourfold increase in light intensity (25–100 μmol m−2 s−1) resulted in an approximate 14-fold increase in akinete concentration.5. High filterable reactive phosphorus (FRP) concentrations (〉70 μg L−1) in the medium, combined with a multiple diurnal temperature fluctuation of 10 °C, supported the development of the highest akinete concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01324.x
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  • 2
    Electronic Resource
    Electronic Resource
    Stimulation of photosynthetic electron transport in a salt-tolerant plant by high chloride concentrations (1982)
    [s.l.] : Nature Publishing Group
    Nature 298 (1982), S. 483-485 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Figure 1 shows the effect of added NaCl on O2 evolution in thylakoids isolated from leaves of A. marina with ferricyanide as electron acceptor. When these thylakoids were isolated and kept in the presence of 10 mM NaCl, 5 mM MgCl2, virtually no O2 evolution was detectable without added NaCl in the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/298483a0
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  • 3
    Electronic Resource
    Electronic Resource
    Characterisation of chloroplast heat shock proteins in young leaves of C4 monocotyledons (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In vivo radiolabeling of chloroplast proteins in grain sorghum (Sorghum bicolor L. cv. Texas 610) leaves and their separation by one-dimensional electrophoresis revealed at least 6 heat shock proteins (HSPs) between 24 and 94 kDa. of which the 24 kDa protein was the most prominent. All of these chloroplast heat shock proteins were found exclusively in the stroma. The 24 kDa heat shock protein, upon closer examination using two-dimensional electrophoresis proved to be two similarly-sized heat shock polypeptides with identical molecular masses and level of radiolahel incorporation, hut slightly different in isoeiectric points, suggesting isomers. Separation of stromal heat shock proteins synthesised in two other C4 monocotyledons (Punicum miliaceum L. and Umchloa panictrides L.) revealed similar putative isomers. each of 24 kDa. Several other, previously unidentified, heat shock proteins between 22 and 38 kDa were also observed in all three species. In P. miliaceum. the most prominent HSP was the pair of 24 kDa proteins, whereas in U. panicoides. it was a group of 35 to 38 kDa HSPs that was most abundant. In vivo chlorophyll fluorescence measurements showed that no sustained impairment to photosynthetic efficiency had occurred for each species after the heat stress regime. However, when cytoplasmic protein synthesis was inhibited during the high temperature treatment, a dramatic decrease was observed in photosynthetic efficiency, suggesting a possible protective role for chloroplast heat shock proteins. It was also shown that a single chloroplast HSP complex of around 380 kDa was observed in the stroma of both 5. bicolor and P. miliaceum leaves in vivo. This was in contrast to the smaller HSP complex (200–265 kDa) observed in previous studies on chloroplast heat shock proteins in Cj species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb06663.x
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  • 4
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in vivo: The role of protein turnover in photosystem II (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Divergent theories on the mechanism behind, and the nature of, photoinhibition are discussed, especially in relation to observations made in higher plant leaves. Comparisons are made with ‘lower’ plant groups and results of in vivo and in vitro experiments are considered. Irradiance-induced mechanisms involved in the regulation of PSII function and structure are discussed in connection with turnover of the DI protein. A model is presented in which a structural change in DI protein facilitates the formation of a population of dissipative PSII centres that do not participate in linear electron transport to PSI. We suggest a sophisticated regulatory mechanism whereby this variable PSII function is controlled with respect to both incident light and biochemical demand, a control which relies on feedback from both light and dark reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb06670.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthesis and plasmamembrane permeability properties of Prochloron (1984)
    Springer
    Archives of microbiology 138 (1984), S. 247-250 
    Details
    ISSN: 1432-072X
    Keywords: Prochloron ; Photosynthesis ; Electron transport ; CO2 fixation ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic carbon fixation of freshly isolated cells of Prochloron, the symbiont of Lissoclinum patella, proceeded at high rates (80–180 μmol O2·mgChl-1·h-1) in buffered seawater and showed a typical light response, saturating at about 300 μE·m-2·s-1. However, in NaCl solutions osmotically equivalent to seawater CO2-dependent O2 evolution ceased or was severely inhibited. Hypotonic or hypertonic conditions induce degrees of swelling or shrinkage, respectively, apparently causing similar increases in the plasmamembrane's permeability to ferricyanide. Initially high, but rapidly declining, rates of electron transport were observed when the cells were suspended in distilled water. This inhibition was not caused by rupture of the cells, indicating instead diffusive loss of some essential factor(s) which normally exchange easily and rapidly between the cells and/or the host environment. Such rapid exchange may be part of the mechanism of this symbiosis and, if not adequately understood, may frustrate attempts to culture Prochloron away from its host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402130
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  • 6
    Electronic Resource
    Electronic Resource
    The chloroplast thylakoid membrane system is a molecular conveyor belt (1988)
    Springer
    Acta applicandae mathematicae 19 (1988), S. 265-276 
    Details
    ISSN: 1572-9036
    Keywords: light regulation ; photoinhibition ; photosystem II ; reaction centre ; sunflecks ; thylakoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Light drives photosynthesis, but paradoxically light is also the most variable environmental factor influencing photosynthesis both qualitatively and quantitatively. The photosynthetic apparatus of higher plants is adaptable in the extreme, as exemplified by its capacity for acclimation to very bright sunny or deeply shaded conditions. It can also respond to rapid changes in light such as sunflecks. In this paper I offer a model that i) explains the thylakoid membrane organisation into grana stacks and stroma lamellae, ii) proposes a role for rapid D1 protein turnover and LHCII phosphorylation, and iii) suggests a mechanism for photoinhibition. I argue that the photosynthetic membrane system is dynamic in three dimensions, so much so that, in the light, it is in constant motion and operates in a manner somewhat analogous to a conveyor belt. D1 protein degradation is proposed to be the motor that drives this system. Photoinhibition is suggested to be due to the arrest of D1 protein turnover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046878
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of salt stress on the growth, ion content, stomatal behaviour and photosynthetic capacity of a salt-sensitive species, Phaseolus vulgaris L. (1985)
    Springer
    Planta 164 (1985), S. 151-162 
    Details
    ISSN: 1432-2048
    Keywords: Gas exchange ; Ion relations ; Phaseolus (salt stress) ; Photosynthesis (salt stress) ; Ribulose-1,5-bisphosphate carboxylase ; Salt stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phaseolus vulgaris (cv. Hawkesbury Wonder) was grown over a range of NaCl concentrations (0–150 mM), and the effects on growth, ion relations and photosynthetic performance were examined. Dry and fresh weight decreased with increasing external NaCl concentration while the root/shoot ratio increased. The Cl- concentration of leaf tissue increased linearly with increasing external NaCl concentration, as did K+ concentration, although to a lesser degree. Increases in leaf Na+ concentration occurred only at the higher external NaCl concentrations (≧100 mM). Increases in leaf Cl- were primarily balanced by increases in K+ and Na+. X-ray microanalysis of leaf cells from salinized plants showed that Cl- concentration was high in both the cell vacuole and chloroplast-cytoplasm (250–300 mM in both compartments for the most stressed plants), indicating a lack of effective intracellular ion compartmentation in this species. Salinity had little effect on the total nitrogen and ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) content per unit leaf area. Chlorophyll per unit leaf area was reduced considerably by salt stress, however. Stomatal conductance declined substantially with salt stress such that the intercellular CO2 concentration (C i) was reduced by up to 30%. Salinization of plants was found to alter the δ13C value of leaves of Phaseolus by up to 5‰ and this change agreed quantitatively with that predicted by the theory relating carbon-isotope fractionation to the corresponding measured intercellular CO2 concentration. Salt stress also brought about a reduction in photosynthetic CO2 fixation independent of altered diffusional limitations. The initial slope of the photosynthesis versus C i response declined with salinity stress, indicating that the apparent in-vivo activity of RuBP carboxylase was decreased by up to 40% at high leaf Cl- concentrations. The quantum yield for net CO2 uptake was also reduced by salt stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396077
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  • 8
    Electronic Resource
    Electronic Resource
    Two mechanisms of recovery from photoinhibition in vivo: Reactivation of photosystem II related and unrelated to D1-protein turnover (1994)
    Springer
    Planta 194 (1994), S. 15-21 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; D1 protein ; Photoinhibition (photosynthesis) ; Photosystem II (recovery) ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recovery (at 20° C) of spinach (Spinacia oleracea L.) leaf sections from photoinhibition of photosynthesis was monitored by means of the fluorescence parameter FV/FM of intact leaf tissue and of PSII-driven electron-transport activity of isolated thylakoids. Different degrees of photoinactivation of PSII were obtained by preillumination in ambient air (at 4 or 20° C), CO2-free air or at low and high O2 levels (2 or 41 %) in N2. The kinetics of recovery exhibited two distinct phases. The first phase usually was completed within about 20-60 min and was most pronounced after preillumination in low O2. The slow phase proceeded for several hours leading to almost complete reactivation of PSII. Preincubation of the leaves with streptomycin (SM), which inhibits chloroplast-encoded protein synthesis, inhibited the slow recovery phase only, indicating the dependence of this phase on resynthesis of the reaction-centre protein, D1. The fast recovery phase remained largely unaffected by SM. Both phases were strongly but not totally dependent on irradiation of the leaf with low light. When SM was absent, net degradation of the D1 protein could neither be detected upon photoinhibitory irradiation nor during following incubation of the leaf sections in low light or darkness. In the presence of SM, net D1 degradation was seen and tended to increase with O2 concentration during photoinhibition treatment. Based on these data, we suggest that photoinactivation of PSII in vivo occurs in at least two steps. From the first step, reactivation appears possible in low light without D1 turnover (fast recovery phase). Action of oxygen then may lead to a second step, in which the D1 protein is affected and reactivation requires its removal and replacement (slow phase).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201029
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  • 9
    Electronic Resource
    Electronic Resource
    Light response of D1 turnover and photosystem II efficiency in the seagrassZostera capricorni (1996)
    Springer
    Planta 198 (1996), S. 319-323 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; D1 protein turnover ; Photoinhibition ; Xanthophyll cycle ; Zostera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biochemical and biophysical parameters, including D1-protein turnover, chlorophyll fluorescence, oxygen evolution activity and zeaxanthin formation were measured in the marine seagrassZostera capricorni (Aschers) in response to limiting (100 μmol·m−2·−1), saturating (350 μmol·m−2·s−1) or photoinhibitory (1100 μmol·m−2·s−1) irradiances. Synthesis of D1 was maximal at 350 μmol·m−2·s−1 which was also the irradiance at which the rate of photosynthetic O2 evolution was maximal. Degradation of D1 was saturated at 350 μmol·m−2·s−1. The rate of D1 synthesis at 1100 μmol·m−2·s−1 was very similar to that at 350 μmol·m−2·s−1 for the first 90 min but then declined. At limiting or saturating irradiance little change was observed in the ratio of variable to maximal fluorescence (Fv/Fm) measured after dark adaptation of the leaves, while significant photoinhibition occurred at 1100 μmol·m−2·s−1. The proportion of zeaxanthin in the total xanthophyll pool increased with increasing irradiance, indicative of the presence of a photoprotective xanthophyll cycle in this seagrass. These results are consistent with a high level of regulatory D1 turnover inZostera under non-photoinhibitory irradiance conditions, as has been found previously for terrestrial plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620046
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of carbon dioxide concentration during growth on fluorescence induction characteristics of the Green Alga Chlamydomonas reinhardii (1984)
    Springer
    Photosynthesis research 5 (1984), S. 169-176 
    Details
    ISSN: 1573-5079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carbon dioxide concentration during growth is commonly not considered to be a factor influencing the photochemical properties of plants. It was observed that fluorescence induction in Chlamydomonas reinhardii cells grown at air levels of CO2 was both qualitatively and quantitatively different from that of cells grown at 5% CO2. In the two cell types, measured at equivalent chlorophyll and irradiance levels, the fluorescence intensity and the ratio of the levels of peak fluorescence (Fp) to that of the initial fluorescence (Fo) were much lower in the air-adapted than in the 5% CO2 adapted cells. The maximum fluorescence (Fmax) in the presence of diuron was also lower for air-adapted cells. Roughly twice the light input was required for the air-adapted cells to give a fluorescence induction transient and intensity equivalent to that of the 5% CO2-adapted cells. Similar properties were observed in several other unicellular green algae and in cyanobacteria. Chlamydomonas grown under variable CO2 concentrations exhibit significant differences in photosynthetic carbon metabolism and are presumed to have altered energy requirements. The observed variation in fluorescence induction may be due to changes in the properties of the thylakoid reactions (e.g. cyclic electron flow) of Chlamydomonas cells, which may, in turn, be due to a response to the altered energy requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028529
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