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  • Articles  (91)
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  • oxidation  (47)
  • photosynthesis
  • Springer  (91)
  • National Academy of Sciences
  • 2020-2024
  • 1995-1999  (91)
  • 1997  (91)
  • 1
    Electronic Resource
    Electronic Resource
    Carbon monoxide electrooxidation on porous Pt–Ru electrodes in sulphuric acid (1997)
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1275-1282 
    Details
    ISSN: 1572-8838
    Keywords: Carbon monoxide ; Pt-Ru/C catalyst ; Tafel slopes ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract CO electrooxidation on a Pt–Ru/C catalyst was investigated in sulphuric acid electrolyte. The physico-chemical properties of the Pt–Ru/C catalyst were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of temperature, CO partial pressure and proton concentration on the electrochemical oxidation rate was investigated by steady-state galvanostatic polarization measurements. The apparent activation energy decreased from 70 to 30kJmol−1 as the overpotential increased from 0.5 to 0.9V vs NHE. The reaction order with respect to carbon monoxide increased, passing from 0.4 to 1, with the increase of the overpotential from 0.5 to 0.7V vs NHE; a reaction order close to −1 with respect to the protonic concentration was observed, irrespective of the potential. Tafel slopes of about 136mVdec−1 were determined for oxidation of CO and CO/N2 mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018492122263
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and characterization of bimodal porous carbons derived from a styrene-divinylbenzene copolymer (1997)
    Springer
    Adsorption 3 (1997), S. 67-79 
    Details
    ISSN: 1572-8757
    Keywords: porous carbons ; activation ; oxidation ; surface oxygen groups ; LTPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A styrene/divinylbenzene copolymer has been used as precursor for making porous carbons with bimodal pore size distributions (i.e., with both microporosity and mesoporosity). Pretreatment of the as-received copolymer by mild oxidation in air, significantly increased the carbon yield after carbonization. Reactivity studies of the polymer-based chars to CO2 clearly show the influences of some important factors such as carbonization temperature, heating rate, soak time on char reactivities. Bimodal porous carbons were prepared by carbonization of the preoxidized styrene/divinylbenzene copolymer in N2, followed by activation in CO2 at different temperatures to different levels of burnoff. The pore structures of the porous carbons produced have been characterized by various techniques such as gas adsorption and mercury porosimetry. The surfaces of the porous carbons produced, and a commercial carbon adsorbent, have been modified with HNO3 and H2O2 treatment at various conditions. Characterization of the surface oxygen functionality, both quantitatively and qualitatively, has been achieved using techniques such as Linear Temperature Programed Desorption (LTPD) and selective neutralization of bases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133008
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  • 3
    Electronic Resource
    Electronic Resource
    The Influence of Catalyst Composition on the Oxidation Process of Carbonado Type Synthesized Polycrystalline Diamonds (1997)
    Springer
    Advanced performance materials 4 (1997), S. 297-304 
    Details
    ISSN: 1572-8765
    Keywords: carbonado ; diamond ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of carbonado type synthesized polycrystalline diamonds produced from graphite together with catalytic Ni-Mo alloy doped with TiB2 and BNcub was investigated. It was found that the addition of these boron compounds increases the oxidation resistance of the carbonado type synthesized polycrystalline diamonds. The oxidation mechanism acting on the carbonado type synthesized polycrystalline diamonds and the role of boron compounds in increasing the resistance to the oxygen reaction are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008677105534
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of fluorination of alumina support on activity of platinum catalysts for complete oxidation of benzene (1997)
    Springer
    Catalysis letters 49 (1997), S. 155-161 
    Details
    ISSN: 1572-879X
    Keywords: fluorination ; alumina ; platinum catalysts ; oxidation ; oxidation of benzene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Platinum supported on fluorinated alumina is more active for the total oxidation of benzene than is the catalyst with the same Pt loading supported on hydrophilic unfluorinated alumina. The Pt-F/alumina catalyst contains well-dispersed small Pt particles, in contrast to Pt/alumina. The high dispersion is a consequence of a strong metal-support interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019065507551
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  • 5
    Electronic Resource
    Electronic Resource
    Short-term dynamics in protein and amino acid metabolism (1997)
    Springer
    European journal of nutrition 36 (1997), S. 336-339 
    Details
    ISSN: 1436-6215
    Keywords: Amino acids ; protein ; metabolism ; meal feeding ; oxidation ; breath test ; Aminosäuren ; Protein ; Stoffwechsel ; Fütterung ; Oxidation ; Atemtest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Die aktuellen Mengen an freien Aminosäuren im Blut reichen nur aus, um die Ganzkörper-Proteinsynthese für einige Minuten aufrecht zu erhalten. Das zeigt, daß die freien Aminosäurenkonzentrationen in der Zirkulation klein und konstant gehalten werden im Vergleich zu den Mengen der Aminosäuren, die täglich aufgenommen und über die Körperproteine umgesetzt werden. Das Verschwinden der Aminosäuren exogenen oder endogenen Ursprungs aus dem freien Aminosäuren-Pool, findet hauptsächlich durch die Proteinsynthese und den Aminosäurenabbau statt. Die Partitionierung der Nahrungs-Aminosäuren zwischen diesen beiden Prozessen im Kurzzeitbereich werden als bedeutsam für die Ökonomie der Ganzkörper-Aminosäuren angesehen. Eine Verbesserung der Aminosäurenökonomie könnte durch solche nutritiven Maßnahmen erreicht werden, welche die Clearance der Nahrungsaminosäuren durch die Proteinsynthese anstelle des Aminosäurenabbaus begünstigen. Diese nutritiven Maßnahmen sollten sich an den „Schwellenwerten“ des Abbaus der individuellen Aminosäuren orientieren.
    Notes: Summary Actual amounts of free amino acids in the blood are sufficient to support whole body protein synthesis for some minutes only. This indicates that the levels of free amino acids in the circulation are kept small and constant relative to the amounts of amino acids supplied by daily intake and turnover of body proteins. The clearance of the amino acids originating from either endogenous or exogenous sources is mainly due to protein synthesis and metabolic degradation. The partitioning of dietary amino acids between these processes, on the short term, is supposed to play an important role in whole body amino acid economy. Therefore whole body amino acid economy could be improved by nutritional measures that favour the clearance of dietary amino acids by protein synthesis instead of by metabolic degradation. These nutritional measures should to be focused on threshold values for metabolic degradation of individual amino acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01617818
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  • 6
    Electronic Resource
    Electronic Resource
    C60: A host lattice for the intercalation of oxygen? (1997)
    Springer
    Microchimica acta 125 (1997), S. 401-406 
    Details
    ISSN: 1436-5073
    Keywords: fullerenes ; intercalation ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The investigation of structural and electronic properties of the novel family of fullerenes depends on the existence of pure reference materials. Sublimation of the van-der Waals solids is a suitable purification method. Little attention has been paid to the question about the air stability of such sublimed samples in form of crystals or thin films. A combination of thermal desorption spectroscopy, thermal analysis and diffuse reflectance FT-IR spectroscopy is used to show the extent to which oxygen from dry air is intercalated into fullerenes and which detrimental reactivity occurs from attempts to thermally remove („nneal”) air-exposed samples. The conclusion is that any fullerene sample exposed to air will be transformed in part into a polymeric non-fullerene carbon upon thermal treatment to above 400 K irrespective of its initial purity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246218
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  • 7
    Electronic Resource
    Electronic Resource
    Methane oxidation in soils with different textures and land use (1997)
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 91-95 
    Details
    ISSN: 1573-0867
    Keywords: greenhouse effect ; land use ; methane ; oxidation ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Intact core samples from soils with different textures and land use were tested for their capacity to oxidise methane. The soil cores were taken from arable land, grassland and forest. It was found that coarse textured soils (6.74–16.38 µg CH4 m-2 h-1) showed a higher methane uptake rate than fine textured soils (4.66–5.34 µg CH4 m-2 h-1). Increasing soil tortuosity was thought to reduce the methane oxidation rate in fine textured soils. The oxidation rate of forest soils (16.32–16.38 µg CH4 m-2 h-1), even with a pH below 4.5, was very pronounced and higher than arable land (11.40–14.47 µg CH4 m-2 h-1) and grassland (6.74–9.30 µg CH4 m-2 h-1). Within the same textural class arable land showed a faster methane uptake rate than grassland. In grassland with a fine texture, even methane production was observed. Nitrogen availability and turnover in these land use systems were thought to cause the different oxidation rates. Decreasing the moisture content slowed down the oxidation rate in all soils. This could be caused by an increased N turnover and a starvation of the methanotrophic bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009706324386
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  • 8
    Electronic Resource
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    The effect of agriculture on methane oxidation in soil (1997)
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 59-70 
    Details
    ISSN: 1573-0867
    Keywords: land use ; methane ; nitrogen fertilizer ; oxidation ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Aerobic soils are an important sink for methane (CH4) contributing up to 15% of annual global CH4 destruction. However, the sink strength is significantly affected by land management, nitrogen (N) fertilizers and acidity. We tested these effects on samples taken from the Broadbalk Continuous Wheat, Park Grass permanent grassland and Broadbalk and Geescroft Wilderness experiments at Rothamsted. The rates of uptake from the atmosphere of both enhanced (10 ppmv) and ambient (2 ppmv) concentrations of CH4 were measured in laboratory incubations of soil cores under controlled conditions. The most rapid rates of uptake were measured in soil from deciduous woodland at pH 7 (measured in water); acidic (pH 4) woodland soil showed no net CH4 oxidation. While disturbance of the cores used in the experiments did not affect the rate of CH4 uptake, extended (150 years) cultivation of land for arable crops reduced uptake rate by 85% compared to that in the soil under calcareous woodland. The long-term application of ammonium- (NH4) based fertilizer, but not nitrate- (NO3) based fertilizer, completely inhibited CH4 uptake, but the application for the same period of farmyard manure that contained more N than the fertilizer had no inhibitory effect. Although the effects of agricultural practice on the oxidation of CH4 in soil are significant, the differences in oxidation rates between land use types are even greater. The likely effects of forest clearance, agricultural intensification and anthropogenic emissions of CH4 over the last 2500 years have been estimated for the United Kingdom. The calculations indicate that 54% of the current CH4 uptake by UK soils is the result of increased CH4 mixing ratio. They also indicate that land use change has decreased the potential sink strength by 62% or 37 kt CH4 g-1. In countries with much larger land areas than the UK, such as China, aerobic soil is likely to be a more significant factor in calculating net fluxes of CH4. It is important that the impacts of different agricultural managements and land use systems are understood and quantified so that the best possible estimate of CH4 sinks is calculated for comparison with sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009704226554
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of Interference and Oxidation on the UV/Visible Rejection Properties of Filters for Soft X-ray Detectors (1997)
    Springer
    Experimental astronomy 7 (1997), S. 51-63 
    Details
    ISSN: 1572-9508
    Keywords: X-ray ; calibration ; filters ; interference ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on UV/Visible transmission measurements of aluminum coated Lexan filters designed as UV blocking filters for soft x-ray detectors. Transmission of the filters in the 2300-8000 Å wavelength range is significantly higher than expected. It cannot be accounted for applying a simple slab model of the transmission and adopting material properties reported in the literature. We show that this is due to interference effects which are strongly dependent on the filter geometry, and to oxidation of exposed aluminum surfaces and/or chemical interaction with the plastic support. The results of this work have led to the redesign of the Advanced X-ray Astrophysics Facility High Resolution Camera UV blocking filters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007919005280
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  • 10
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    The impact of elevated CO2 on growth and photosynthesis in Agrostis canina L. ssp. monteluccii adapted to contrasting atmospheric CO2 concentrations (1997)
    Springer
    Oecologia 110 (1997), S. 169-178 
    Details
    ISSN: 1432-1939
    Keywords: Key words Agrostis canina ; CO2 vents ; photosynthesis ; lignification ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The aim of this study was to characterise growth and photosynthetic capacity in plants adapted to long-term contrasting atmospheric CO2 concentrations (C a). Seeds of Agrostis canina L. ssp. monteluccii were collected from a natural CO2 transect in central-western Italy and plants grown in controlled environment chambers at both ambient and elevated CO2 (350 and 700 μmol mol−1) in nutrient-rich soil. Seasonal mean C a at the source of the plant material ranged from 610 to 451 μmol CO2 mol−1, derived from C4 leaf stable carbon isotope discrimination (δ13C). Under chamber conditions, CO2 enrichment stimulated the growth of all populations. However, plants originating from elevated C a exhibited higher initial relative growth rates (RGRs) irrespective of chamber CO2 concentrations and a positive relationship was found between RGR and C a at the seed source. Seed weight was positively correlated with C a, but differences in seed weight were found to explain no more than 34% of the variation in RGRs at elevated CO2. Longer-term experiments (over 98 days) on two populations originating from the extremes of the transect (451 and 610 μmol CO2 mol−1) indicated that differences in growth between populations were maintained when plants were grown at both 350 and 700 μmol CO2 mol−1. Analysis of leaf material revealed an increase in the cell wall fraction (CWF) in plants grown at elevated CO2, with plants originating from high C a exhibiting constitutively lower levels but a variable response in terms of the degree of lignification. In vivo gas exchange measurements revealed no significant differences in light and CO2 saturated rates of photosynthesis and carboxylation efficiency between populations or with CO2 treatment. Moreover, SDS-PAGE/ LISA quantification of leaf ribulose bisphosphate carboxylase/oxygenase (Rubisco) showed no difference in Rubisco content between populations or CO2 treatments. These findings suggest that long-term adaptation to growth at elevated CO2 may be associated with a potential for increased growth, but this does not appear to be linked with differences in the intrinsic capacity for photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050146
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  • 11
    Electronic Resource
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    Anaerobic ammonia oxidation with nitrogen dioxide by Nitrosomonas eutropha (1997)
    Springer
    Archives of microbiology 167 (1997), S. 106-111 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsNitrosomonas ; Anaerobic ammonia ; oxidation ; Anaerobic cell growth ; Nitrogen dioxide ; Nitric oxide ; Nitrous oxide ; Dinitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (NO2) was supplemented to the atmosphere. In the presence of gaseous NO2, ammonia was oxidized, nitrite and nitric oxide (NO) were formed, and hydroxylamine occurred as an intermediate. Between 40 and 60% of the produced nitrite was denitrified to dinitrogen (N2). Nitrous oxide (N2O) was shown to be an intermediate of denitrification. Under an N2 atmosphere supplemented with 25 ppm NO2 and 300 ppm CO2, the amount of cell protein increased by 0.87 mg protein per mmol ammonia oxidized, and the cell number of N. eutropha increased by 5.8 × 109 cells per mmol ammonia oxidized. In addition, the ATP and NADH content increased by 4.3 μmol ATP (g protein)–1 and 6.3 μmol NADH (g protein)–1 and was about the same in both anaerobically and aerobically grown cells. Without NO2, the ATP content decreased by 0.7 μmol (g protein)–1, and the NADH content decreased by 1.2 μmol (g protein)–1. NO was shown to inhibit anaerobic ammonia oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050422
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  • 12
    Electronic Resource
    Electronic Resource
    Determination of kerogen type by using DSC and TG analysis (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 745-753 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; kerogen ; oxidation ; pyrolysis ; type determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e. a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC. Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined either in the case of pyrolysis or oxidation followed by DSC analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01996758
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  • 13
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    Using isothermal microcalorimetry for the prediction and testing of long-term properties of materials and products (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1017-1023 
    Details
    ISSN: 1572-8943
    Keywords: degradation ; microcalorimetry ; moisture ; oxidation ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The use of isothermal microcalorimetry (MC) as a sensitive monitor for slow reactions is demonstrated in a number of examples. In Example 1 the spontaneous decomposition of a nitrate ester propellant is studied and the absolute degradation rate estimated. Example 2 illustrates how MC can be used for comparing the rate of oxidative ageing at different O2 concentrations. Synergetic effects between oxygen and moisture in accelerated ageing of nitrile rubber are evaluated from a so-called 4-point test in Example 3. The last example shows a simple MC technique for rapid determination of moisture permeability through a polymeric sealant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01996789
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  • 14
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    Thermal properties and reactivity determination of micro- and submicrometer nickel powders (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 657-664 
    Details
    ISSN: 1572-8943
    Keywords: nickel powders ; oxidation ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Monodispersed fine metal nickel powders of uniform shape and high purity are increasingly required for specific uses in many technological areas, especially in the preparation of electronic materials such as the manufacture of conductive inks and pastes and the formation of catalysts. Metallic nickel powders were prepared in ethylene glycol by the reduction of a nickel solution. Hydrazine was used as a reducing agent. Metal powders were characterized by chemical analysis, scanning electron microscopy (SEM), thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). Particle size distributions were determined using laser light scattering. The reactivity and purity of these fine nickel powders were tested by repeated oxidation and reduction of nickel powders in oxidative and reductive atmospheres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979511
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  • 15
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    Thermogravimetric studies of the synthesis of cas from gypsum, CaSo4·2H2O and phosphogypsum (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1501-1507 
    Details
    ISSN: 1572-8943
    Keywords: calcium sulphide ; gypsum ; oxidation ; phosphogypsum ; reduction ; stability ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using a heating rate of 2°C min−1, CaS reacts with oxygen in air from 700°C to form CaSO4, with a complete conversion at 1100°C. Synthesis of CaS from the reaction between CaSO4 containing compounds and carbon compounds in air would not be possible, as the carbon reacts from 600°C with oxygen in the air to give CO2. Heating stoichiometric amounts of carbon and pure CaSO4, synthetic gypsum or phosphogypsum in a nitrogen atmosphere, results in the formation of CaS from 850°C. Using a heating rate of 10°C min−1, the formation of CaS is completed at 1080°C. Addition of 5% Fe2O3 as a catalyst lowers the starting temperature of the reaction to 750°C. Activation energy values at different fraction reaction values (α) differ between 340 and 400 kJ mol−1. The relationship between the activation energy values and conversion (α) indicates that the reaction proceeds via multiple steps.
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    URL: http://dx.doi.org/10.1007/BF01983709
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  • 16
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    Low/high temperature relationships in dinitramide salts by DEA/DSC and study of oxidation of aluminum powders by DSC/TG (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1161-1170 
    Details
    ISSN: 1572-8943
    Keywords: basicity ; dinitramides ; kinetics ; oxidation ; tanδ ; transition temperatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dinitramide salts of ammonia (ADN), hexamethylenetetramine (HDN), potassium (KDN), and sodium (NaDN) showed a linear relationship between the DSC rate of decomposition at the peak maximum and the DEA tanδ value at the low temperature transition peak. As the cation basicity increased in the series ADN〈HDN〈KDN〈NaDN, there was an increase in the low temperature transition peak, the energy barrier for relaxation, and the decomposition peak temperature, and a decrease in the tanδ value at the low temperature transition peak, specific heat capacity, and the rate and enthalpy of decomposition. The more basic salts were more thermally stable (i.e., higher decomposition temperature) and less energetic (i.e., lower enthalpy of decomposition). The more internal free volume (disorder) present in these salts, the higher the rates of relaxation and decomposition. Five aluminum powders of different surface areas were analyzed by DSC in platinum sample pans, and it was found that the enthalpy and rate of oxidation increased as the particle size of Al decreased while the enthalpy of the Al melt decreased. TG showed a two-step weight gain in the oxidation of Al with plateaus in the 650 and 1130°C regions and the percent weight gain increased as the particle size of Al decreased. Variable DSC and TG heating rate studies showed that the activation energies for the first step in the oxidation process increased as the particle size of Al increased.
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    URL: http://dx.doi.org/10.1007/BF01983671
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  • 17
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    Oxidation behavior of several chromia-forming commercial nickel-base superalloys (1997)
    Springer
    Oxidation of metals 47 (1997), S. 381-410 
    Details
    ISSN: 1573-4889
    Keywords: Ni-Base superalloys ; Astroloy ; Waspaloy ; Udimet 720 ; oxidation ; chromia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several commercially available Ni-base superalloys were exposed isothermally in air at temperatures between 750° and 1000°C and also under cyclic conditions at 1000°C. The kinetics of oxidation were determined and the scales were analyzed by electron microscopy and X-ray diffraction. Thin adherent chromia-rich scales formed on the alloys at 750°C after 1000 hr. Although Waspaloy showed the lowest weight gain in this test, it also showed the deepest internal corrosion due to oxidation of the grain-boundary carbides. At temperatures up to 1000°C the external scales were also chromia-rich but there was greater internal corrosion. Titanium in the alloys oxidized, diffusing through the chromia scale to form faceted rutile (TiO2) grains at the surface as well as forming TiO2 and TiN internally. The amount of rutile at the oxide surface increased with temperature and alloy Ti concentration. Alumina formed as discrete internal oxides below the chromia scale, although Astroloy when oxidized isothermally at 1000°C developed a semicontinuous internal layer of alumina due to its higher Al content. Under cyclic conditions Astroloy formed a thicker, less-protective scale of transition oxides probably due to its lower Cr content.
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    URL: http://dx.doi.org/10.1007/BF02134783
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  • 18
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    Oxidation behavior of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy at high temperature in Ar-H2O atmospheres (1997)
    Springer
    Oxidation of metals 47 (1997), S. 411-426 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; Incoloy 909 ; superalloy ; scale ; high temperature ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy (Incoloy 909 type alloy), was investigated at temperatures between 1000 K and 1400 K in Ar-(1, 10%)H20 atmosphere using metallographic, electron probe microanalysis, and X-ray diffraction techniques. The oxide scales consist of an external scale and an internal scale which has an intergranular scale (above 1200 K) and an intergranular scale. The oxide phases in each scale are identified asα-Fe2,O3 (below 1200 K) or FeO (above 1300 K) and CoO · Fe2O3 and FeO · Nb2O5, respectively. The morphologies, the oxide phases and the oxidation rates do not depend on the partial pressure of H2O in the range between one and ten percent in Ar gas. The rate constants for the intergranular-scale formation in this alloy are about one-tenth as large as those in Fe-36%Ni alloy reported previously. At all the temperatures the scales grow according to a parabolic rate law and the apparent activation energies for the processes are estimated.
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    URL: http://dx.doi.org/10.1007/BF02134784
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  • 19
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    Water-vapor-effect on the oxidation of Fe-21.5 wt.%Cr-5.6 wt.%Al at 1000°C (1997)
    Springer
    Oxidation of metals 47 (1997), S. 445-464 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-Cr-Al alloy ; water vapor ; ESCA ; RHEED
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fe-21.5 wt. %Cr-5.6 wt. %Al oxidation, at 1000°C, in dry or wet oxygen shows that steam has an influence on the oxide-scale growth mechanism. Steam modifies the kinetics of early-stage oxidation. In dry oxygen, an initial fast linear regime is observed during one hour. Under wet conditions, weight-gain curves follow the same parabolic regime over the entire oxidation test. The scale structure strongly depends on the presence of steam in the gaseous environment. With dry oxygen, the scale is composed mainly ofα-Al2O3 after the initial formation ofγ-Al2O3 identified by ESCA and RHEED. The kinetics transient stage corresponds to the necessary time for the internal part of the initialγ-Al2O3 scale to transform into a continuousα-Al2O3 diffusion barrier. Under wet oxygen conditions, transient oxides are identified as (Mg, Fe) (Cr, Al)2O4, MgAl2O4 (orthorhombic), Al2O3 (hexagonal), these oxides transform into MgAl2O4 (cubic), Cr3O4, Fe2O3,α-Al2O3, with time. When water vapor does not change drastically oxidation kinetics, the induced presence of iron and chromium in the oxide scale could be responsible for weakening the protectiveness of alumina scales.
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    URL: http://dx.doi.org/10.1007/BF02134786
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    The transient state in the oxidation of binary alloys forming the most-stable oxide: A numerical solution (1997)
    Springer
    Oxidation of metals 47 (1997), S. 507-524 
    Details
    ISSN: 1573-4889
    Keywords: alloys ; high temperature ; oxidation ; transient state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The initial transient high-temperature oxidation stage for binary alloys forming the most-stable oxide has been examined by means of a numerical procedure based on the finite-difference method. At variance with previous models, the present treatment takes into account the effect of the rate of the reaction at the scale/gas interface over the corrosion kinetics. The calculations concerning the transient stage are developed either using the general parabolic rate law to represent the overall scaling kinetics or using the rate law of the reaction at the scale/gas interface as a boundary condition without imposing any particular rate law to the overall process. A correct analysis of the oxidation behavior of binary alloys during the transient stage must take into account the kinetics effect of the rate of the surface reaction. The concentration of the most-reactive element at the alloy/scale interface changes regularly with time, decreasing gradually from the initial bulk value to its final steady-state value. The present results are in good agreement with those obtained by means of an approximate analytical model developed previously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02134789
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    An approximate treatment of the transient state in the oxidation of binary alloys forming the most-stable oxide. Part II: Single-phase alloys in systems with a solubility gap (1997)
    Springer
    Oxidation of metals 47 (1997), S. 525-550 
    Details
    ISSN: 1573-4889
    Keywords: high temperatures ; oxidation ; transient state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The transient state in the oxidation of solid solutions of a most-noble componentA in a most-reactive componentB (beta phase) for binaryA-B alloys presenting a limited reciprocal solubility of the two metals has been examined assuming that theirB content is sufficient for the exclusive growth of externalBO scales. Above a criticalB content of the alloy theBO scales may grow directly on the surface of the beta phase, while below this limit they can only form over a layer ofB-depleted solid solution ofB inA (alpha phase), which appears after a critical time. An approximate analytical expression for the profile of concentration ofB in the alloy has been adopted to calculate the flux ofB in the metal. Moreover, the effect of the reaction between the gas and the external oxide surface has been taken into account using a procedure developed by Wagner for the oxidation of pure metals. The corrosion kinetics as well as all the parameters involved, such as the concentration ofB at the alloy-scale interface, have been calculated as functions of the corrosion time. The results show that, as time proceeds, the instantaneous parabolic rate constant increases and the concentration ofB at the alloy-scale interface decreases, both tending gradually to their corresponding steady-state values. It is also predicted that if the rate of transformation of the beta phase in the alpha phase after the alloy reaches the composition of equilibrium at the interface with the oxide is lower than the corresponding rate of displacement of the alloy surface due to scale growth, the corrosion of beta phase alloys may eventually lead to the formation of two phase mixtures of alpha phase andBO which are expected to grow at much larger rates than in the presence of a uniform continuous alpha layer.
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    URL: http://dx.doi.org/10.1007/BF02134790
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    Evolution of oxides on Ni-base ODS superalloys (1997)
    Springer
    Oxidation of metals 48 (1997), S. 1-39 
    Details
    ISSN: 1573-4889
    Keywords: Ni-base ODS superalloys ; oxidation ; initial stages of oxidation ; alumina ; chromia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Mechanically-alloyed Ni-base ODS superalloys currently receive attention for application in future gas turbines because they exhibit outstanding mechanical properties at high temperatures. They also protect themselves against oxidation by forming chromia and/or alumina scales. However, little attention has been given so far to the initial stages of oxidation of Ni-base ODS superalloys, containing Cr as well as Al in considerable amounts. In the current work, oxidation at 1150°C was studied for different holding times up to 200 hr for the commercial materials MA6000 and PM3030 which contain. Al in increasing amounts. MA 754, a chromia former, was investigated as a reference. It was shown that for the potential alumina formers MA6000 and PM3030 the continuity and therefore protectiveness of the secondary Al2O3 at later stages is indeed determined by the initial stages of oxidation.
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    URL: http://dx.doi.org/10.1007/BF01675260
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    Decarburization and internal oxidation in a commercial-grade nickel (1997)
    Springer
    Oxidation of metals 48 (1997), S. 129-141 
    Details
    ISSN: 1573-4889
    Keywords: decarburization ; nickel ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A commercial-grade nickel containing small amounts of carbon, manganese, and silicon was exposed to air for periods up to 288 hr at 1050°C to study the effect of oxidation on the formation of oxides of these impurity elements. Exposure of nickel to air led to decarburization. The maximum amount of decarburization occurred during the initial period of air exposure and the loss in carbon was more in the metal with a smaller section size. Decarburization in the metal produced voids in the oxide scale due to the formation of CO2 gas. It has been shown further that CO and/or CO2 gas bubbles, which form in high purity nickel on grain boundaries during exposure to air at elevated temperatures, cannot exist in commercial-grade nickel where manganese is present as an impurity. Instead, oxides of manganese form in the grain boundaries as well as in the matrix. This is because manganese oxide is more stable than CO or CO2 gas.
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    URL: http://dx.doi.org/10.1007/BF01675265
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    On the oxidation ofα-Fe andε-Fe2N1−z : I. Oxidation kinetics and microstructural evolution of the oxide and nitride layers (1997)
    Springer
    Oxidation of metals 48 (1997), S. 87-109 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; kinetics ; iron ; iron-nitride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of α-Fe and ɛ-Fe2N1−z at 573 K and 673 K in O2 at 1 atm was investigated by thermogravimetrical analysis, X-ray diffraction, light-optical microscopy, scanning electron microscopy and electron probe X-ray microanalysis. Upon oxidation at 573 K and 673 K, on α-Fe initially α-Fe2O3 develops, whereas on ɛ-Fe2N1−z initially Fe3O4 develops. In an early stage of oxidation the oxidation rate of ɛ-Fe2N1−z appears to be much larger than of α-Fe. This can be attributed largely to an effective surface area available for oxygen uptake, which is much larger for ɛ-Fe2N1−z than for α-Fe due to the porous structure of ɛ-Fe2N1−z as prepared by gaseous nitriding of iron. The development of a magnetite layer in-between the hematite layer and the α-Fe substrate, at a later stage of oxidation, enhances layer-growth kinetics. After 100 min oxidation at 673 K the (parabolic) oxidation rates for α-Fe and ɛ-Fe2N1−z become about equal, indicating that on both substrates the oxide growth is controlled by the same rate limiting step which is attributed to short-circuit diffusion of iron cations. Oxidizing ɛ-Fe2N1−z increases the nitrogen concentration in the remaining ɛ-iron nitride, because the outward flux of iron cations, necessary for oxide growth, leads to an accumulation of nitrogen atoms left behind.
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    URL: http://dx.doi.org/10.1007/BF01675263
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    Effect of niobium additions on CO2-enhanced oxidation of titanium-aluminum intermetallic alloys (1997)
    Springer
    Oxidation of metals 48 (1997), S. 201-214 
    Details
    ISSN: 1573-4889
    Keywords: titanium-aluminum alloys ; niobium ; intermetallics ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In a recent study, CO2 has been reported to enhance the oxidation rate of binary titanium-aluminum alloys. The detrimental effect of CO2 was not, however, observed in a ternary alloy containing niobium. In this paper, possible explanations for these observations are examined. First, results from the literature regarding the effects of niobium in improving the resistance of titanium-aluminum alloys are briefly reviewed. Second, a thermodynamic analysis which offers a possible explanation for the beneficial effect of niobium in eliminating the CO2-enhanced oxidation of titanium-aluminum alloys is presented.
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    URL: http://dx.doi.org/10.1007/BF01670499
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    The effect of nanocrystallization on the selective oxidation and adhesion of Al2O3 scales (1997)
    Springer
    Oxidation of metals 48 (1997), S. 215-224 
    Details
    ISSN: 1573-4889
    Keywords: nanocrystallization ; oxidation ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Many mechanisms for the effect of reactive elements on the selective oxidation and scale adhesion of alloys have been proposed. However, nanocrystallization (or microcrystallization) has recently been found to have almost the same effect as that of reactive elements. This note reviews the effect of nanocrystallization on the selective oxidation and adhesion of Al2O3 scale with particular reference to the author's own results.
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    URL: http://dx.doi.org/10.1007/BF01670500
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    High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres (1997)
    Springer
    Oxidation of metals 48 (1997), S. 289-302 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; titanium ; rutile ; scale ; high temperature ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO2 or Ar-10%CO2. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO2) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.
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    URL: http://dx.doi.org/10.1007/BF01670504
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    Phase analysis by variable-incidence X-ray diffraction: Application to zirconium oxidation (1997)
    Springer
    Oxidation of metals 48 (1997), S. 329-345 
    Details
    ISSN: 1573-4889
    Keywords: zirconium ; X-ray diffraction ; oxidation ; phase analysis ; texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of zirconium at high temperature (T〉 400°C) leads to reaction products of two allotropic oxide (ZrO2 monoclinic and ZrO2 tetragonal). The distribution and proportion of these two phases were studied as a function of time and space by X-ray diffraction techniques. Quantitative analyses are possible after some corrections, and we demonstrate the presence of a phase gradient in the oxide scale. The interest of this nondestructive method is then discussed.
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    URL: http://dx.doi.org/10.1007/BF01670506
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    The air oxidation of two-phase Cu-Cr alloys at 700–900°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 357-380 
    Details
    ISSN: 1573-4889
    Keywords: chromium ; copper ; binary alloys ; two-phase alloys ; oxidation ; high temperatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation in air of three two phase Cu-Cr alloys with nominal Cr contents of 25, 50, and 75 wt. % was studied at 700–900°C. The alloys corroded nearly parabolically, except at 900°C, when the corrosion rates decreased with time more rapidly than predicted by the parabolic rate law. The corrosion rate decreased for higher Cr contents in the alloy under constant temperature and generally increased with temperature for the same alloy composition. The scales were complex and consisted in most cases of an outermost copper oxide layer free from chromium and an inner layer composed of a matrix of copper oxide or of the double oxide Cu2Cr2O4, often containing particles of chromium metal surrounded by chromia and then by the double oxide. Metallic copper was also frequently mixed with chromia. Cr-rich regions tended to form continuous chromia layers at the base of the scale, especially at the highest temperature. No chromium depletion was observed in the alloy.
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    URL: http://dx.doi.org/10.1007/BF02153456
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    Influence of ceria coatings on growth stresses developed in wüstite scales formed on pure iron at 800°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 417-438 
    Details
    ISSN: 1573-4889
    Keywords: iron ; oxidation ; CeO2 coating ; in situ ; growth stress ; residual stress ; texture ; X ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In situ XRD stress determinations have been performed during oxidation of pure iron (p(O2=2 × 10−3 Pa,T=800°C)). The compressive stress, initially present in the substrate due to surface preparation, is completely released at 400°C. Under the test conditions, the in situ compressive-stress level determined in the FeO scale during oxidation is not strongly dependent upon the presence of a ceria coating. On blank and coated specimens, the compressive stress varies from −400 ± 80 MPa to −150 ± 100 MPa during 30 hr oxidation. The decrease is quicker at the beginning of the test performed on blank specimens. Epitaxial relationships between the wüstite scale and iron (under low-pressure starting conditions) caused thein situ compressive stress in the oxide scale to be two times greater compared to the usual test conditions. This indicates that epitaxial relationships can be a source of stress in an oxide scale that ceria coatings may lower compressive stresses.
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    URL: http://dx.doi.org/10.1007/BF02153459
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    Chloridation-oxidation of Fe-Cr and Ni-Cr alloys at 800°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 527-551 
    Details
    ISSN: 1573-4889
    Keywords: chloridation ; oxidation ; Fe-Cr alloys ; Ni-Cr alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The chloridation-oxidation behavior of Fe-Cr (0–25 wt. %Cr) and Ni-Cr (0–20 wt.%Cr) alloys was studied at 800°C in three different H2-HCl-H2O(ν) environments. In a low-HCI and low-H2O(ν) environment, where Cr2O3 is thermodynamically stable, the corrosion resistance of the Fe-Cr alloys increased with increasing Cr content in the alloys. In a high-HCl and high-H2O(ν) environment, where FeCr2O4 is stable and CrCl2 is metastable, the corrosion resistance of the Fe-Cr alloys depended similarly on the Cr content. Low-Cr-Fe-Cr alloys exhibited large weight losses, while Fe-Cr alloys with higher than 19 wt. %Cr showed good corrosion resistance. In an environment of high-HCl in the absence of H2O(ν), the evaporative corrosion rate was fast and limited by gas phase diffusion, and independent of the Cr content in the Fe-Cr alloys. Ni and Ni-Cr alloys generally showed good corrosion resistance in the environments of high H2O(ν) because of the low NiCl2 vapor pressure and formation of a protective Cr2O3 scale. However, in the environment of high HCl in the absence of H2O(ν), selective formation and evaporation of CrCl2 occur, which results in Cr depletion and networks of voids for even a high-Cr Ni-Cr alloy.
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    Chloridation-oxidation of nine commercial high-temperature alloys at 800°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 553-596 
    Details
    ISSN: 1573-4889
    Keywords: chloridation ; oxidation ; HCl ; high-temperature alloys ; high-temperature corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Chloridation-oxidation studies of nine commercial high-temperature alloys were carried out at 800°C in three different H2-HCl-H2O(ν) environments: (A) both low HCl and H2O(ν) partial pressures, where either Cr2O3 or FeCr2O4 is stable, (B) both high HCl and H2O(ν) partial pressures, where FeCrO4 is stable and CrCl2 is metastable, and (C) high HCl partial pressure in the absence of H2O(ν), where either CrCl2 or Cr2O3 is stable. Although alloy 600 has the lowest Cr content of these nine alloys, it showed excellent corrosion resistance in all three environments because of its high Ni content. Alloy 304, with the lowest Ni content of the nine alloys, exhibited poor corrosion resistance in the environment C, fair resistance in the environment B and good resistance in the environment A. Alloy 800 showed very good resistance in Environment A, and fair corrosion resistance in Environment B; however, it suffered linear weight-loss kinetics when exposed to Environment C The alloys 617, 214, HR-160, X, 230 and 86 have good corrosion resistance in Environments A and B because of their relatively high contents of oxide-scale-forming elements Cr and/or Al. In Environment C, chlorine dramatically decreased the adhesion of the scale on the surface, and aluminum in alloys 617 and 214 hardly showed its usual beneficial effect in combating corrosion, nor does silicon in alloy HR-160. Different corrosion mechanisms are proposed for the alloys in the different environments.
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    An approximate treatment of the transient state in the corrosion of binary alloys forming the most-stable oxide. Part I: Solid-solution alloys (1997)
    Springer
    Oxidation of metals 47 (1997), S. 91-115 
    Details
    ISSN: 1573-4889
    Keywords: binary alloys ; oxidation ; transient state ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The initial transient stage in the oxidation of binary alloys forming scales exclusively composed of the most stable oxide is examined by means of a simplified approach which avoids the numerical integration of the diffusion equation for the transport of the metal components in the alloy. At variance with previous solutions to this problem obtained by means of numerical methods, this treatment takes into account also the effect of the gas-scale reaction at the outer surface of the oxide. The concentration of the most-reactive component at the alloy surface changes gradually with time from the initial bulk value towards the corresponding steady-state value without involving any minimum, while the overall rate of the reaction presents a gradual transition from an initial nearly linear towards final parabolic behavior.
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    URL: http://dx.doi.org/10.1007/BF01682373
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    Oxidation resistance of sputtered Ni3(AlCr) nanocrystalline coating (1997)
    Springer
    Oxidation of metals 47 (1997), S. 247-258 
    Details
    ISSN: 1573-4889
    Keywords: Ni3Al-base alloy ; sputtering ; nanocrystalline coating ; oxidation ; scale adhesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Isothermal and cyclic oxidation resistance at 1000°C in air were investigated for a cast Cr-containing Ni3Al-base alloy and its sputtered nanocrystalline coating. The results indicated that both the cast Ni3Al alloy and its sputtered coating exhibit excellent isothermal oxidation resistance as a result of the formation of Al2O3 scales. However, the cast alloy possesses very poor cyclic oxidation resistance because of the spallation of the initially formed Al2O3 scale during cooling and subsequent formation of NiO. On the contrary, the sputtered Ni3(AlCr) nanocrystalline coating exhibits very good cyclic oxidation resistance due to the significant improvement of the adhesion of Al2O3.
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    Prevention of lens protein glycation by taurine (1997)
    Springer
    Molecular and cellular biochemistry 177 (1997), S. 245-250 
    Details
    ISSN: 1573-4919
    Keywords: cataract ; crystalline ; glycation ; oxidation ; taurine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Modifications in lens protein structure and function due to nonenzymic glycosylation and oxidation have been suggested to play a significant role in the pathogenesis of sugar and senile cataracts. The glycation reaction involves an initial Schiff base formation between the protein NH2 groups and the carbonyl group of a reducing sugar. The Schiff base then undergoes several structural modifications, via some oxidative reactions involving oxygen free radicals. Hence certain endogenous tissue components that may inhibit the formation of protein-sugar adduct formation may have a sparing effect against the cataractogenic effects of sugars and reactive oxygen. The eye lens is endowed with significant concentration of taurine, a sulfonated amino acid, and its precursor hypotaurine. It is hypothesized that taurine and hypotaurine may have this purported function of protecting the lens proteins against glycation and subsequent denaturation, in addition to their other functions. The results presented herein suggest that these compounds are indeed capable of protecting glycation competitively by forming Schiff bases with sugar carbonyls, and thereby preventing the glycation of lens proteins per se. In addition, they appear to prevent oxidative damage by scavenging hydroxyl radicals. This was apparent by their preventive effect against the formation of the thiobarbituric acid reactive material generated from deoxy-ribose, when the later was exposed to hydroxyl radicals generated by the action of xanthine oxidase on hypoxanthine in presence of iron.
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    URL: http://dx.doi.org/10.1023/A:1006863322454
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    Sol-Gel Coatings on Metals (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 443-449 
    Details
    ISSN: 1573-4846
    Keywords: coatings ; protection of metals ; oxidation ; corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel derived films can be deposited on metals to improve their resistance to oxidation and corrosion or to modify their surface properties. However, practical applications are limited by problems intrinsic to sol-gel processing or specific of coating/metal systems. Coatings aimed to improve oxidation and wet corrosion resistance have been the most studied. The results published in the literature show that sol-gel coatings may offer good protection against oxidation. More difficult is to achieve a protection against wet corrosion. An important aspect of the application of the sol-gel method for coating metallic objects is also the deposition technique.
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    URL: http://dx.doi.org/10.1023/A:1018373404815
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    Sol-gel coatings on metals (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 443-449 
    Details
    ISSN: 1573-4846
    Keywords: coatings ; protection of metals ; oxidation ; corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel derived films can be deposited on metals to improve their resistance to oxidation and corrosion or to modify their surface properties. However, practical applications are limited by problems intrinsic to sol-gel processing or specific of coating/metal systems. Coatings aimed to improve oxidation and wet corrosion resistance have been the most studied. The results published in the literature show that sol-gel coatings may offer good protection against oxidation. More difficult is to achieve a protection against wet corrosion. An important aspect of the application of the sol-gel method for coating metallic objects is also the deposition technique.
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    URL: http://dx.doi.org/10.1007/BF02436880
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    The air oxidation of two-phase Cu-Ag alloys at 650–750°C (1997)
    Springer
    Oxidation of metals 47 (1997), S. 21-52 
    Details
    ISSN: 1573-4889
    Keywords: copper ; silver ; high temperature ; oxidation ; two-phase alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The corrosion of three two phase Cu-Ag alloys containing 25, 50, and 75 wt% Ag has been studied at 650 and 750°C. In all cases the alloys formed external scales of copper oxides. At the same time, an internal precipitation of Cu2O within a silver matrix was also produced, with an oxide volume fraction larger for the alloys richer in Cu. Beneath this mixed layer a region of single-phase solid solution of Cu in silver formed for Cu-50Ag and especially for Cu-75Ag. Silver metal remained in the metal-consumption zone, acting essentially as an inert marker, except for a few particles with were incorporated into the growing scales. Both pure Cu and the alloys corroded parabolically, but the rate constants for the alloys decreased with increased Ag content under constant temperature. The various aspects of the corrosion of these alloys are examined by taking into account the possible effects associated with the presence of two metal phases.
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    Identification of diffusing species and the dynamic nature of diffusion paths during oxidation of a dilute Ni-Cr alloy (1997)
    Springer
    Oxidation of metals 47 (1997), S. 69-89 
    Details
    ISSN: 1573-4889
    Keywords: duplex-layer formation ; dynamic oxygen-diffusion path ; Ni-Cr alloy ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The results of an investigation of oxidation of a Ni-1 at.% Cr alloy are presented. Photolithographic marker experiments revealed that the markers were found to reside at the interface between a predominantly columnar outer NiO layer and a very fine grain inner layer of NiO, indicating that substantial oxygen ingress had occurred through the columnar scale. New oxide growth at the metal-oxide interface requires the oxidant to be transported across the oxide layer. Since the measured diffusion rate of oxygen ions along grain boundaries and through the lattice is much too slow to account for the observed microstructural growth (∼1: 1 ratio of inner and outer layers), it is necessary to postulate that the oxidant traverses the scale along some type of short-circuit path other than grain boundaries. Extensive formation of elongated pores and pipelike channels was observed along columnar oxide grain boundaries. Thus, it appears that the transport of oxygen occurs via voids (pores) formed by vacancy coalescence at the columnar grain boundaries. These pores appear to open and close continuously. Formation of new fine-grained oxide in these pores was observed to have sometimes completely resealed the void, suggesting a dynamic nature of the voids.
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    URL: http://dx.doi.org/10.1007/BF01682372
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    Oxidation of the intermetallics MoSi2 and TiSi2—A comparison (1997)
    Springer
    Oxidation of metals 47 (1997), S. 139-203 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; MoSi2 ; TiSi2 ; air ; oxygen ; O and Si transport in SiO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of two MoSi2 variants, one Mo-rich and one Si-rich, and TiSi2 was investigated between 1000 and 1400°C in air, oxygen and an 80/20-Ar/O2 mixture. A protective SiO2 scale develops on MoSi2 in all atmospheres in the temperature range investigated. The SiO2 modification changes around 1300°C from tridymite to cristobalite. This change in SiO2 modification seems to cause an enhanced formation of SiO2 and evaporation of MoO3. The SiO2 grows at the MoSi2-scale interface. In air a two-layer scale grows on TiSi2 between about 1000 and 1200°C with an inner inwards growing fine-grain mixture of SiO2 + TiO2 and an outer outward-growing TiO2 partial layer. TiN formation in the transient oxidation is responsible for the formation of the inner mixed partial layer because in N -free atmospheres a scale of a SiO2 matrix with some Ti oxide precipitates inside is formed. A one-layer scale structure similar as that in N-free atmosphere is found on TiSi2 in air at T 〉 1200°C. In oxygen the TiO2 precipitates grow as needles mostly oriented perpendicular to the surface. Due to the faster oxygen transport in TiO2 compared with SiO2, these TiO2 needles act as “oxygen pipes,” causing an enhanced oxidation of TiSi2 in front of these needles. The SiO2 scale dissolves about 1–2% TiO2. This doping causes a mixed oxygenand Si transport with the consequence that the SiO2 scale on TiSi2 grows partly by oxygen transport inwards and Si transport outwards. The SiO2 modification is cristobalite over the entire temperature range investigated.
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    URL: http://dx.doi.org/10.1007/BF01682375
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    The steady-state corrosion kinetics of single-phase binary alloys with a solubility gap forming the most-stable oxide (1997)
    Springer
    Oxidation of metals 47 (1997), S. 215-235 
    Details
    ISSN: 1573-4889
    Keywords: high temperature ; oxidation ; binary alloys ; steady-state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The steady-state, high-temperature oxidation kinetics of single phase alloys rich in a most-reactive componentB in binaryA-B systems presenting a limited solubility of the two components (beta phase alloys) have been examined assuming the exclusive formation of the most-stable oxideBO v. Alloys sufficiently rich inB can form externalBO v scales directly in contact with the beta phase, while below a criticalB content the growth ofBO v involves also the appearance of an intermediate layer ofB-depleted solid solution ofB inA (alpha phase). The parabolic rate constants for the oxidation of single-phase beta alloys are lower than those of alloys of identicalB content which are single-phase over the whole range of composition (solid-solution alloys) but higher than for two-phase alpha + beta alloys under the same values of all the relevant parameters. Moreover, the tendency of single-phase beta alloys to form the most-stable oxide simultaneously as an external scale and internally to the alloy is greater than for solid-solution alloys but smaller than for two-phase alloys.
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    URL: http://dx.doi.org/10.1007/BF01668511
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    High-temperature oxidation behavior of laser-surface-alloyed incoloy-800H with Al (1997)
    Springer
    Oxidation of metals 47 (1997), S. 259-275 
    Details
    ISSN: 1573-4889
    Keywords: laser surface alloying ; aluminum ; superalloys ; oxidation ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The high-temperature oxidation resistance of laser-surface-alloyed Incoloy 800H with Al has been investigated. Several samples have been exposed to 1000°C in air and subsequently analyzed by optical microscopy, SEM, and electron microprobe X-ray fluorescence spectroscopy in order to determine their microstructure and composition. The results show that the laser-treated materials have a considerably higher oxidation resistance than the nontreated materials due to the formation of an Al-rich layer close to the surface, which acts as a barrier against oxygen diffusion into the bulk.
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    URL: http://dx.doi.org/10.1007/BF01668514
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    Site-directed mutagenesis of the basic residues 321K to321 G in the CP 47 protein of photosystem II alters the chloride requirement for growth and oxygen-evolving activity in Synechocystis 6803 (1997)
    Springer
    Plant molecular biology 34 (1997), S. 455-463 
    Details
    ISSN: 1573-5028
    Keywords: photosystem II ; photosynthesis ; chlorophyll-binding protein ; Synechocystis ; oxygen evolution ; oligonucleotide-mediated mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract CP 47, a component of photosystem II (PSII) in higher plants, algae and cyanobacteria, is encoded by the psbB gene. Site-specific mutagenesis has been used to alter a portion of the psbB gene encoding the large extrinsic loop E of CP 47 in the cyanobacterium Synechocystis 6803. Alteration of a lysine residue occurring at position 321 to glycine produced a strain with altered PSII activity. This strain grew at wild-type rates in complete BG-11 media (480 µM chloride). However, oxygen evolution rates for this mutant in complete media were only 60% of the observed wild-type rates. Quantum yield measurements at low light intensities indicated that the mutant had 66% of the fully functional PSII centers contained in the control strain. The mutant proved to be extremely sensitive to photoinactivation at high light intensities, exhibiting a 3-fold increase in the rate of photoinactivation. When this mutant was grown in media depleted of chloride (30 µM chloride), it lost the ability to grow photoautotrophically while the control strain exhibited a normal rate of growth. The effect of chloride depletion on the growth rate of the mutant was reversed by the addition of 480 µM bromide to the chloride-depleted BG-11 media. In the presence of glucose, the mutant and control strains grew at comparable rates in either chloride-containing or chloride-depleted media. Oxygen evolution rates for the mutant were further depressed (28% of control rates) under chloride-limiting conditions. Addition of bromide restored these rates to those observed under chloride-sufficient conditions. Measurements of the variable fluorescence yield indicated that the mutant assembled fewer functional centers in the absence of chloride. These results indicate that the mutation K321G in CP 47 affects PSII stability and/or assembly under conditions where chloride is limiting.
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    URL: http://dx.doi.org/10.1023/A:1005826411702
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    Yield, water use efficiency and nitrogen uptake in potato: influence of drought stress (1997)
    Springer
    Potato research 40 (1997), S. 19-34 
    Details
    ISSN: 1871-4528
    Keywords: water stress ; photosynthesis ; stress index ; dry matter partitioning ; tuber quality ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A lysimeter experiment was performed to study the optimal allocation of limited water supply in potatoes. Irrigation regimes equal to 40, 60 and 80% of maximum evapotranspiration (ET) were evenly applied over the crop cycle. Other treatments involved withholding 80 mm of irrigation, based on ET, beginning at each of three designated growth stages (tuber initiation, early and late tuber growth). An irrigated control treatment, restoring the entire ET, was included for comparison. Continuous drought stress reduced photosynthesis as irrigation volumes were reduced. Plant biomass and tuber yield decreased almost proportionally to water consumption, so that WUE was roughly constant. N uptake was highest in the control and in 80% ET treatment. Withholding water during tuberisation severely hindered plant physiological processes and penalized tuber yield. Reductions in photosynthesis, total biomass and yield were the greatest when drought was imposed during tuber initiation. The earliest stress resulted in the lowest WUE and N uptake. A new crop water stress index (SI) was proposed, which combines atmospheric demand for water and canopy temperature.
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    URL: http://dx.doi.org/10.1007/BF02407559
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    Influence of tidal location on morphology, photosynthesis and pigments of the agarophyte, Gelidiella acerosa, from Northern Philippines (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 525-532 
    Details
    ISSN: 1573-5176
    Keywords: Gelidiella ; agarophyte ; photosynthesis ; P-I curve ; morphology ; tide ; pigment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The red seaweed agarophyte, Gelidiella acerosa (Forsskål) (Feldmann& Hamel) was collected from tidepools, high intertidal rocks. and shallow subtidal are as along a reef flat in Ilocos Norte, northern Philippines. The three populations were compared during the summer (dry) and rainy (wet) seasons to determine changes in morphology and photoacclimation capacity as possible use in mariculture. During summer months (February toApril) after exposure to environmental extremes (i.e. the highest percent of minus tides during daylight, high light regimes, desiccation, and solar bleaching), the populations differed in their morphologies and responses to increasing irradiance levels (P–I curve). Tidepool plants were the tallest, bushiest, and with increased diameter of cortical cells; while,high intertidal plants were the shortest, with sparse branching pattern and decreased diameter of cortical cells. Although their saturation irradiances indicated shade tolerance (Ik = 52 − 112 µmol photon m -2 s-1). their differential light saturation curves (P-I curves) suggested a capacity to acclimate to ambient light regimes. For example, plants from the high intertidal zone showed higher photosynthetic rates and saturation irradiances, slightly lower initial slopes of the P-I curves and levels of light harvesting accessory pigments, rphycoerhythrin (R-PE) and rphycocyanin (R-PC), after being exposed to higher light regimes. In contrast, plants from tidepools and shallow subtidal areas had lower photosynthetic rates and saturation irradiances, slightly steeper initial slopes of the P-I curves and levels of R-PE and R-PC, having been exposed to lower light regimes. During the rainy months (June to November) no significant responses in these parameters were recorded. Comparison of the P-I responses of vegetative and tetrasporic plants showed these to vary with season. The data suggest that when plants became reproductive their physiological fitness either was unchanged or slightly enhanced. These results indicate that all three populations of G. acerosa could be used as seed stock for mariculture.
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    URL: http://dx.doi.org/10.1023/A:1007968201873
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    Improvement of photosynthesis in dense microalgal suspension by reduction of light harvesting pigments (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 503-510 
    Details
    ISSN: 1573-5176
    Keywords: Chlorella pyrenoidosa ; dense algalsuspension ; light-harvesting pigment ; photosynthesis ; Synechocystis PCC 6714
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of light-harvesting pigments (LHP) inmicroalgal cells on photosynthetic activity in adense cell suspension were examined. The results suggest that a lower LHP content should result in higher photosynthetic productivity under high light intensity. The idea was first proposed by Lien and San Pietro in 1975 that photosynthesis could be improved by reducing the LHP content in microalgal cells, but this has not been demonstrated in detail. Experiments to evaluate the idea were conducted with Synechocystis PCC6714 and Chlorellapyrenoidosa. In the experiments with PCC 6714, photosynthesis of a phycocyanin-deficient mutant was compared with that of the wild type. In the experiments with C. pyrenoidosa, the LHP content was controlled by the light intensity in the algalculture. The maximum photosynthetic activity was 20–30% higher in the dense suspension of cells having a lower LHP content with both organisms. These results indicate that the idea of reducing the LHP contentcould be applicable to a wide variety of photosynthetic organisms.
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    URL: http://dx.doi.org/10.1023/A:1007920025419
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    The interactive effects of UV-B radiation and a herbicide on uptake and allocation of carbon in two strains of the green algaScenedesmus (1997)
    Springer
    Aquatic ecology 31 (1997), S. 261-272 
    Details
    ISSN: 1573-5125
    Keywords: sherbicide tolerance ; photosynthesis ; phytoplankton ; simetryn ; triazine ; herbicides ; ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the effects of UV B radiation on14C-uptake rates and carbon assimilation into the major end-products of photosynthesis of the green algaScenedesmus in the presence and absence of the triazine herbicide simetryn. Experiments were conducted using both a herbicide-susceptible and herbicide-tolerant strains ofScenedesmus. Three different UV-B dose rates were used as well as a light control. The lowest dose rate was almost the same level as in subsurface of ponds and lakes, while the other two were slightly lower and higher than natural sunlight on the surface of ponds and lakes, respectively. Total uptake rates of14C were not reduced by the UV B irradiation alone even at the highest dose rate. However, in the presence of the herbicide, uptake rates were clearly reduced by the highest dose rate of UV-B concomitant with increasing herbicide concentrations in the herbicide-susceptible strain. On the other hand, the proportion of lipid fraction was slightly reduced by all the UV-B treatments in the herbicide-susceptible strain even in the absence of the herbicide. In the herbicide-tolerant strain, uptake rates were not affected by UV-B radiation or by the herbicide. These facts indicated that UV-B effects could be smaller than predicted. It may be important to examine combined effects of UV-B and other anthropogenic and/or natural stresses for assessing actual UV-B effects in the field.
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    URL: http://dx.doi.org/10.1007/BF02493513
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    Seasonal and spatial patterns in phytoplankton photosynthetic parameters in a tidal freshwater river (1997)
    Springer
    Hydrobiologia 364 (1997), S. 199-208 
    Details
    ISSN: 1573-5117
    Keywords: Phytoplankton ; photosynthesis ; light ; temperature ; tidal freshwater ; irradiance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic response to irradiance wasquantified for phytoplankton from the tidalfreshwater Potomac River biweekly to monthly over aperiod of six years. Samples were collected from twoshallow embayments and portions of the deeper rivermainstem. Photosynthetic rate was measured in thelaboratory at in situ temperature over a range ofirradiance levels and photosynthetic parameters werecalculated using nonlinear regression.PB max,the maximum photosynthetic ratestandardized to chlorophyll a, increased withtemperature up to 25 °C with a Q10 of 2.02. Above 25 °C, PB max was essentiallyconstant with temperature. Lesser correlationbetween PB max and ambient irradiance couldbe explained by the correlation of irradiance withtemperature. α, the slope of the P–I curve atlow light, was correlated with both ambientirradiance and temperature. Highest α valueswere found in late summer when high temperature andintermediate ambient irradiance were observed. Spring and early summer were characterized by lowα. Despite low light penetration, Ik andα values were indicative of sun limitationpossibly due to intermittent high light levelsexperienced during mixing. Ik showed a clearseasonal trend directly related to days from summersolstice. Spatial patterns were minimal except thatIk was consistently lower in one shallowembayment than in the other two areas. Seasonalpatterns in photosynthetic parameters correspondedroughly to changes from a spring diatom populationto summer cyanobacterial assemblage.
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    URL: http://dx.doi.org/10.1023/A:1003107306421
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    Gas exchange responses of a mangrove species, Avicennia marina, to waterlogged and drained conditions (1997)
    Springer
    Hydrobiologia 352 (1997), S. 39-47 
    Details
    ISSN: 1573-5117
    Keywords: Avicennia marina ; gas exchange ; mangroves ; photosynthesis ; waterlogging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was undertaken in summer on fully expanded leaves of Avicennia marina trees in the Beachwood Mangroves Nature Reserve, Durban,South Africa. Data sets were obtained over 5–7 days of relatively dry conditions and over two periods of 5 days during which the swamp was continuously inundated with dilute seawater (〈 150 mol m−3NaCl). Gas exchange responses were strongly influenced by photosynthetic photon flux density (PPFD), leaf temperature and leaf to air vapour pressure deficit (Δw). Carbon dioxide exchange was saturated at a PPFD of about 800 µmol m−2 s−1. Maximal CO2 exchange rates ranged from 8.5 to 9.9 µmol m−2 s−1 with no differences between drained and waterlogged conditions. Under drained conditions, leaf conductance,transpiration and internal CO2 concentrations were generally lower, and water use efficiencies higher, than during waterlogging. Continuous waterlogging for 5 days had no adverse effect on CO2 exchange. Xylem water potentials ranged from −1.32to −3.53 MPa during drained and from −1.02 to −2.65 Mpa during waterlogged conditions. These results are discussed in relation to anatomical and metabolic adaptations of A. marina to waterlogging stress.
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    Lumenal proteins involved in respiratory electron transport in the cyanobacterium Synechocystis sp. PCC6803 (1997)
    Springer
    Plant molecular biology 35 (1997), S. 407-416 
    Details
    ISSN: 1573-5028
    Keywords: cyanobacteria ; cytochrome oxidase ; electron transport ; photosynthesis ; respiration ; thylakoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyanobacterial thylakoids catalyze both photosynthetic and respiratory activities. In a photosystem I-less Synechocystis sp. PCC 6803 strain, electrons generated by photosystem II appear to be utilized by cytochrome oxidase. To identify the lumenal electron carriers (plastocyanin and/or cytochromes c 553, c 550, and possibly c M) that are involved in transfer of photosystem II-generated electrons to the terminal oxidase, deletion constructs for genes coding for these components were introduced into a photosystem I-less Synechocystis sp. PCC 6803 strain, and electron flow out of photosystem II was monitored in resulting strains through chlorophyll fluorescence yields. Loss of cytochrome c 553 or plastocyanin, but not of cytochrome c 550, decreased the rate of electron flow out of photosystem II. Surprisingly, cytochrome c M could not be deleted in a photosystem I-less background strain, and also a double-deletion mutant lacking both plastocyanin and cytochromec 553 could not be obtained. Cytochrome c M has some homology with the cytochrome c-binding regions of the cytochromecaa3 -type cytochrome oxidase from Bacillus spp. and Thermus thermophilus. We suggest that cytochrome c M is a component of cytochrome oxidase in cyanobacteria that serves as redox intermediate between soluble electron carriers and the cytochromeaa3 complex, and that either plastocyanin or cytochrome c 553 can shuttle electrons from the cytochrome b6f complex to cytochrome c M.
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    An Uncoupling of the Processes of Oxidation and Phosphorylation in Glycolysis (1997)
    Springer
    Bioscience reports 17 (1997), S. 521-527 
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    ISSN: 1573-4935
    Keywords: Glyceraldehyde-3-phosphate dehydrogenase ; glycolysis ; oxidation ; uncoupling ; thiols ; hydrogen peroxide ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Data on alterations of the properties of glyceraldehyde-3-phosphate dehydrogenase upon oxidation of its functional groups are reviewed; a mechanism of uncoupling of oxidation and phosphorylation in glycolysis is considered. Possible ways of regulating uncoupling, and the physiological importance of this process, are discussed.
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    Can stomatal closure caused by xylem ABA explain the inhibition of leaf photosynthesis under soil drying? (1997)
    Springer
    Photosynthesis research 51 (1997), S. 149-159 
    Details
    ISSN: 1573-5079
    Keywords: abscisic acid ; t Acacia confusa ; t Leucaenaleucocephala ; photosynthesis ; soil drying ; stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of leaf water deficit and increase in endogenous ABA on photosynthesis of two tropical trees, t Acacia confusa and t Leucaena leucocephala, were investigated with two soil-drying methods, i.e. half or whole root system was subjected to soil drying. Half-root drying was achieved by allowing upper layer of soil column to dry and lower layer of soil column to remain watered. Half-root drying had little effect on leaf water potential, but when compared to the well-watered control, both methods of soil drying substantially increased the ABA concentration in xylem and reduced leaf conductance in both species. There was a significant relationship between leaf conductance and xylem ABA concentrations in both species, which was comparable to the same relationship that was generated by feeding ABA to excised twigs. The rate of photosynthesis was inhibited substantially in both soil-drying treatments and in both species, but photochchemical efficiency, measured as a ratio of variable fluorescence to a peak fluorescence emission of a dark-adapted leaf (Fv/Fm), was not reduced except in the whole root-dried t L. leucocephala plants where leaf water potential was reduced to –2.5 MPa. In all the cases where photosynthesis was inhibited, there was a concomitant reduction in both leaf conductance and calculated internal CO2 concentration. After two days of rewatering, leaf water potential and xylem ABA concentration rapidly returned to pre-treatment levels, but leaf conductance and photosynthesis of both whole-root and half root dried t L. leucocephala remained inhibited substantially. Rewatering led to a full recovery of both stomatal conductance and photosynthesis in soil-dried t A. confusa, although its photosynthesis of whole-root dried plants did not recover fully but such difference was not significant statistically. These results suggest that drought-induced decline of photosynthesis was mainly a result of the stomatal factor caused by the increase of ABA concentration in the xylem sap. Non-stomatal factors, e.g. reduced photochemical activity and/or carbon metabolic activity, were species-specific and were brought about only at very low water potential.
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    Regulation of photosynthesis in developing leaves of soybean chlorophyll-deficient mutants (1997)
    Springer
    Photosynthesis research 51 (1997), S. 185-192 
    Details
    ISSN: 1573-5079
    Keywords: CAB ; cytochrome f ; photosynthesis ; Rubisco ; Rubisco activase ; senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this report we examine the factors that regulate photosynthesis during leaf ontogeny in y3y3 and Y11y11, two chlorophyll-deficient mutants of soybean. Photosynthetic rates were similar during wild type and Y11y11 leaf development, but the senescence decline in photosynthesis was accelerated in y3y3. Photosynthetic rates fell more rapidly than chlorophyll concentrations during senescence in wild type leaves, indicating that light harvesting is not strongly limiting for photosynthesis during this phase of leaf development. Chlorophyll concentrations in Y11y11, though significantly lower than normal, were able to support normal photosynthetic rates throughout leaf ontogeny. Chlorophyll a/b ratios were constant during leaf development in the wild type, but in the mutants they progressively increased (y3y3) or decreased (Y11y11). In all three sets of plants, photosynthetic rates were directly proportional to Rubisco contents and activities, suggesting that Rubisco plays a dominant role in regulating photosynthesis throughout leaf ontogeny in these plants. The expression of some photosynthetic proteins, such as Rubisco activase, was coordinately regulated with that of Rubisco in all three genotypes, i.e. an early increase, coincident with leaf expansion, followed by a senescence decline in the fully-expanded leaf. On the other hand, the light harvesting chlorophyll a/b-binding proteins of PS II (the CAB proteins), while they showed a profile similar to that of Rubisco in the wild type and y3y3, progressively increased in amount during Y11y11 leaf development. We conclude that Y11y11 may be defective in the accumulation of a component required for LHC II assembly or function, while y3y3 has more global effects and may be a regulatory factor that controls the duration of senescence.
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    Biomass accumulation and allocation in soybean associated with genotypic differences in tolerance of nitrogen fixation to water deficits (1997)
    Springer
    Plant and soil 196 (1997), S. 101-113 
    Details
    ISSN: 1573-5036
    Keywords: drought ; Glycine max ; photosynthesis ; water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen fixation in soybean (Glycine max [L.] Merr.) is more sensitive to water deficits than many physiological processes and may therefore limit yield under nonirrigated conditions. Tolerance of nitrogen fixation to water deficits has been observed in the cultivar Jackson, however, the physiological basis for this is unclear. It was hypothesized that genotypes that could continue biomass production on limited soil water would prolong nitrogen fixation by continued photosynthate allocation to nodules. An initial greenhouse experiment compared biomass and N accumulation in six genotypes over an 8 d water deficit. Low stress intensity minimized genotypic expression of water-deficit tolerance; nevertheless, Jackson was clearly one of the most tolerant genotypes. In a second experiment, Jackson was compared to SCE82-303 at more severe stress levels. Biomass and N accumulation continued during water deficits for Jackson but ceased in SCE82-303. Individual nodule mass tended to increase during water deficits in Jackson and tended to decrease in SCE82-303, indicating greater allocation of photosynthate to Jackson's nodules in response to water deficits. Biomass accumulation of Jackson was contrasted with the USDA plant introduction (PI) 416937, which also has demonstrated tolerance to water deficits. For water-deficit treatments, total biomass accumulation was negligible for PI416937, but biomass accumulation continued at approximately 64% of the control treatment for Jackson. Transpirational losses for Jackson and PI416937 were approximately the same for the water-deficit treatment, indicating that Jackson had higher water use efficiency (WUE). Isotopic discrimination of 13C relative to12 C also indicated that Jackson had superior WUE during water deficits. Carbon-14 allocation in Jackson was compared to KS4895, a cultivar that was identified as sensitive to water deficits in an initial experiment. The comparison of water-deficit treatments of Jackson with KS4895 indicated that Jackson exported significantly greater amounts of14 C from labeled leaves and allocated approximately four times greater amounts of 14C per g of nodule. Results indicated that Jackson's sustained biomass production during water deficits resulted in the continued allocation of photosynthate to nodules and prolonged nitrogenase activity.
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    Does boron play only a structural role in the growing tissues of higher plants? (1997)
    Springer
    Plant and soil 196 (1997), S. 211-215 
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    ISSN: 1573-5036
    Keywords: boron ; deficiency ; function ; membrane ; mobility ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In species in which boron (B) mobility is limited, B deficiency only occurs in growing plant organs. As a consequence of the highly localized patterns of plant growth and the general immobility of B it has been extremely difficult to determine the primary function of B in plants. In species in which B is phloem mobile, the removal of B from the growth medium results in the depletion of B present in mature leaves. Thus, it is possible to develop mature leaves with increasingly severe levels of B depletion, thereby overcoming the complications of experiments based on growing tissues. Utilizing this approach we demonstrate here that B depletion of mature plum (Prunus salicina) leaves did not result in any discernible change in leaf appearance, membrane integrity or photosynthetic capacity even though B concentrations were reduced to 6-8 µg/g dwt, which is less than 30% of the reported tissue B requirement. Boron depletion, however, results in a severe disruption of plant growth and metabolism in young growing tissues. This experimental evidence and theoretical considerations suggest that the primary and possibly sole function of B, is as a structural component of growing tissues.
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    Effect of genome and ploidy on photosynthesis of wheat (1997)
    Springer
    Euphytica 94 (1997), S. 303-309 
    Details
    ISSN: 1573-5060
    Keywords: photosynthesis ; hexaploid wheat ; A genome ; D genome ; polyploidy ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We assessed (1) the effects of addition and doses of the D genome from different sources and (2) the addition of either the A genome or the D genome on the photosynthesis of synthesized hexaploid wheats. On average, the increased doses of the D genome reduced photosynthesis, but the depression was dependent on the source of the D genome. Two accessions of Aegilops squarrosa had depressed photosynthetic rates, but not another accession of Ae. squarrosa. The D genome of cv. Thatcher did not contribute to depress photosynthetic rate. Triticum monococcum had considerably higher photosynthetic rates than Ae. squarrosa. However, addition of the A genome from T. monococcum did not increase the photosynthetic rates of hexaploids. Chlorophyll a : b ratio, functional photosystem II and the core complex of photosystem II did not account for the variation in photosynthetic rate among the genotypes studied. In our experiment, photosynthesis of polyploids was not dependent on photosynthesis rates of the donor genomes.
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    Oceanic picophytoplankton having a high abundance of chlorophyll b in the major light harvesting chlorophyll protein complex (1997)
    Springer
    Photosynthesis research 53 (1997), S. 121-127 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll a/b light-harvesting complex ; major LHCP ; oceanic picophytoplankton ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chl a-containing, very small unicellular, eukaryotic phytoplankton (picophytoplankton) often become the dominant organisms near the bottom of the euphotic zone in the ocean, where light is limited, not only in intensity (about 0.5% of the surface irradiance), but also in quality (dominant in blue to green wavelengths). We have isolated picophytoplankton from subsurface waters (from 75 to 150 m in depth) of the Kuroshio area near Japan. EM observations showed that a single chloroplast occupies a large part of the cytoplasm. Some of the isolates have a flagellum. The major photosynthetic pigments found in these isolates were chlorophyll a and b. The light-harvesting chlorophyll a/b complex (LHCP) was isolated from three clones of picophytoplankton, one flagellated form (NIBB8001) and two coccoid forms (94B8100A and 94B5100C) . More than 50% of the total chlorophylls were recovered in the major LHCP fraction. A common feature of the major LHCPs isolated from the three picophytoplankton clones was a high abundance of chlorophyll b: the ratios of chlorophyll a to b were about 0.8, 0.7 and 0.6 for the clones NIBB8001, 94B8100A and 94B5100C, respectively. These values were very low compared with those in chlorophyll a/b-binding LHCIIs in higher plants and in the major chlorophyll a/b-binding LHCPs in microalgae (higher than 1.0). The major LHCP apoproteins of NIBB8001 and 94B5100C contained one major polypeptide; the apparent molecular masses analyzed with SDS-PAGE were about 22 kDa and 27 kDa, respectively. The major LHCP apoprotein of 94B8100A had two major polypeptides having apparent molecular masses of about 23 and 25 kDa. None of the thylakoid proteins cross-reacted with an antibody raised against the LHC IIα apoprotein of spinach. It is suggested that the high abundance of chlorophyll b in picophytoplankton, together with a large chloroplast in a small cell, enable them to utilize the reduced light in their habitat.
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    Chromophore assignment in phycoerythrocyanin from Mastigocladus laminosus (1997)
    Springer
    Photosynthesis research 54 (1997), S. 25-34 
    Details
    ISSN: 1573-5079
    Keywords: cyanobacteria ; energy transfer ; Fischerella PCC 7603 ; photosynthesis ; phycobiliprotein ; phycoerythrocyanin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The component spectra (maxima of absorption, circular and linear dichroism) of individual chromophores have been assigned for phycoerythrocyanin (PEC) trimer, monomer(s), and its subunits (α-PEC and β-PEC) by titration with p-chloromercury-benzene-sulfonate (PCMS), linear dichroism and photochemical transformations, as well as by deconvolution using a ‘bilin’ line-shape spectrum based on the α-84 phycoviolobilin-chromophore in the α-subunit. The level ordering PVB-α-84 → PCB-β-155 → PCB-β-84 is the same irrespective of aggregation. Two different monomers (αβ) were observed. In 4 M urea, the spectra are appropriately weighted sums of the subunit spectra, whereas in the monomer obtained in 1 M KSCN, both β-chromophores are red-shifted by 4–5 nm. Formation of trimer (αβ)_3gives considerable spectral changes: (1) the absorption is narrowed, which has been rationalized by excitonic coupling between neighbouring monomers, (2) the short wavelength part in the CD spectrum is missing and (3) a fourth band (+) at 528 in the LD spectrum appears. A deconvolution of the trimeric aggregation state using only the ‘bilin’ line-shape model is not possible.
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    Characterisation of cytochrome c6from Chlorella fusca (1997)
    Springer
    Photosynthesis research 54 (1997), S. 107-114 
    Details
    ISSN: 1573-5079
    Keywords: CD ; Chlorella ; cytochrome c6 ; EPR ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A c-type monohaem, cytochrome c6was isolated from a soluble extract of the green alga Chlorella fusca. The isolated protein shows an apparent molecular mass of 10 kDa by SDS-PAGE, but behaves as a dimer of 20.3 kDa in gel-filtration; the isoelectric point is 3.6. The N-terminal sequence shows high identity with other green algae cytochromes c6. The mid-point redox potential is about +350 mV between pH 5 and 9. The ferric and ferrous forms, and their pH equilibria, have been studied using visible, CD and EPR spectroscopies. The visible spectrum of the reduced cytochrome c6is typical of a c-type haem protein, with maxima at 274 nm, 318 nm (δ-peak), 416 nm (γ-peak), 522 nm (β-peak), 552–553 nm (α-peak). A 690 nm band, characteristic of a haem Met-His axial coordination of the haem group, is present in the oxidized form. At high pH values (≥ 8), cytochrome c6undergoes an alkaline transition, with a pKa of 8.7. Between pH 3 and 9 the EPR spectrum is dominated by two rhombic species, with g-values at 3.32, 2.05, 1.05 and 2.96, 2.30, 1.43, which interconvert with a pKaof 4. CD spectrum of Chlorella fusca cytochrome c6shows that the proteins must be mainly built up by α-helices. Even though there are similarities between Chlorella fusca cytochrome c6and that isolated from Monoraphidium braunii, no cross-reactivity with the antibodies raised against the Chlorella fusca cytochrome has been detected for the protein from Monoraphidium braunii.
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    URL: http://dx.doi.org/10.1023/A:1005955201482
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    The effects of elevated light on Photosystem II function: A thermoluminescence study (1997)
    Springer
    Photosynthesis research 54 (1997), S. 169-183 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence quenching ; photoinhibition ; photoprotection ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used the technique of thermoluminescence (TL) to investigate high-light-induced chlorophyll fluorescence quenching phenomena in barley leaves, and have shown it to be a powerful tool in such investigations. TL measurements were taken from wild-type and chlorina f2 barley leaves which had been dark-adapted or exposed to 20 min illumination of varying irradiance or given varying periods of recovery following strong irradiance. We have found strong evidence that there is a sustained trans-thylakoid ΔpH in leaves following illumination, and that this ΔpH gives rise to quenching of chlorophyll fluorescence which has previously been identified as a slowly-relaxing component of antenna-related protective energy dissipation; we have identified a state of the PS II reaction centre resulting from high light treatments which is apparently able to perform normal charge separation and electron transport but which is ‘non-photochemically’ quenched, in that the application of a light pulse of high irradiance cannot cause the formation of a high fluorescent state; and we have provided evidence that a transient state of the PS II reaction centre is formed during recovery from such high light treatments, in which electron transport from QAto QBis apparently impaired.
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    The modification of phytosterol profiles and in vitro photosynthetic electron transport of Galium aparine L. (cleavers) treated with the fungicide, epoxiconazole (1997)
    Springer
    Plant growth regulation 22 (1997), S. 93-100 
    Details
    ISSN: 1573-5087
    Keywords: epoxiconazole ; Galium aparine L. ; photosynthesis ; phytosterols ; thylakoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Foliar application of the triazole fungicide, epoxiconazole, retarded the growth of Galium aparine L. (cleavers). GC-MS and GC analysis clearly indicated that phytosterol biosynthesis in stem and leaflet tissue was significantly affected by this treatment. For example, in leaflet tissues, 125 g ai ha-1 (field rate) caused reductions in campesterol and sitosterol of 81percnt; and 75percnt; respectively. C14-methyl phytosterols such as 14agr;-methylergost-8-enol, obtusifoliol and dihydroobtusifoliol were detected in treated tissues indicating that epoxiconazole inhibits the cytochrome P-450 dependent obtusifoliol 14agr;-demethylase. In addition, ratios of campesterol to sitosterol were reduced. Stigmasterol was not detected in control or treated tissues. Preliminary determination of photosynthetic characteristics of isolated thylakoids from treated plants indicated that electron transport and oxygen evolution were impaired by epoxiconazole and these effects were dose-related. Ten days after treatment, oxygen evolution from thylakoids (determined as electron flow from water to ferricyanide) isolated from control plants was 24.2 micro;mol mg-1 chl h-1, whilst treatment with 125 g and 250 g ai ha-1 reduced this rate to 15.2 micro;mol and 8.2 micro;mol mg-1 chl h-1 an inhibition of 37 and 67percnt; respectively. These results suggest that epoxiconazole influences thylakoid integrity and function in addition to phytosterol biosynthesis in G. aparine.
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    The dependance of root growth potential on light level, photosynthetic rate, and root starch content in jack pine seedlings (1997)
    Springer
    New forests 13 (1997), S. 105-119 
    Details
    ISSN: 1573-5095
    Keywords: field performance potential ; photosynthesis ; Pinus banksiana ; root initiation ; root starch ; seedling testing ; total nonstructural carbohydrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Number of new roots (root growth potential or RGP), new root length, photosynthesis, total nonstructural carbohydrate content of needles and roots, terminal bud condition, and shoot elongation were measured on jack pine container seedlings for 4 weeks at weekly intervals under greenhouse conditions of 100%, 20%, and 10% sunlight to simulate competition-induced, lower light levels in the field. Both lower light levels significantly reduced photosynthetic rate, RGP, new root length, total nonstructural carbohydrate (especially starch) content of needles and roots, speed of terminal bud flush, and shoot growth. Both light level and photosynthetic rate were positively correlated with RGP and new root length, indicating that jack pine seedlings may use current photosynthate as an energy source to support new root growth. RGP and new root length were also both negatively correlated with root starch content suggesting that jack pine seedlings may also use stored carbohydrates as a potential carbon source for root initiation and initial root growth.
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    URL: http://dx.doi.org/10.1023/A:1006517820981
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    The mechanism of the degradation of psaB gene product, one of the photosynthetic reaction center subunits of Photosystem I, upon photoinhibition (1997)
    Springer
    Photosynthesis research 53 (1997), S. 55-63 
    Details
    ISSN: 1573-5079
    Keywords: hydroxyl radical ; light stress ; photosynthesis ; serine protease ; protein turnover ; reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The psaB gene product (PsaB protein), one of the reaction center subunits of Photosystem I (PS I), was specifically degraded by light illumination of spinach thylakoid membranes. The degradation of the protein yielded N-terminal fragments of molecular mass 51 kDa and 45 kDa. The formation of the 51 kDa fragment was i) partially suppressed by the addition of phenylmethylsulfonyl fluoride or 3,4-dichloroisocoumarin, which are inhibitors of serine proteases, and ii) enhanced in the presence of hydrogen peroxide during photoinhibitory treatment, but iii) not detected following hydrogen peroxide treatment in the dark. These results suggest that the hydroxyl radical produced at the reduced iron-sulfur centers in PS I triggers the conformational change of the PS I complex, which allows access of a serine-type protease to PsaB. This results in the formation of the 51 kDa N-terminal fragment, presumably by cleavage on the loop exposed to the stromal side, between putative helices 8 and 9. On the other hand, the formation of the 45 kDa fragment, which was enhanced in the presence of methyl viologen but did not accompany the photoinhibition of PS I, was not affected by the addition of hydrogen peroxide or protease inhibitors. Another fragment of 18 kDa was identified as a C-terminal counterpart of the 45 kDa fragment. N-terminal sequence analysis of the 18 kDa fragment revealed that the cleavage occurred between Ala500 and Val501 on the loop exposed to the lumenal side, between putative helices 7 and 8 of the PsaB protein.
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    Characteristics of photosynthetic carbon metabolism of spikelets in rice (1997)
    Springer
    Photosynthesis research 52 (1997), S. 75-82 
    Details
    ISSN: 1573-5079
    Keywords: lemma ; light-enhanced dark CO2 fixation ; palea ; panicle ; photosynthesis ; pyruvate ; Pi dikinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In lemmas and paleae of rice, the amount of pyruvate, Pi dikinase (PPDK) protein increased dramatically 6 d after anthesis and this change was consistent with that in the activity of PPDK. Since lemmas and paleae at this stage also showed high activities of the other marker enzymes of C4 pathway including phosphot enolpyruvate carboxylase (Imaizumi et al. (1990) Plant Cell Physiol 31: 835–843), photosynthetic carbon metabolism with lemmas at this stage were characterized. In a 14C pulse-12C chase study by photosynthetic CO2 fixation, about 35% and 25% of 14C fixed in lemmas were incorporated initially into 3-phosphoglycerate (3-PGA) and C4 acids, respectively. This suggests that lemmas participate mainly in C3-type photosynthetic metabolism, but that lemmas may also participate in the metabolism of C4 acids to some extent. To clarify this possibility, large amounts of 14C-labeled C4 acids were synthesized in vivo by a light-enhanced dark CO2 fixation (LED) method and the fate of 14C in C4 acids in the light was investigated. The percentage distribution of 14C in C-4 position of malate was about 90% and 83% after 10 s of photosynthetic 14CO2 fixation and 110 s of LED, respectively. Some of the 14C incorporated into C4 acids was transferred into 3-PGA and sugar phosphates. The possibility of direct fixation of CO2 by phosphot enolpyruvate carboxylase and metabolic pathway of CO2 released by decarboxylation of malate produced were discussed.
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    Growth at high CO2 affects the chloroplast number but not the photosynthetic efficiency of photoautotrophicMarchantia polymorpha culture cells (1997)
    Springer
    Plant cell, tissue and organ culture 48 (1997), S. 103-110 
    Details
    ISSN: 1573-5044
    Keywords: bryophytes ; cell culture ; chlorophyll content ; LHC II ; photosynthesis ; Rubisco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoautotrophic suspension cells of Marchantia polymorpha were grown at gas phase CO2 concentrations of 0.4% and 2.0%. At the higher CO2 concentration the chloroplast shape appeared to be modified and the cells had about 70% more chloroplasts per cell. Differences in chlorophyll content per cell were much less pronounced, indicating a reduction in chlorophyll content per chloroplast. Also the cell size was affected by the CO2 concentration, and our data suggest that it was about 37% lower in high CO2 grown cells than in low CO2 grown cells. The capacity and the efficiency of photosynthetic oxygen evolution on a chlorophyll basis and the photosystem II chlorophyll fluorescence parameters were almost identical in both cell types. Immunodection showed that also the ratio of light harvesting complex II antenna proteins and ribulose 1,5 bisphosphate carboxylase/oxygenase were unaltered. These data indicate that the chloroplast density within photoautotrophic culture cells may be regulated independently of their photosynthetic efficiency.
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    Developmental changes in carboxylase activities in in vitro cultured coconut zygotic embryos: comparison with corresponding activities in seedlings (1997)
    Springer
    Plant cell, tissue and organ culture 49 (1997), S. 227-231 
    Details
    ISSN: 1573-5044
    Keywords: carbon metabolism ; CO2 fixation ; embryo culture ; PEPC ; photosynthesis ; RubisCO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoenolpyruvate Carboxylase (PEPC; EC: 4.1.1.31) and Ribulose 1,5-bisphosphate Carboxylase/Oxygenase (RubisCO; EC: 4.1.1.39) enzyme specific activities were measured during the in vitro development of coconut (Cocos nucifera L.) zygotic mature embryos into plantlets and compared with those of palms produced by conventional seed germination. At the time of initiation of germination, high PEPC and low RubisCO activities were measured in both cultured and conventionally germinated embryos, thus indicating an anaplerotic CO2 fixation. During both in vitro and in planta development, RubisCO progressively took over and became the main route for inorganic carbon fixation. The in vitro-grown coconut plantlets showed a faster decrease in their PEPC:RubisCO ratio than the seedlings, suggesting that an earlier transition from a heterotrophic to an autotrophic mode of carbon fixation takes place in the in vitro-derived material. Just before acclimatization, the RubisCO activity in in vitro-derived plantlets (2.83 µmol CO2h−1mg−1 TSP) was lower than that in seedlings (6.98 µmol CO2h−1mg−1 TSP) of the same age. Nevertheless, after acclimatization, RubisCO activities were comparable in both in vitro and in planta germinated material
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    The effect of different closure types, light, and sucrose concentrations on carbon isotope composition and growth ofGardenia jasminoides plantlets during micropropagation and subsequent acclimationex vitro (1997)
    Springer
    Plant cell, tissue and organ culture 47 (1997), S. 217-230 
    Details
    ISSN: 1573-5044
    Keywords: photoautotrophy ; photosynthesis ; shoot multiplication ; root induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth ofGardenia jasminoides Ellis plantlets and the development of photoautotrophy during two successive culture stages (shoot multiplication and root induction)in vitro was analyzed. We examined the effects of changes in growth conditions (type of tube closure, light, and sugar levels) on the development of photoautotrophy and growth during micropropagation and sought to establish whether they affected later acclimation to conditionsex vitro. During the two stagesin vitro, plantlets were grown in tubes under two different PPFD (50 and 110 µmol m−2 s−1), in media with three different sucrose concentrations (0, 1.5, and 3.0%, w/v) and with two different CO2 levels inside the tubes (controlled by either tightly closed caps or loosely sealed caps, and with an external CO2 concentration of 750 µmol mol−1). The development of photoautotrophy was assessed by determining the difference between the stable carbon isotope composition (δ13C) of sugar cane sucrose used as a heterotrophic carbon source and that of leaflets grownin vitro. Plantlets from the root-induction stage showed a more highly developed photoautotrophy than those from the shoot- multiplication stage. At both stages, utilization of closed caps was the treatment which most stimulated development of photoautotrophy in plantlets. Also, lowering PPFD or sucrose concentration induced a greater degree of photoautotrophic development, the strongest effect being observed in plantlets cultured inside loosely sealed tubes. During acclimationex vitro, plantlets taken from loosely sealed tubesin vitro performed better than those cultured inside tightly sealed tubes. The former, as well as recording a larger increase in fresh weight during this stage, also showed more negative δ13C in the newly developed leaves, which would seem to indicate a better water status during acclimation. Present results validate the usefulness of δ13C analysis of leaflets as a simple technique in assessing the development of photoautotrophy during culturein vitro. In addition, δ13C analysis can be extended to evaluate growth conditions during acclimation toex vitro conditions.
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    Activation and deactivation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in three marine microalgae (1997)
    Springer
    Photosynthesis research 51 (1997), S. 93-106 
    Details
    ISSN: 1573-5079
    Keywords: activation ; deactivation ; induction ; irradiance ; kinetics ; photosynthesis ; phytoplankton ; Rubisco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was examined in three marine microalgae: the chlorophyte t Dunaliella tertiolecta and the chromophytes t Pavlova lutheri and t Thalassiosira pseudonana. The three species differed in the sensitivity of Rubisco activity in crude extracts to magnesium ion concentration, the presence of protease inhibitors, the duration of the incubation on activity, and the potential for full activation of Rubisco with 20 mM magnesium chloride and 20 mM bicarbonate t in vitro. t D. tertiolecta had responses that were similar to those described in vascular plants: regulation of initial activity on a gradient of irradiances; maximum initial activities that were 80– 90% of light-saturated photosynthesis; total activities that exceeded light-saturated photosynthesis by 30–100%; and deactivation of Rubisco in darkness. Both initial and total activity declined in darkness and increased on a return to growth irradiance. First-order time constants were about 9 min for deactivation and 3 min for reactivation of initial activity. The decline in total activity after a transition into darkness could not be reversed t in vitro but could be reversed by exposing t D. tertiolecta to light, a characteristic of regulation by CA1P. The responses of t T. pseudonana were qualitatively similar, except that recovery of initial activity was low and could only account for 30–40% of light-saturated photosynthesis. Rubisco from t T. pseudonana exposed to low irradiance could be activated t in vitro but at growth irradiance and higher, total activity was lower than initial activity. The time constants for deactivation and reactivation of initial activity after reciprocal switches between growth irradiance and darkness were 12–18 min and 3 min in t T. pseudonana. t P. lutheri showed no regulation of Rubisco activity in response to changes in irradiance or light-dark transitions. This may have been an artifact of the conditions chosen to measure activity.
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    Can photosynthesis respond to short-term fluctuations in atmospheric carbon dioxide? (1997)
    Springer
    Photosynthesis research 51 (1997), S. 179-184 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; FACE ; global change ; photosynthesis ; Photosystem II ; quantum yield ; quenching analysis ; rising CO2 concentration ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rapid and irregular variations of atmospheric CO2 concentrations (ca) occur in nature but are often very much more pronounced and frequent when artificially enriching CO2 concentrations in simulating the future atmosphere. Therefore, there is the danger that plant responses at elevated CO2 in fumigation experiments might reflect the increased frequency and amplitude of fluctuation in concentration as well as the increase in average concentration. Tests were conducted to determine whether the photosynthetic process could sense such fluctuations in ca. Instantaneous chlorophyll fluorescence (Ft) was monitored for wheat leaves (Triticum aestivum cv. Hereward) exposed to ca oscillating symmetrically by 225 μmol mol-1 about a ca set point concentration of 575 or 650 μmol mol-1. No Ft response was detected to half-cycle step changes in ca lasting less than two seconds, but at half-cycles of two seconds or longer, the response of Ft was pronounced. In order to determine the in vivo linear electron transport rate (J) the O2 concentration was maintained at 21 mmol mol-1 to eliminate photorespiration. J which is directly proportional to the rate of CO2 uptake under these conditions, was not significantly changed at half-cycles of 30 s or less but was decreased by half-cycles of 60 s or longer. It was inferred that if duration of an oscillation is less than 1 minute and is symmetrical with respect to mean CO2 concentration, then there is no effect on current carbon uptake, but oscillations of 1 minute or more decrease photosynthetic CO2 uptake in wheat.
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    Increases in the fluorescence Fo level and reversible inhibition of Photosystem II reaction center by high-temperature treatments in higher plants (1997)
    Springer
    Photosynthesis research 52 (1997), S. 57-64 
    Details
    ISSN: 1573-5079
    Keywords: Fm ; high-temperature stress ; pheophytin a ; photosynthesis ; Qa ; spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of high temperatures on the fluorescence Fm (maximum fluorescence) and Fo (dark level fluorescence) levels were studied and compared with those of the photochemical reactions of PS II. These comparisons were performed during and after the high temperature treatments. The following results were obtained; (1) increases in the Fo level at high temperatures were partly reversible, (2) the Fm level in the presence of dithionite in spinach chloroplasts decreased at high temperatures and also showed a partial reversibility, (3) photoreductions of pheophytin a and Qa were reversibly inhibited at high temperatures parallel to the decrease in the difference between the Fm and Fo levels, and (4) the decrease in the fluorescence Fm level seemed to be related to denaturation of chlorophyll-proteins. All the data suggested that, as well as the separation of light-harvesting chlorophyll a/t b protein complexes of PS II from the PS II core complexes, partly reversible inactivation of the PS II reaction center at high temperatures is the cause of the increase in the Fo level.
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    A method for measuring whole plant photosynthesis in Arabidopsis thaliana (1997)
    Springer
    Photosynthesis research 52 (1997), S. 263-269 
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    ISSN: 1573-5079
    Keywords: Arabidopsis ; chlorophyll fluorescence ; gas exchange ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurement of photosynthesis of intact leaves of Arabidopsis thaliana has been prohibitive due to the small leaf size and prostrate growth habit. Because of the widespread use of Arabidopsis for plant science research it is important to have a procedure for accurate, nondestructive measurement of its photosynthesis. We developed and tested a method for analysis of photosynthesis in whole plants of Arabidopsis. Net carbon assimilation and stomatal conductance were measured with an open gas exchange system and photosynthetic oxygen evolution was determined from chlorophyll fluorescence parameters. Individual plants were grown in 50 cubic centimeter tubes that were attached with an air tight seal to an enclosed gas exchange chamber for measurement of carbon dioxide and water exchange by the whole plant. Chlorophyll fluorescence from intact leaves was simultaneously measured with a pulse modulated fluorometer. Photosynthetic CO2 assimilation and stomatal conductance rates were calculated with established gas exchange procedures and O2 evolution was determined from chlorophyll fluorescence measurement of Photosystem II yield. Carbon assimilation and oxygen evolution in response to light intensity and ambient CO2 concentration was measured and is presented here to demonstrate the potential use of this method for investigation of photosynthesis of Arabidopsis plants in controlled environment conditions.
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    URL: http://dx.doi.org/10.1023/A:1005834327441
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    Multiple strategies for a high light existence in a tropical marine macroalga (1997)
    Springer
    Photosynthesis research 53 (1997), S. 149-159 
    Details
    ISSN: 1573-5079
    Keywords: Chlorodesmis fastigiata ; D1 protein ; fluorescence ; macroalgae ; photoinhibition ; photosynthesis ; Photosystem II heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acclimation to high light conditions on the top of coral reefs was examined in the coenocytic, filamentous green macroalga Chlorodesmis fastigiata (C. Ag.) Ducker. Despite having a pool of violaxanthin, high light does not induce formation of zeaxanthin in this macroalga. Exposure to 11 and 33% of surface irradiance resulted in parallel, reversible declines in Fv/Fmand in the number of functional PSII centers. The quantum requirement for PSII inactivation was calculated to be approx. 2×107photons. Recovery of PSII activity after low photon exposures did not depend on protein synthesis, unlike at higher photon exposures, where recovery was inhibited by 50% in the presence of lincomycin. Accumulation of inactive, quenching PSII centers is proposed as a mechanism of energy dissipation; only some of these centers require protein synthesis for reactivation. In natural-sized populations, midday photoinhibition was greater in filament tips than in bases, but the number of inactive PSII centers within entire filaments did not significantly change over the course of the day. It is proposed that the higher chlorophyll concentration in the tips provides protective shading to chloroplasts in lower regions, and that cytoplasmic streaming of chloroplasts within this siphonous alga limits the cumulative exposure to high light, thereby providing another level of protection from high light stress.
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    URL: http://dx.doi.org/10.1023/A:1005820203585
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    Mutation in a novel gene required for photomixotrophic growth leads to enhanced photoautotrophic growth of Synechocystis sp. PCC 6803 (1997)
    Springer
    Photosynthesis research 53 (1997), S. 243-252 
    Details
    ISSN: 1573-5079
    Keywords: cyanobacteria ; evolution ; glucose-sensitivity ; photoacclimation ; photosynthesis ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the glucose-tolerant strain of Synechocystis sp. PCC 6803, we found two types of cells with distinct growth properties. Under photoautotrophic conditions at any light intensity, one type gave larger colonies (designated WL) than the other (designated WS). Notably, the WL cells produced much larger colonies than the WS cells at higher light intensity. In contrast, growth of the WL cells was severely suppressed under mixotrophic conditions with glucose and light, while the WS cells grew normally. A gene which could complement the WL phenotype was obtained from a wild-type genomic library. The gene, designated pmgA, coded for a 23 kDa polypeptide of 204 amino acid residues with no apparent homology to known genes. In the WL genome, the base substitution of T for C at position 193 of pmgA caused replacement of Leu with Phe at position 65 of the product. The phenotype of pmgA disruption mutants was similar to that of the WL cells, indicating that the WS cells expressed a functional pmgA product. By direct sequencing of polymerase chain reaction-amplified pmgA from genomic DNA, it was revealed as an example of microevolution that WL had expelled WS from the photoautotrophic culture of wild-type in our laboratory for a year or so. Mixed culture in liquid also demonstrated that the WL cells increased gradually under photoautotrophic conditions, while they decreased rapidly under photomixotrophic conditions. These results suggest that pmgA product is essential for photomixotrophic growth, whereas it represses photoautotrophic growth. To our knowledge, the WL cells and pmgA-disrupted mutants are the first in cyanobacteria, which shows much improved photosynthetic growth than wild-type especially at high light intensity.
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    URL: http://dx.doi.org/10.1023/A:1005879905365
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    Foliar CO2photoassimilation and chloroplast linear electron transport rates in nitrogen-sufficient and nitrogen-limited soybean plants (1997)
    Springer
    Photosynthesis research 54 (1997), S. 209-217 
    Details
    ISSN: 1573-5079
    Keywords: ferredoxin, NADP photoreduction ; nitrogen limitation ; non cyclic electron transport ; photosynthesis ; Photosystem 1 and 2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaflets of soybean plants which are moderately inorganic nitrogen (N)-limited exhibit either no difference in the rate of net photosynthesis or as much as a 15–23% lower net photosynthesis rate per unit area than leaflets of N-sufficient plants [Robinson JM (1996) Photosynth Res 50: 133–148; Robinson JM (1997a) Int J Plant Sci 158: 32–43]. However, mature leaflets of N-limited soybean plants have a higher CO2photoassimilation rate per unit chlorophyll than leaflets of N-sufficient soybean plants at both moderate light intensity (≈500 µmol m-2s-1) and saturating light intensity (≈1200 µmol m-2s-1) [Robinson JM (1996) Photosynth Res 50: 133–148]. This study was undertaken to determine whether chloroplast thylakoids isolated from the leaflets of nitrogen-limited soybean plants displayed similar or higher linear electron transport rates (H2O → ferredoxin → NADP) per unit chlorophyll than thylakoids isolated from leaflets of N-sufficient plants. Chlorophyll concentration in reaction mixtures containing chloroplast thylakoids prepared from leaflets of N-limited plants was manipulated so that it was similar to the chlorophyll concentration in reaction mixtures of thylakoids prepared from leaflets of N-sufficient plants. Measurements of ferredoxin dependent, NADP dependent, O2photo-evolution in thylakoid isolates were carried out in saturating light (≈1500 µmol m-2s-1) and with $$NH_4^ + $$ (an uncoupler) in the chloroplast reaction mixtures. Chloroplast thylakoids isolated from N-limited soybean plant leaflets routinely had a 1.5 to 1.7 times higher rate of uncoupled, whole chain electron transport per unit chlorophyll in saturating light than did chloroplast thylakoids isolated from leaflets of N-sufficient plants. The results suggest that the photosystems and photosynthetic electron transport chain components are more active per unit Chl in leaflet chloroplast thylakoids of N-limited soybean plants than in thylakoids of N-sufficient plants.
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    URL: http://dx.doi.org/10.1023/A:1005995718710
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    Analysis of the chloroplast protein complexes by blue-native polyacrylamide gel electrophoresis (BN-PAGE) (1997)
    Springer
    Photosynthesis research 53 (1997), S. 35-44 
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    ISSN: 1573-5079
    Keywords: b 6 f complex ; chloroplast ATP synthase ; light-harvesting complexes ; photosynthesis ; photosystems ; ribulose-bisphosphate carboxylase/oxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Blue-native polyacrylamide gel electrophoresis (BN-PAGE) is a powerful procedure for the separation and characterization of the protein complexes from mitochondria. Membrane proteins are solubilized in the presence of aminocaproic acid and n-dodecylmaltoside and Coomassie-dyes are utilized before electrophoresis to introduce a charge shift on proteins. Here, we report a modification of the procedure for the analysis of chloroplast protein complexes. The two photosystems, the light-harvesting complexes, the ATP synthase, the cytochrome b 6 f complex and the ribulose-bisphosphate carboxylase/oxygenase are well resolved. Analysis of the protein complexes on a second gel dimension under denaturing conditions allows separation of more than 50 different proteins which are part of chloroplast multi-subunit enzymes. The resolution capacity of the blue-native gels is very high if compared to 'native green gel systems' published previously. N-terminal amino acid sequences of single subunits can be directly determined by cyclic Edman degradation as demonstrated for eight proteins. Analysis of chloroplast protein complexes by blue-native gel electrophoresis will allow the generation of 'protein maps' from different species, tissues and developmental stages or from mutant organelles. Further applications of blue-native gel electrophoresis are discussed.
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    URL: http://dx.doi.org/10.1023/A:1005882406718
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    Determination of the quenching efficiency of the oxidized primary donor of Photosystem I, P700+: Implications for the trapping mechanism (1997)
    Springer
    Photosynthesis research 54 (1997), S. 237-240 
    Details
    ISSN: 1573-5079
    Keywords: fluorescence induction ; fluorescence yield ; photosynthesis ; P700 ; internal conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005981016835
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    Responses of Rubisco activation and deactivation rates to variations in growth-light conditions (1997)
    Springer
    Photosynthesis research 52 (1997), S. 117-125 
    Details
    ISSN: 1573-5079
    Keywords: gas exchange ; light acclimation ; photosynthesis ; sunflecks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Basil (Ocimum basilicum) and impatiens (Impatiens wallerana) were grown in sun, shade, or fluctuating light (15 min sun, 15 min shade) to examine the effects of growth-light conditions on the rates of light-induced Rubisco activation and deactivation. Rubisco activation and deactivation rates were determined from gas-exchange measurements of photosynthesis following a step increase in PFD. Rubisco deactivation rates were also determined from biochemical analyses of leaf extracts. There were no significant differences in Rubisco activation rate among the growth conditions or between the two species. However, there were significant differences in Rubisco deactivation rate among the growth conditions in basil and between the two species. In basil, Rubisco deactivated more slowly following a decrease in PFD in sun- and fluctuating-light grown plants than in shade grown plants. Slower rates of Rubisco deactivation during periods at low PFD resulted in higher activation states at the onset of increased PFD. Thus, the contribution of Rubisco activation to the induction process was less for basil plants grown under sun and fluctuating light than for those grown under shade. Impatiens deactivated Rubisco more rapidly than in basil, but there was no substantial effect of the three growth-light conditions on Rubisco deactivation rates in impatiens.
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    URL: http://dx.doi.org/10.1023/A:1005847500471
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    Geochemistry and acidity of sulphide-bearing postglacial sediments of western Finland (1997)
    Springer
    Environmental geochemistry and health 19 (1997), S. 155-164 
    Details
    ISSN: 1573-2983
    Keywords: geochemistry ; metals ; sulphide sediment ; oxidation ; acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Medicine
    Notes: Abstract The geochemistry, mineralogy, acidity and electric conductivity of sulphide-bearing postglacial sediments located on the coastal plains of western Finland were studied. Grain size and mineralogical analysis (eight samples studied) indicated that the sediments are silts dominated by primary minerals (quartz, feldspars), and that the clay fraction (〈2µm), which made up less than one-third of the bulk samples, is enriched in phyllosilicates but depleted in quartz and feldspars, relative to bulk samples. As compared to the metal contents of the fine-fraction of glacial till (data of the Geological Survey of Finland), the fine sediments appear to be enriched in sulphur (median = 0.54%) and trace metals such as Ni (31 µg g−1), Zn (90 µg g−1), Co (13 µg g−1), Cr (48 µg g−1) and V (50 µg g−1). Statistical analysis indicated that aluminosilicates are the principal carrier phases of trace metals, and that sulphides and organic matter only partially control the distribution of elements other than S and C. A 3-g portion of 232 samples was oxidised in the laboratory by atmospheric oxygen for a period of 1 year. After this period of oxidation, 15 ml of water was added, after which pH and electric conductivity of the suspensions (sediment:water, 1:5) were measured. The quantities of elements mobilised by the oxidation was calculated from the dissolved concentrations found in 3 g of oxidised sediment suspended in 30 ml of deionised water (eight samples studied). The results of the experiment showed that the impact of sulphide oxidation on the pH and conductivity of the sediments is large, and that a high proportion (〉13%) of the aqua-regia extractable contents of several elements (Co, Mn, Ca, Ni, Zn, Sr, Na and B) are mobilised at oxidation. Because of the high quantities of acidity and metals liberated at oxidation, it is argued that stream-water quality, which is poor in the study area, will not improve unless artificial draining is restricted in areas of sulphide sediments.
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    URL: http://dx.doi.org/10.1023/A:1018462824486
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    Gas-phase catalytic oxidation ofm-xylene (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 117-120 
    Details
    ISSN: 1588-2837
    Keywords: m-xylene ; oxidation ; gas-phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The gas-phase oxidation ofm-xylene on catalysts for partial hydrocarbon oxidation (Bi−Fe−Co−Ni−Mo−P−O, V−Sb−O and V−Ti−O) has been studied at 325–400°C. 3-Methylbenzaldehyde (for the first two catalysts), or both 3-methylbenzaldehyde and 3-methylbenzoic acid (for the last one) were shown to be the main partial oxidation products.
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    URL: http://dx.doi.org/10.1007/BF02475721
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    Kinetic study of methane oxidation over perovskite oxides La1−xSrxCoO3 (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 185-190 
    Details
    ISSN: 1588-2837
    Keywords: Methane ; oxidation ; La1−xSrxCoO3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methane oxidation over perovskite oxide (La1−xSrxCoO3) were investigated under rich oxygen circumstance. The large x in oxide or the higher temperature will promote the lattice oxygen to participate in the reaction. The relative adsorption properties of catalyst and reaction kinetic were also studied.
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    URL: http://dx.doi.org/10.1007/BF02475731
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    Effect of structural disorder on the catalytic activity of mixed La−Sr−Co−Fr−O perovskites (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 129-135 
    Details
    ISSN: 1588-2837
    Keywords: Perovskite ; defect structure ; carbon monoxide ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract For a perovskite system La0.7Sr0.3Co1-xFexO3, the effect of partial substitution of Co by Fe on the particle microstructure and chemical composition of the surface layer has been studied. Iron incorporation was found to cause a structure rearrangement from the hexagonal (at x〈0.05) to the cubic (atx〉0.05) type, which was not accompanied by any appreciable variation of the surface layer composition. A transient sample with x=0.05 was characterized by a high degree of misorientation of microblocks and had the highest activity in the CO catalytic oxidation.
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    URL: http://dx.doi.org/10.1007/BF02475723
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    Zirconium(IV) catalysis in perborate oxidation of iodide (1997)
    Springer
    Reaction kinetics and catalysis letters 60 (1997), S. 387-394 
    Details
    ISSN: 1588-2837
    Keywords: Perborate ; iodide ; zirconium(IV) ; catalysis ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zirconium(IV) catalyzes perborate oxidation of iodide ion. In acidic solution the oxidation is zero order with respect to perborate, first order with respect to Zr(IV), independent of [H+] and exhibits Michaelis-Menten dependence on [I−]. Mechanistic pathway of the catalysis is discussed and a rate equation is derived.
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    URL: http://dx.doi.org/10.1007/BF02475703
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    Recovery of net CO2 assimilation after heat stress is correlated with recovery of oxygen-evolving-complex proteins in Zea mays L. (1997)
    Springer
    Photosynthetica 34 (1997), S. 13-20 
    Details
    ISSN: 1573-9058
    Keywords: D1 protein ; internal CO2 concentration ; maize ; oxygen evolution ; phosphoenolpyruvate carboxylase ; photosynthesis ; photosystem 2 ; ribulose-1,5-bisphophate carboxylase/oxygenase ; stomatal conductance ; thermotolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosystem 2 (PS2) in general, and the oxygen-evolving complex (OEC) in particular, is one of the most thermolabile components of photosynthesis. We examined the effects of heat stress on net photosynthetic rate (PN) and content of several stromal and thylakoid-membrane proteins (including OEC proteins) in maize (Zea mays L.) in order to determine if decreases in PN during, and especially after, heat stress were correlated with decreases in the content of OEC proteins. The PN decreased with heat stress in maize, and post-heat stress recovery of PN required 4 d following the second of two heat-shocks. The decrease in PN was not the result of stomatal closure. Cellular levels of the 33, 23, and 16 kDa OEC proteins decreased with heat stress, and the decreases were greatest and most closely correlated with decreases in PN for OEC16. Following the second heat stress, full recovery of OEC levels (especially OEC16 and 33) coincided with full recovery of PN, more so than with other photosynthetic proteins examined. For example, decreases in levels of the 32-kDa QB-binding protein of the PS2 reaction center (D1), ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit, and phosphoenolpyruvate carboxylase were generally smaller than for the OEC proteins and full recovery of these proteins occurred at least 2 d prior to full recovery of photosynthesis. These results are consistent with previous fluorescence and in vitro studies by others in suggesting that heat-relaed effects on PS2 and the OEC are an important limitation to Pn during heat stress. Additionally, these results suggest that heat-related decreases in the content of OEC proteins may limit post-heat stress recovery of carbon fixation.
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    URL: http://dx.doi.org/10.1023/A:1006899314677
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    Effect of cytokinins on the photosynthetic apparatus in water-stressed and rehydrated bean plants (1997)
    Springer
    Photosynthetica 34 (1997), S. 563-567 
    Details
    ISSN: 1573-9058
    Keywords: oxygen flash yields ; photochemical activity ; photosynthesis ; photosystem 2 ; thermoluminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of the cytokinins 6-benzylaminopurine (BAP) and N-2-chloro-4-pyridyl-N′-phenylurea (4-PU-30) on the photochemical activity, oxygen flash yields, and thermoluminescence in bean plants under a water stress were studied. The cytokinins increased the photochemical (Hill reaction) activity and thermoluminescence "B"-band in control as well as in stressed and rehydrated plants, while the oxygen flash yields were affected only in the stressed and rehydrated plants.
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    URL: http://dx.doi.org/10.1023/A:1006821730974
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    Effect of fruiting and drought or flooding on carbon balance of apple trees (1997)
    Springer
    Photosynthetica 33 (1997), S. 269-275 
    Details
    ISSN: 1573-9058
    Keywords: Malus domestica ; open-top cuvettes ; photosynthesis ; respiration ; water stress ; water use efficiency ; xylem water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of fruiting or deblossomed trees to water stress such as drought or flooding was investigated in six semi open-top cuvettes each containing one apple (Malus domestica Borkh. cv. Golden Delicious) tree. Xylem water potentials of leaves dropped from -1.2 to -4.1 MPa within 7 d of drought, the effect being enhanced by fruiting. Apple trees without fruits showed smaller reductions in net photosynthetic rate (P N ) and dark respiration rate (R D ) after 2 d of drought and hence more positive carbon balances relative to fruiting trees. Flooding for 4 d had a more pronounced effect on P N than on transpiration, resulting in a reduced water use efficiency (WUE). This reduction in WUE was greater in the non-fruiting trees. Flooding reduced P N of the whole apple canopies irrespective of fruiting; aple trees without fruits increased R D resulting in a less positive carbon balance relative to fruiting trees. Fruiting increased the sensitivity to drought of apple trees (R D and P N ), but decreased their sensitivity to flooding (R D and WUE), suggesting different adaptation mechanisms for the two forms of water stress.
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    URL: http://dx.doi.org/10.1023/A:1022172515878
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    Picosecond fluorescence decay studies on water-stressed pea leaves: energy transfer and quenching processes in photosystem 2 (1997)
    Springer
    Photosynthetica 34 (1997), S. 97-106 
    Details
    ISSN: 1573-9058
    Keywords: chlorophyll ; DCMU ; exciton-radical pair equilibrium model ; NH2OH ; photosynthesis ; Pisum ; quinones ; relative air humidity ; wilting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Detached leaves of pea (Pisum sativum) were submitted to water stress at different relative air humidities. The photosynthetic activity of photosystem 2 (PS2) was monitored by time-resolved picosecond chlorophyll (Chl) fluorescence spectroscopy. In the first days the well-known fast Chl fluorescence decay was observed which indicated high PS2 activity. After a few days the average fluorescence decay time τm reached a maximum, depending on the wilting conditions, but always at a relative loss of leaf mass of 80%. After this maximum, τm decreased within a few hours, the fluorescence decay became similar to that one of an intact leaf, but an additional fluorescence decay component with a lifetime of 3.6 ns appeared. At first the primary quinone QA was reduced due to inhibition of the electron transfer to the secondary quinone QB. Simultaneously, water deficiency caused an electron lack at the oxidizing site of PS2. This disabled the primary electron donor of PS2, tyrosine Z, from reducing the oxidized reaction centre of PS2 (P680+). Thus a recombination of P680+-pheophytin-QA- took place, and the energy was lost as heat. With further water stress, QA was decoupled from PS2. The new fluorescence decay component could therefore be assigned to energetically decoupled antenna complexes.
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    Short-term effects of aluminium at alkaline pH on the structure and function of the photosynthetic apparatus (1997)
    Springer
    Photosynthetica 34 (1997), S. 169-177 
    Details
    ISSN: 1573-9058
    Keywords: chlorophyll fluorescence ; chloroplast ultrastructure ; photosynthesis ; photosystem 2 ; Thinopyrum bessarabicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 24 h exposure of the salt-tolerant grass Thinopyrum bessarabicum (Savul. and Rayss) A. Love seedlings to 1 mM aluminium (Al) in nutrient solution at pH of 9.0 resulted in a significant reduction of the biomass. In control samples the mesophyll chloroplasts exhibited the usual lens shape with most grana arranged in straight or slightly curving lines, and only 6.5 % of the grana were out of order. In Al-treated plants the mesophyll chloroplasts displayed a slightly distorted shape and distended size with most grana arranged in bow-like lines, while in the central region of the organelle as many as 26.7 % of the grana were independent and out of order in relation to the long axis. The morphological changes in the chloroplast shape and grana arrangement were probably due to swelling and distension of the chloroplasts in consequence to the altered membrane permeability. The initial in vivo chlorophyll (Chl) fluorescence FO, as well as the intermediate FI and peak fluorescence FP were increased under the Al stress: this indicated a destruction of photosystem (PS) 2 reaction centres and increased reduction of QA. The (FI-FO)/(FP-FO) ratio exhibited a significant increase indicating higher proportion of PS2 centres unable to reduce QB. Changes in the chloroplast ultrastructure seemed to be the reason of photosynthetic electron transport inhibition. Yet all these changes in the photosynthetic performance and chloroplast ultrastructure were considered as indirect effects of Al treatment since Al concentration in the leaves was undetectable. Disturbances in the chloroplast ultrastructure could be caused by a reduced uptake and/or transport of other nutrients.
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    URL: http://dx.doi.org/10.1023/A:1006880205108
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    Planting density effects on assimilation and partitioning of photosynthates during grain filling in the late-sown wheat (1997)
    Springer
    Photosynthetica 33 (1997), S. 199-204 
    Details
    ISSN: 1573-9058
    Keywords: photosynthates ; 14CO2 ; ear ; leaf insertion ; photosynthesis ; Triticum aestivum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf blades of the late-sown winter wheat produced the major portion, i.e., more than 60 %, of the total 14C-photosynthates at grain filling, but ear (rachis and glumes) only about 15 %, sheaths about 11 %, and stem internodes about 11 %. The change of plant density in this experiment had little influence on the 14CO2-photoassimilation of the ear (rachis and glumes), flag leaf lamina, sheaths and stem internodes, but markedly affected photosynthesis of the second, the third and lower leaves. The photosynthetic rate [expressed as specific radioactivity, s-1 kg-1(d.m.)] and the amount of 14CO2 photosynthates decreased significantly in the second, the third and other lower leaves at a high plant density. Upon grain-filling of the late-sown wheat, the grain was the major importer of photosynthates. Yet partitioning to the stem internodes depended on the plant density. Stem was the importer of photosynthates at a low plant density, but the exporter at a high plant density. In plants at a low plant density a fairly large proportion of photosynthates was distributed into the roots. The middle and lower above-ground parts of the late-sown wheat at a high plant density decreased or lost their function early. As a result, the plant senesced earlier. However, the grain setting, filling and yielding were restricted. An appropriately low plant density was suitable for prolonging the function of the middle and lower organs, delaying the senescence of plant, increasing the source supply for grain filling, and improving the grain yield.
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    Phosphate uptake by phosphorus-starved cells of the cyanobacterium Phormidium laminosum (1997)
    Springer
    World journal of microbiology and biotechnology 13 (1997), S. 699-705 
    Details
    ISSN: 1573-0972
    Keywords: Phormidium laminosum ; phosphate uptake ; phosphorus-starved ; photosynthesis ; vanadate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Phosphorus(P)-starved cells of the cyanobacterium Phormidium laminosum have been investigated in relation to their phosphate uptake characteristics. P-deficient cells showed much higher phosphate uptake rates from ultrapure water supplemented with this anion than P-sufficient ones. After 9 days of starvation in P-free medium, the total cellular P content of P-deficient cells was approximately five times lower than that of cells grown in the presence of phosphate. Phosphate uptake by P-deficient cells occurred in both light and dark under aerobic conditions. In anaerobiosis, light was required for uptake, suggesting that the necessary energy could be derived from the respiratory electron transport chain. Phosphate uptake in P-deficient cells was sensitive to vanadate, suggesting the involvement of a plasma membrane ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018583224294
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  • 90
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    Ultrastructural changes in gametophytes of Acrostichum aureum L. cultured in different sodium chloride concentrations (1997)
    Springer
    Biologia plantarum 39 (1997), S. 607-614 
    Details
    ISSN: 1573-8264
    Keywords: chloroplasts ; fern ; mitochondria ; photosynthesis ; respiration ; salt stress ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gametophytes cultured in solutions containing 0.0 to 0.7 % NaCl exhibited no change in ultra structural organization of chloroplasts. In 1.0% NaCl-grown gametophytes, there were thinner granal stacks, relatively larger spaces between granal thylakoidal membranes and larger plastoglobuli in the chloroplasts. These changes were accompanied by a decrease in photosynthesis. Cup shape, horseshoe shape, ring shape, and amoeboid mitochondria were observed in gametophytes grown in 0.0 to 0.7% NaCl. Only round mitochondria were observed in the gametophytes grown in 1.0 % NaCl. Mitochondria seemed to be more resistant to salt stress compared to chloroplasts. There was no direct relationship between changes in respiration rate and changes in mitochondrial shape among gametophytes grown in different NaCl concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000939017348
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  • 91
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    Control of PAR-saturated CO2 exchange rate in some C3 and CAM plants (1997)
    Springer
    Biologia plantarum 40 (1997), S. 91-101 
    Details
    ISSN: 1573-8264
    Keywords: CER ; leaf thickness ; photosynthesis ; photosynthetic N-use efficiency succulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We measured PAR-saturated CO2 exchange rate (CER), and leaf N, P and chlorophyll (Chl) concentrations in 21 plant species, selected to encompass as broad a range in specific leaf area (SLA) as possible, and encompassing non-succulent C3 as well as succulent CAM plants. We worked with plants growing under uniform conditions in the facilities of a biological research station to ensure that any correlations found were due to inherent, genetically controlled, relationships between the measured parameters and not due to variations in resource availability in different habitats. We found CER to be strongly correlated to SLA, leaf N concentration and Chl concentration. CER increased much faster with increasing leaf N concentration (CER ≈ N3.1) than with increasing SLA (CER ≈ SLA1.2). CER also increased much faster with leaf N concentration than with increasing Chl concentration (CER ≈ Chl1.3), indicating the photosynthetic N-use efficiency (NUE) to be higher for plants with high N concentration than for plants with low N concentration (NUE ≈ N2.1). Analysis of covariance showed that these relationships exist even when comparing plants of widely different growth forms - succulent or non-succulent, and of different photosynthetic pathways, as the C3 and CAM plants compared here. Testing against scaling coefficients calculated using dimensional analysis, showed that the scaling of N, Chl and CER against SLA was not merely a result of diluting N and Chl with carbon in thicker leaves but that SLA, probably through influencing light absorptio and/or CO2 diffusion pathway, played an independent role in controlling CER.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000900718932
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