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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 42 (1991), S. 77-101 
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The interacting effects of temperature and pH on the kinetics of glutathione reductase from maize have been studied in detail. The apparent Km for oxidized glutathione (GSSG) measured with desalted crude extracts increased in an exponential manner with rising temperature as a single variable. Increasing pH as a single variable also resulted in higher values of apparent Km for GSSG. When pH was allowed to vary with temperature, a curve which combined the pH and temperature responses was observed. Temperature had the stronger influence and this combined curve was displaced from the temperature curve due to the effect of pH. The pH to which the assay buffer was adjusted at 30°C had an influence on the pattern of the results in this type of experiment. The response of apparent Km for NADPH, and of apparent Km for GSSG using partially-purified extracts, were also examined. The variation with temperature, at constant pH, was again exponential. The pattern of change of apparent Km with temperature is strongly dependent on experimental conditions. Affinity/temperature relationships deduced from such data would only reflect enzyme function in vivo if the physiological environment could be reproduced exactly in the assay mixture.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Structural and physiological aspects of the parenchymatous bundle sheath (PBS) were studied in cultivars of Hordeum distichum L. The PBS of intermediate, lateral and midrib veins consisted of a single layer of cells closely appressed to the mestome sheath. These cells were large, vacuolate and approximately cylindrical in shape, extending parallel to the vein. Mean PBS cell volume was 4 × 10−5mm3 compared to 1.23 × 10−5mm3 for mesophyll cells. Transverse sections revealed three cell types within the PBS, cells with small chloroplasts (S-type), cells with large chloroplasts (L-type) and structural cells. The majority of cells were S-type, containing chloroplasts of approximately a third of the volume of mesophyll chloroplasts; they were able to reduce tetranitro blue-tetrazolium and synthesize starch. Structural cells interrupted the phloem and xylem are of the sheath in lateral veins and the midrib, whilst between one and four PBS cells within the phloem are of each vein type contained chloroplasts similar in volume and starch content to those of the mesophyll. Only these L-type cells contained noticeable starch grains at the end of an 8-h dark period, a further 4 h darkness being required for complete mobilization of starch. Starch deposition within S-type and structural cells was detectable after 4 h illumination but was only appreciable in leaves excised from the plant and illuminated for 9–12 h. The role of S-type PBS cells in assimilate transport is discussed in relation to these findings.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 51 (1996), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The use of manipulative experiments to study directly the effects of climate change on natural and managed systems is expensive if performed on a large scale: it also relies upon accurate predictions of future climatic conditions. Predictive modelling is less expensive and permits a range of scenarios to be considered but this is only as reliable as the underpinning model.Predicting the suitability of England and Wales for the cultivation of forage maize under climate change was attempted using an established crop growth model by Muchow et al. (1990) integrated with climate data. The biological and climatic inputs to the model were the thermal requirements for the stages of crop growth, leaf number, leaf area, harvest index, the daily maximum and minimum air temperature, precipitation and solar radiation. These values were obtained from a daily meteorological database for ninety-three sites in England and Wales for the period 1951–80. Model outputs as point values of potential crop yield predicting current production -‘baseline’- were statistically validated using actual crop yield data collated from bibliographic analysis. The baseline results indicated that pans of the south-east appeared to be too dry and the north too cold. The model was run again using an artificial sensitivity test (temperature +2°C. precipitation ±10%). Increased precipitation led to a predicted increase in geographical suitability of the UK for forage maize production to the north and west. Under reduced precipitation there was a decrease in suitability in the south-east, possibly owing to moisture stress.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell reports 6 (1987), S. 435-438 
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The production of carbohydrates by cell suspension cultures of Phleum pratense (timothy grass) is described. Extracellular polysaccharides similar in monosaccharide composition to native cell wall polymers were accumulated, together with polymers of fructose (fructans). The fructans had similar properties to the intracellular reserve polymers found in intact plants, and were found in both cells and media of young, slow-growing cultures. Production of extracellular polysaccharides differed in cultures grown on sucrose or equimolar glucose/fructose as carbon source. These differences were observed only when autoclaved media were used, and were not related to changes in either pH or osmolarity. Autoclaving medium containing radioactive glucose and fructose produced a novel, unidentified labelled compound which was absent in medium containing labelled sucrose.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2048
    Keywords: Displacement transducer (temperatureprofiles, output interpretation) ; Growth ; Lolium (growth, temperature) ; Temperature and growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A device is described for measuring linear extension of grass leaves during controlled cooling and heating of the growing region. The instrument was employed to investigate the sensitivity to temperature of the expanding third and fourth leaves of Lolium temulentum L. seedlings. Using a stepped temperature profile it was established that there was no lag in the response of growth rate to rapid changes in temperature below 16°C. If cooling was continued to the point where growth ceased (1°C) but no further, then rates of growth on rewarming were enhanced over the chilling range and reverted to the original rate at 20°C. Cooling to successively lower subzero temperatures before rewarming abolished the hysteretic enhancement, progressively raised the temperature at which growth resumed and decreased the rate of extension until, at-5.3°C, no recovery occurred. The temperature sensitivity of growth, measured as Q10, was essentially constant when cooling from 20°C to 5°C, with 5°C-grown leaf tissue exhibiting a higher mean Q10 than tissue developed at 20°C. The possible physiological significance of these data is discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Planta 133 (1977), S. 197-200 
    ISSN: 1432-2048
    Keywords: Invertase ; leaf development ; Lolium ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The levels of invertase (E.C. 3.2.1.26) activity were measured throughout the development of the fourth leaf of Lolium temulentum. No neutral invertase activity was detected. Soluble acid invertase activity fell during leaf extension but rose again after ligule formation. This rise continued into senescence and was accompanied by the appearance of activity in the insoluble fraction. Evidence is presented that the insoluble activity was not an artefact of preparation, and that it represented an extracellular acid invertase. Fractionation of soluble invertase by gel filtration showed the appearance of a high molecular weight form at the time when insoluble activity was rising. The relationships between the different forms of the enzyme are discussed, together with their roles in leaf development.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Planta 122 (1975), S. 105-107 
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Callus cultures derived from tubers of Solanum tuberosum L. cv. “Record” were transferred from a complete medium to a maintenance medium that lacked sugar and were then incubated at 2° or 25°. Incubation at 2° for 5 days led to an accumulation of sucrose. This accumulation did not occur at the expense of stored reducing sugars and was not found at 25°. Such cultures could be used for the study of cold-induced sweetening in potatoes.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Thermal Ion Dynamics Experiment (TIDE) and the Plasma Source Instrument (PSI) have been developed in response to the requirements of the ISTP Program for three-dimensional (3D) plasma composition measurements capable of tracking the circulation of low-energy (0–500 eV) plasma through the polar magnetosphere. This plasma is composed of penetrating magnetosheath and escaping ionospheric components. It is in part lost to the downstream solar wind and in part recirculated within the magnetosphere, participating in the formation of the diamagnetic hot plasma sheet and ring current plasma populations. Significant obstacles which have previously made this task impossible include the low density and energy of the outflowing ionospheric plasma plume and the positive spacecraft floating potentials which exclude the lowest-energy plasma from detection on ordinary spacecraft. Based on a unique combination of focusing electrostatic ion optics and time of flight detection and mass analysis, TIDE provides the sensitivity (seven apertures of ∼ 1 cm2 effective area each) and angular resolution (6°×18°) required for this purpose. PSI produces a low energy plasma locally at the POLAR spacecraft that provides the ion current required to balance the photoelectron current, along with a low temperature electron population, regulating the spacecraft potential slightly positive relative to the space plasma. TIDE/PSI will: (a) measure the density and flow fields of the solar and terrestrial plasmas within the high polar cap and magnetospheric lobes; (b) quantify the extent to which ionospheric and solar ions are recirculated within the distant magnetotail neutral sheet or lost to the distant tail and solar wind; (c) investigate the mass-dependent degree energization of these plasmas by measuring their thermodynamic properties; (d) investigate the relative roles of ionosphere and solar wind as sources of plasma to the plasma sheet and ring current.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 1997-11-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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