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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 467-469 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A system for storage and continuous dispensing of constant activity 11CO2 from batch production is described. The system has been used successfully to maintain constant activity levels for 2-h plant tracer kinetic experiments. This development now allows any existing cyclotron facility to supply a radioisotope stream continuously from a short batch irradiation. It requires no modification for use with other isotopes such as N-13 or O-15 in gaseous form and can be used in other biological and clinical investigations as well as the plant physiology investigations for which it was developed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Steady-state labelling with 11CO2 was used to observe the blocking of phloem transport, induced by chilling short regions of stems or petioles of velvetleaf (Abutilon theophrasti Medic.) or cotton (Gossipium hirsutum L.). The abruptness of these blockages was evidenced by sharp decreases in 11C activity below, and increases above a 2 to 3 cm region cooled from 28°C to 18 or 13°C for periods as short as 2 min. Abrupt unblocking of transport in velvetleaf occurred a few minutes after rewarming, as evidenced by a sharp rise and and overshoot in 11C activity. Recovery of transport in cotton was more prolonged and was marked by occasional spontaneous blocking and unblocking of transport at various points along the petiole or stem, not necessarily in the cooled region. Similar spontaneous events were often observed in undisturbed cotton plants, but only rarely in velvetleaf.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 72 (1988), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Jaeger, C. H., Goeschl, J. D., Magnuson, C. E., Fares, Y. and Strain, B. R. 1988. Short-term responses of phloem transport to mechanical perturbation. - Physiol. Plant. 72: 588–594.Phloem transport was monitored using a continuous stream of 11CO2-labelled air administered to one leaf while gamma detectors measured 11C activity at intervals along the stem. The effect of gentle, non-injurious mechanical perturbation on phloem transport was tested in cotton (Gossypium hirsutum L. cv. Stoneville 213). Mechanical stimuli such as shaking, localized vibration and gentle massage were applied while the plants were at isotope equilibrium. Localized phloem blockages were observed within 1–2 min of the stimuli. The blockages lasted from 6–55 min and full recovery of transport required 20–175 min. The effect of preconditioning to mechanical perturbation on phloem transport was tested in bush beans (Phaseolus vulgaris L. cv. Cherokee Bush). Preconditioning of a bean seedling to gentle stem massage resulted in a shorter blockage response and quicker transport recovery period when the seedling was massaged during a 11C tracer experiment compared to a control seedling. These results indicate that measurements of phloem transport on recently disturbed plants will probably show depressed phloem transport velocities. Measurements should be made after at least a 24-h disturbance-free recovery period.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary An integrated approach to study the effects of environmental factors on plants is described. The central theme of the system is the use of CO2 labelled with11C supplied continuously to the plant and following the emitted radiation in vivo in the leaf, the phloem and the various sinks. The system consists of six components and with minor changes can be used for other tracers such as13N for nitrogen fixation studies. Because of the short half life of the isotope, several experiments can be carried out on the same plant under the same environmental conditions without disturbing the plant. A host of ecologically, agriculturally and genetically important questions can be answered using this technique.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-515X
    Keywords: alpine tundra ; methane ; trace gas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured CH4 fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH4 flux during the snow-free season corresponded roughly with these plant communities. InCarex-dominated meadows, which receive the most moisture from snowmelt, net CH4 production occurred. However, CH4 production in oneCarex site (seasonal mean=+8.45 mg CH4 m−2 d−1) was significantly larger than in the otherCarex sites (seasonal means=−0.06 and +0.05 mg CH4 m−2 d−1). This high CH4 flux may have resulted from shallower snowpack during the winter. InAcomastylis meadows, which have an intermediate moisture regime, CH4 oxidation dominated (seasonal mean=−0.43 mg CH4 m−2 d−1). In the windsweptKobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH4 oxidation was observed (seasonal mean=−0.77 mg CH4 m−2 d−1). Methane fluxes correlated with a different set of environmental factors within each plant community. In theCarex plant community, CH4 emission was limited by soil temperature. In theAcomastylis meadows, CH4 oxidation rates correlated positively with soil temperature and negatively with soil moisture. In theKobresia community, CH4 oxidation was stimulated by precipitation. Thus, both snow-free season CH4 fluxes and the controls on those CH4 fluxes were related to the plant communities determined by winter snowpack.
    Type of Medium: Electronic Resource
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