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  • Chemistry  (18)
  • LUNAR AND PLANETARY EXPLORATION  (12)
  • Chlorophyll fluorescence  (4)
  • Astrophysics
  • EARTH RESOURCES AND REMOTE SENSING
  • 1985-1989  (36)
  • 1
    Electronic Resource
    Electronic Resource
    Studies on the limitations to photosynthesis in leaves of the atrazine-resistant mutant ofSenecio vulgaris L. (1988)
    Springer
    Planta 173 (1988), S. 459-467 
    Details
    ISSN: 1432-2048
    Keywords: Atrazine ; Carbon assimilation ; Chlorophyll fluorescence ; Herbicide resistance ; Mutant (atrazine resistant) ; Photosynthesis in atrazine resistant mutant ; Senecio (atrazine, mutant)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In leaves of an atrazine-resistant mutant ofSenecio vulgaris the quantum efficiency of CO2 assimilation was reduced by 21% compared to the atrazine-susceptible wild type, and at a light level twice that required to saturate photosynthesis in the wild type the CO2 fixation rate in the mutant was decreased by 15%. In leaves at steady-state photosynthesis there was a measurable increase in the reduction state of the photosystem II (PSII) primary quinone acceptor,Q A. Although this would lead to a decreased rate of PSII electron transport and may thus explain the decrease in quantum efficiency, this cannot account for the fall in the maximum rate of CO2 fixation. The atrazine-resistant mutant showed an appreciably longer photosynthetic induction time which indicates an effect on carbon metabolism; however, the response of CO2-fixation rate to intercellular CO2 concentration revealed no differences in carboxylation efficiency. There were also no differences in the ability to perform a State 1–State 2 transition between the atrazine-resistant and susceptible biotypes and no difference in the profiles of phosphorylated thylakoid polypeptides. It is concluded that the alteration of the redox equilibrium between PSII quinone electron acceptors in the atrazine-resistant biotype limits appreciably the photosynthetic efficiency in non-saturating light. Additionally, there is a further, as yet unidentified, limitation which decreases photosynthesis in the resistant mutant under light-saturating conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00958958
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of ionic stress on photosynthesis in Dunaliella tertiolecta (1985)
    Springer
    Planta 163 (1985), S. 250-256 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Dunaliella (osmoregulation) ; Osmoregulation ; Photosynthesis (ionic stress)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparison of the effects of ionic stress and an uncoupler on long-term fluorescence transients (the ‘Kautsky effect’) in the green alga Dunaliella tertiolecta indicated that the large quenching induced by ionic stress was caused by a pH gradient across the thylakoid membrane. This possiblity was given support by the increase in the slow phase of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in algae subjected to ionic stress. Low-temperature fluorescence emission spectra indicated that salt stress enhanced photosystem-I emission in the dark, and a comparison of simultaneous emissions at 695 and 720 nm at room temperature indicated a further increase in photosystem-I emission during the fluorescence transients. Taken together with the decrease in the fast phase of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in stressed algae, our results indicate that ionic stress stimulates cyclic electron flow, and that non-cyclic flow is inhibited. The effect of sucrose-induced osmotic stress was similar to, but less marked than, the effects of NaCl and KCl; the effect of decreasing the external salinity was small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393515
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  • 3
    Electronic Resource
    Electronic Resource
    Some effects of 4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone (San 9785) on the development of chloroplast thylakoid membranes in Hordeum vulgare L. (1985)
    Springer
    Planta 165 (1985), S. 277-283 
    Details
    ISSN: 1432-2048
    Keywords: 4-Chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone ; Chlorophyll fluorescence ; Hordeum (thylakoids) ; Linolenic acid ; San 9785 ; Thylakoid (organisation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloroplast ultrastructural and photochemical features were examined in 6-d-old barley (Hordeum vulgare L. cv. Sundance) plants which had developed in the presence of 4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone (San 9785). In spite of a substantial modification of the fatty-acid composition of thylakoid lipids there were no gross abnormalities in chloroplast morphology, and normal amounts of membrane and chlorophyll were present. Fluorescence kinetics at 77K demonstrated considerable energetic interaction of photosystem (PS)I and PSII chlorophylls within the altered lipid environment. An interference with electron transport was indicated from altered room-temperature fluorescence kinetics at 20°C. Subtle changes in the arrangements of chloroplast membranes were consistently evident and the overall effects of these changes was to increase the proportion of appressed to nonappressed membranes. This correlated with a lower chlorophyll a/b ratio, an increase in the amount of light-harvesting chlorophylls as determined by gel electrophoresis and fluorescence emission spectra, and an increase in excitation-energy transfer from PSII to PSI, as predicted from current ideas on the organisation of photosystems in appressed and non-appressed thylakoid membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395051
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  • 4
    Electronic Resource
    Electronic Resource
    The role of carbon dioxide and oxygen in determining chlorophyll fluorescence quenching during leaf development (1985)
    Springer
    Planta 165 (1985), S. 477-485 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Leaf development (photosynthesis) ; Photoinhibition ; Triticum ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorophyll fluorescence emission at 680 nm (F680) and the rate of CO2 fixation were measured simultaneously in sections along the length of wheat and maize leaves. These leaves possess a basal meristem and show a gradation in development towards the leaf tip. The redox state of the primary electron acceptor, Q, of photosystem II was estimated using a non-invasive method. Distal mature leaf sections displayed typical F680 induction curves which were generally anti-parallel with CO2 fixation and during which Q became gradually oxidised. In leaf-base sections net assimilation of CO2 was not detectable, F680 quenched slowly and monotonously without displaying any of the oscillations typical of mature tissue and Q remained relatively reduced. Sections cut from mid-regions of the leaf showed intermediate characteristics. There were no major differences between the wheat and maize leaf in the parameters measured. The results support the hypothesis that generation of the transthylakoid proton gradient and associated ATP production is not a major limitation to photosynthesis during leaf development in either C3 or C4 plants. Removal of CO2 from the mature leaf sections caused little change in steady-state F680 and produced about 50% reduction of Q. When O2 was then removed, F680 rose sharply and Q became almost totally reduced. In immature tissue unable to assimilate CO2, removal of O2 alone caused a similar large rise in F680 and reduction of Q whilst removal of CO2 had negligible effects on F680 and the redox state of Q. It is concluded that in leaf tissue unable to assimilate CO2, either because CO2 is absent or the tissue is immature, O2 acts as an electron acceptor and maintains Q in a partially oxidised state. The important implication that O2 may have a role in the prevention of photoinhibition of the photochemical apparatus in the developing leaf is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398092
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  • 5
    Electronic Resource
    Electronic Resource
    Thermospray mass spectroscopy/high performance liquid chromatographic identification of the metabolites formed from arteether using a rat liver microsome preparation (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 337-351 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray LC/MS methods with internal standardization were developed for the quantification of the antimalarial arteether and six of its metabolites at the 1-10 μg/ml level in liver microsome preparations without the use of solvent extraction. The thermospray mass spectra of arteether and most of its metabolites exhibited strong [M + NH4]+ and [M - OR]+ peaks arising from the molecular ion adduct and the loss of the alkoxy or hydroxy group of the side chain. In addition to the six metabolites for which authentic reference standards were available, three additional metabolites were detected. The major metabolites of arteether were found to be dihydroartemisinin, deoxydihydroartemisinin, 3-hydroxydeoxydihydroartemisinin, two isomers of hydroxyarteether, and 3-hydroxydeoxyarteether. Deoxyartheether was not found at significant concentrations in the microsome preparation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180509
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  • 6
    Electronic Resource
    Electronic Resource
    Dilute acid hydrolysis of paper birch: Kinetics studies of xylan and acetyl-group hydrolysis (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 355-361 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch hydrolysis kinetics of paper birch (Betula papyrifera) xylan and its associated acetyl groups in dilute sulfuric acid have been measured for acid concentrations of between 0.04 and 0.18M and temperatures of between 100 and 170°C. Only 5% of the cellulose was hydrolyzed for up to 85% xylan removal. Rate data were correlated well by a parallel reaction model based on the existence of reactive and resistant xylan portions. The resulting rate equation predicts the experimental xylan concentrations in the residue to within 10%. Hydrolysis of xylan-associated acetyl groups was found to occur at the same rate as that of xylan, except at 100°C, where acetyl is released preferentially. No effect of acid concentration on the rate of acetyl removal relative to that of xylan was evident.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260270321
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  • 7
    Electronic Resource
    Electronic Resource
    Organosolv pretreatment for enzymatic hydrolysis of poplars: I. Enzyme hydrolysis of cellulosic residues (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 643-649 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aspen (Populus tremuloides) and black cottonwood (Populus trichocarpa) organosolv pulps produced in a wide range of solvent composition (between 30 and 70% by volume of methanol) and catalysts (H2SO4 and H3PO4) such that the cooking liquor pH ≤ 3 are easily digested by enzymes. The total yields of hydrolysis residues (pulps) are in the 40-60% range; the acid-catalyzed delignification followed by enzyme hydrolysis can generate 70-88% of the original six-carbon sugars contained in the wood. Glucomannan and arablnogalactan are dissolved into the pulping liquor in the pH range of 2-4.5. Lower pH (≤3) leads to additional solubilization of six-carbon sugars. These sugars may be fermented directly. From the insoluble hydrolysis residues, 36-41% conversions of wood into fermentable sugars were obtained after enzyme hydrolysis; the starting feedstocks contain 50.8 and 46.6% hexosans, respectively, for aspen and black cotton-wood. The kinetics of enzymatic hydrolysis of cellulose can be formally treated as two simultaneous pseudo-first-order reactions in which fast and slow hydrolyses of cellulose occur. Correlations between the glucan digestibility and the effect of the pretreatment have been made. The higher residual xylan content reduces the amount of the rapidly hydrolyzable glucan fraction and lowers the glucan digestibility. The proposed simple kinetic treatment is very helpful in assessing the effect of the pretreatment on pulp enzyme hydrolyzability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260310703
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  • 8
    Electronic Resource
    Electronic Resource
    A microfibril-generating factor from the cellulase of Trichoderma reesei (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 321-327 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A combination of ionic strength reduction and diafiltration of Trichoderma reesei cellulate complex through a hollow fiber apparatus of 5000 molecular weight (MW) cutoff and subsequent passage of filtrate over a Spherogel-TSK 3000-SW column provided extracts that had the ability to generate microfibrils in filter paper and to disrupt filter paper and corn leaf tissue. Milligram quantities of material obtained from these extracts released small amounts of soluble carbohydrate from filter paper, required ferric iron for increased activity, and contained amino acids. Short fiber formation and disruption of filter paper during interaction with these extracts was enhanced by prior acid treatment and eliminated by prior base treatment. The amount of soluble carbohydrate hydrolyzed in 24 h from filter paper by whole cellulase complex was not changed by first disrupting the substrate with the extracts.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260310407
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  • 9
    Electronic Resource
    Electronic Resource
    Polystyrene-polyethylene melt blends obtained through reactive mixing process (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 1634-1641 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Reactive polystyrene (OPS) and reactive polyethylene (CPE) with oxazoline and carboxylic acid functionality, respectively, were melt blended in a Rheomix mixer under a variety of conditions. The properties of these blends were examined and correlated with the compositions and mixing conditions such as shear rate, time, and temperature. An increase in torque was observed, which is believed related to chemical reaction between OPS and CPE. The difference between the maximum and minimum torque (Tmax-Tmin), increases from 48 to a maximum of 510 m-g for 10 and 40% CPE reacted blends, respectively, But on further increase in the CPE amount in the blend the torque increase drops reaching a final minimum value of 133 m-g for a blend with 90% CPE. Differential Scanning Calorimetry (DSC) studies reveal a single first order transition, due to CPE, for each of these polymer blends. Furthermore, evidence of the glass transition temperature for OPS diminishes with increasing CPE content and mixing time. Scanning Electron Micrographs (SEM) show a fine dispersion in these reactive blends, with particle size much smaller than a micron. Blends with 50% or more CPE have no distinguishable features as such. Mechanical properties such as elongation at break of reacted blends are improved over the nonreactive polyethylene (PE) and polystyrene (PS) blends. An intermolecular reaction between the OPS and CPE results in a graft polymer, which imparts improvement in the overall properties of these reacted blends. The maximum grafting reaction corresponds to 40% CPE blend, which is being evaluated as a potential compatibilizer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760272110
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  • 10
    Electronic Resource
    Electronic Resource
    Rubber toughening of polystyrene through reactive blending (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1427-1433 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Acrylonitrile-butadiene rubber having carboxylic acid groups (XNBR) and polystyrene having oxazoline groups, were melt blended in a Rheomix mixer under optimized conditions, The ratio of rubber to polystyrene phase was kept constant at 1:4 by weight. The concentration of the reactive oxazoline groups in the polystyrene phase was varied by mixing polystyrene (PS) with a copolymer of styrene and vinyl oxazoline (OPS). A torque rise observed during blending was found to be related to the concentration of oxazoline-carboxylic acid pairs. This torque rise, and independently measured increases in viscosity, both indicate inter-polymer crosslinkihg. Scanning electron microscopy was used to observe the morphology of the blends. Improved rubber phase dispersion was observed with increasing oxazoline concentration. Instrumented impact strength measurements were made using an unnotched Charpy technique. The plastic yielding was then quantified with the use of a ductility ratio. The impact strengths and ductility of the reactive blends are found to be up to 73% greater than those of the corresponding non-reactive blends. Increasing the OPS concentration beyond 5% results in decreasing impact strength, for as the compatibility increases, the rubber particle size decreases below an effective size for rubber toughening. Similar impact improvement is observed when the major PS phase is substituted with high impact polystyrene (HIPS) containing some OPS.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760282112
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