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  • 1
    ISSN: 1573-5079
    Keywords: apple ; infra-red gas analysis ; leaf chamber ; photosynthesis ; transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resumen Este artículo describe un sistema portátil para medir simultaneamente transpiración e intercambio de CO2 en hojas de árboles frutales en el campo. Para medir la velocidad de fotosíntesis se colectan pequeñas muestras de gas en jeringas y se inyectan al analizador de gases de luz infra-roja. Se comparan varios métodos para analizar las muestras. Se describe la cámara de absorción de CO2 utilizada, la cual puede tambien incorporarse a un sistema abierto convencional, su pequeño volumen permite detectar cambios rápidos en el intercambio de gases cuando se producen alteraciones en el ambiente.
    Notes: Abstract A portable field system for simultaneous measurement of transpiration and CO2 exchange from leaves of fruit trees is described. CO2 concentration is measured by means of infra-red gas analysis, using small gas samples collected in syringes. Methods for analysing small gas samples are compared. The leaf chamber described can also be used in a conventional laboratory open gas-exchange system, its small volume permitting measurement of very rapid changes in gas exchange in response to experimental stimuli.
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  • 2
    ISSN: 1573-5079
    Keywords: etiochloroplasts ; Pinus ; protochlorophyllide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 77 K absorption and fluorescence spectra are measured during incubation of etiochloroplast isolated from pine cotyledons and suspended in buffers with or without various co-factors (GSH, ATP, CoA Abbreviations: PChl(ide) = protochlorophyll(ide); PChlideF657 = protochloro-phyllide-lipoprotein complex with fluorescence maximum at 657 nm; Chl(ide) = chlorophyll(ide); PEG = polyethylene glycol; DCIP = 2-6-dichlorophenol indophenol; ALA = \gd aminolevulinic acid; ATP = adenosine 5\t' triphosphate; CoA = coenzyme A; NADPH = nicotinamide-adenine dinucleotide phosphate, reduced. ) and NADPH. It is shown that, in the absence of co-factors, rapid spectral changes due to denaturation of the protein-pigment complexes occur. The spectral changes differ according to whether denaturation occurs in the light or in the dark. The rate of denaturation of the Ch1-protein complexes is significantly lowered when co-factors are added and a protective effect of NADPH on the PChlide-protein complexes was observed.
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  • 3
    ISSN: 1573-5079
    Keywords: ALA-protochlorophyllide ; chlorophyll biosynthesis ; etiochloroplast ; Pinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Etiochloroplasts isolated from dark-grown pine cotyledons fed with δ-aminolevulinic acid (ALA Abbreviations: ALA=\Gd-aminolevulinic acid; Chl(ide) = chlorophyll(ide); PChlide = protochlorophyllide; PChlideA636, PChlideA650=forms of protochlorophyllide absorbing light maximally at the wavelength indicated in nm; PChlideF635, PChlideF657=PChlide forms exhibiting a fluorescence maximum at the wavelength indicated; ALA-Pchlide=PChlide formed by an exogenous ALA treatment; NADPH = nicotineamide adeninedinucleotide phosphate. ) contain, in addition to the chlorophyll forms, two protochlorophyllide complexes which emit fluorescence around 635 nm and 657 nm respectively (ALA-PChlideF635 and PChlideF657). By a combination of light flashes and periods of darkness, it is possible to phototransform PChlideF657 and thereafter, if NADPH is added to the system, to re-form this pigment-complex from the pool of ALA-PChlideF635 during the dark periods. The process of phototransformation followed by the re-formation of PChlideF657 in the presence of NADPH can be obtained in vitro five to six times consecutively. The role of NADPH in the formation of the PChlideF657 complex is discussed.
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  • 4
    ISSN: 1573-5079
    Keywords: CO2 exchange rate ; photon flux density ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract No significant differences were found between four mathematical equations describing the response of CO2 exchange rate to photosynthetic photon flux density in seven poplar clones under laboratory conditions. Choice of an optimal equation for poplar may be based on the contemplated aims. High significant differences (at p〈0.001) were found among the clones.
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  • 5
    ISSN: 1573-5079
    Keywords: cation ; chloroplast ; PSII ; spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A correlated influence of cation concentration and excitation energy level on PS II Abbreviations: AMPD = 2-amino-2-methyl-1,3-propanediol; DCIP = 2-6 dichlorophenol indophenol; DCIPH2 = DCIP in reduced state; DCIPr = rate of DCIP-reduction; DCMU = 3-(3,4 dichlorophenyl)1-1 dimethyl-urea; Fv = variable fluorescence; Fcat = Fv in the presence of added cations; Ft = Fv without added cations; HEPES = N-2-hydroxyethylpiperazine N\t'2-sulfonic acid; PS II = photosystem II; Vcat = DCIPr in presence of added cations; Vt = DCIPr without added cations. activity is demonstrated. In low light conditions (under 60 Wm−2) Mg++ effect on DCIP reduction rate (DCIPr) saturates at rather low concentrations (2–10 mM). Higher concentrations induce a quenching of the effect, as already observed by several authors. In high light conditions (1000 Wm−2) however, Mg++ is increasingly effective on DCIPr up to concentrations of 200 mM. Na+ induced variations of DCIPr are weak in low light conditions and slightly positive for 100–600 mM in strong light; no quenching occurs. Modifications in variable fluorescence do not follow those of DCIPr in all cases, especially in high light. These results allow us to distinguish three different effects of cations on the photochemistry of PS II: one on the spill-over, another on the turnover rate of the centers and the last on the cation exchange through the thylakoid membrane.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Photosynthesis research 1 (1980), S. 143-144 
    ISSN: 1573-5079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5079
    Keywords: brown algae ; cation ; chloroplast ; PS II
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A preparation of photochemically active chloroplasts of Fucus was added to a low-salt medium with high osmolarity (HEPES AMPD buffer, 1M sorbitol). The rate of DCIP reduction (DCIPr) and the variable fluorescence (Fv) of these phaeoplasts were measured and compared with the same activities in spinach chloroplasts. A study of the influence of mono- and divalent-cations showed that salt effects on PS II activity also exist in Fucus. (i) Mg++ action on Fv is similar, although noticeably weaker in Fucus than in spinach chloroplasts. (ii) Na+ has no effect on Fv of Fucus chloroplasts, but its influence on DCIPr is more pronounced than in spinach. (iii) Mg++ influence on DCIPr is largely dependent upon excitation energy. In subsaturating light (100\2-1000 W m\t-2), Mg++ stimulation increases up to 100 mM, almost doubling the level. In very low wight conditions (3Wm\t02), however, this stimulation saturates at about 10 mM; higher concentrations are no longer effective but do not quench DCIPr noticeably, unlike the case in spinach. Therefore, cations act through similar pathways on Fucus as on spinach isolated chloroplasts but the effects on PS II centers are preponderant in Fucus whereas the modifications in non-radiative decay or pigment array size are weaker.
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  • 8
    ISSN: 1573-5079
    Keywords: erythrose-4-P ; oat ; pentose-P pathway ; phosphoglucose isomerase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoglucose isomerase was partially purified from oat leaves and shown to be strongly inhibited by erythrose-4-P. Estimated Ki values were between 0.4 and 4.0 μM. The inhibition was of the competitive type with respect to either of the substrates glucose-6-P and fructose-6-P. Several other plant phosphoglucose isomerases were found to be similarly sensitive to erythrose-4-P.
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  • 9
    ISSN: 1573-5079
    Keywords: Glycine max ; light acclimation ; stand density ; competition ; leaf area index ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-saturated photosynthetic rates at air levels of carbon dioxide were measured about weekly in upper canopy leaves of two soybean cultivars grown at stand densities of 40 and 100 plants per square meter. Early in the season, when leaf area indices differed between stand densities, plants of both cultivars grown at high stand density had photosynthetic rates which averaged 23% lower than plants at low stand density. Later in the season, when there were no differences in leaf area index between stand densities, there were no differences in photosynthetic rates in the cultivar Kent, but rate differences of about 14% persisted in the cultivar Williams. In Williams mainstem leaves emerged into full sunlight later in their development at high than at low stand density. In both cultivars the oldest fully exposed leaves were photosynthetically immature for much of the season, as higher rates could be achieved by lower leaves which were shaded in situ. The results identify shading of young developing leaves and photosynthetic immaturity of fully exposed leaves as factors limiting canopy photosynthesis in soybeans, and indicate cultivar differences in how much high stand density reduces photosynthetic capacity.
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  • 10
    ISSN: 1573-5079
    Keywords: ferricyanide ; hydrophobic chromatography ; ion-exchange chromatography ; NADP-photoreduction ; polypeptides ; PS I particle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosystem I (PS I) particles were prepared from spinach leaves by a method which includes two different types of chromatographies: an ion-exchange DEAE-Toyopearl column and a hydrophobic Butyl-Toyopearl column. Potassium ferricyanide was added to the preparation media in the early steps of preparation. The addition of ferricyanide protected iron-sulfur centers from damage due to photoinactivation during preparation and preserved some unknown polypeptides on the isolated PS I. Consequently, the PS I particles isolated by the present method showed a very high activity in the NADP-photoreduction of 388 μmol NADP reduced/mg Chl/hr.
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