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  • 1
    Electronic Resource
    Electronic Resource
    Flavonoids as plant signals to rhizosphere microbes (1992)
    Springer
    Mycorrhiza 1 (1992), S. 55-58 
    Details
    ISSN: 1432-1890
    Keywords: Glomus ; Nodulation ; Rhizobium ; Spore germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Certain flavonoids released from plants regulate activities of soil microbes at micromolar and nanomolar concentrations. Processes affected by these compounds include induction of nodulation gene transcription in rhizobial bacteria, promotion of chemotaxis in rhizobia, increase in growth rate of several bacterial species, and enhancement of Glomus spore germination and hyphal growth. Data on the amount and identity of flavonoids released from several crop plant species form a new basis for molecular genetic and ecological studies of the rhizosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206136
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  • 2
    Electronic Resource
    Electronic Resource
    Patch size of forest openings and arthropod populations (1991)
    Springer
    Oecologia 86 (1991), S. 325-334 
    Details
    ISSN: 1432-1939
    Keywords: Arthropods ; Disturbance ; Patch dynamics ; Southern Appalachian Mountains ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five sizes of canopy openings (0.016 ha to 10 ha) were established in the Southern Appalachian Mountains in early 1982 to examine the initial patterns of plant and arthropod establishment across a size range of forest disturbances. Vegetation standing crop after the first growing season was considerably higher in large than small openings in apparent response to greater resource release (e.g., sunlight) in larger openings. Woody stump and root sprouts were the dominant mode of revegetation in each patch size. Forest dominants such as Quercus rubra, Q. prinus and Carya spp. were less important as sprouters in openings than several minor forest components (e.g., Robinia pseudo-acacia, Acer rubrum, Halesia carolina and Cornus florida). Arthropod abundance and community composition varied across the size range of forest openings. Arthropods from the surrounding forest readily utilized the smallest canopy openings (0.016 ha). All feeding guilds were well represented in these small openings and herbivore biomass and load (mg of herbivores/g of foliage) were much higher than in larger patches. In contrast, arthropod abundance and species richness were significantly lower in mid-size than smaller patches. The relatively sparse cover and high sunlight in mid-size openings may have promoted surface heat buildups or soil surface/litter moisture deficits which restricted arthropod entry from the surrounding forest. Arthropod abundance and species richness were higher in large than mid-size patches. The greater vegetation cover in larger openings may have minimized the deleterious effects on arthropod populations. However, the absence of population increases among these arthropod species maintained herbivore loads at very low levels in large patches. Our results suggest that arthropod abundance and diversity in sprout-dominated forest openings are highly dependent on the extent of environmental differences between patch and surrounding forest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317597
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  • 3
    Electronic Resource
    Electronic Resource
    Host-feeding and egg maturation byPachycrepoideus vindemiae (1993)
    Springer
    Entomologia experimentalis et applicata 69 (1993), S. 75-82 
    Details
    ISSN: 1570-7458
    Keywords: host feeding ; preference ; Pachycrepoideus vindemiae ; parasitoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pachycrepoideus vindemiae Rondani (Hymenoptera: Pteromalidae) is a facultative hyperparasitoid ofDrosophila parasitoids in Europe. FemaleP. vindemiae host-feed from the same hosts into which they lay eggs and this enables them to mature additional eggs.P. vindemiae females were allowed to host-feed from puparia containingDrosophila melanogaster Meigen (Diptera: Drosophilidae) pupae or pupae ofAsobara tabida Nees (Hymenoptera: Braconidae). Wasps which had host-fed carried significantly more eggs; the species of host which was fed from had no significant effect on the number of mature eggs in the ovaries. Host-feeding caused no significant reduction in the size of the emerging offspring.P. vindemiae were allowed to forage over patches containing different frequencies of the two host species. No significant oviposition preference was found but there were marked host-feeding preferences which were affected by the age of the host pupae. It is suggested that these preferences were due to the physical nature of the hosts which were fed from.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02380676
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructure of the digestive system of the cercaria of Sanguinicola inermis Plehn, 1905 (Digenea: Sanguinicolidae) (1994)
    Springer
    Systematic parasitology 29 (1994), S. 1-12 
    Details
    ISSN: 1573-5192
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The digenean blood fluke Sanguinicola inermis and the family Sanguinicolidae have previously been described as apharyngeate and sucker-less. Examination of the digestive tract of the cercaria of S. inermis with transmission electron microscopy (TEM), however, has confirmed the presence of a well-developed and complex muscular region immediately adjacent to the sub-terminal mouth. The presence of this muscular region, which may be an oral sucker, emphasises the need for further ultrastructural studies on other members of the family. The adjacent oesophagus, composed of modified tegument, has distinct anterior and posterior regions. TEM shows that the surface of the posterior oesophagus is deeply folded and the apical cytoplasm and sunken cytons become filled with secretory granules, eventually forming a “secretory region” adjacent to the intestine. The dorsal, sac-like intestine is composed of a single layer of epithelial cells, the apical surface of which is drawn into shallow folds. Each cell contains numerous secretory granules, rough ER, and a single basal nucleus. The intestinal lumen, which contains electrondense striated bodies, is filled with fibrous material. Only two sensory oral papillae are associated with the digestive tract, positioned either side of the mouth opening and possibly acting as tango-, stretch- or pressure receptors. The papillae comprise several microtubules lying beneath the apical cytoplasm of the tegument within a nerve process, but there is no connection with the external body surface. The morphology of the alimentary canal of the S. inermis cercaria is discussed in relation to the functioning of the digestive system in preparation for establishment in the final host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009834
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  • 5
    Electronic Resource
    Electronic Resource
    Germacrone defends labrador tea from browsing by snowshoe hares (1990)
    Springer
    Journal of chemical ecology 16 (1990), S. 1961-1970 
    Details
    ISSN: 1573-1561
    Keywords: Labrador tea ; Ledum groenlandicum ; snowshoe hare ; Lepus americanus ; herbivore ; plant chemical defense ; germacrone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Labrador tea (Ledum groenlandicum), a slow-growing late successional evergreen, is highly unpalatable to snowshoe hares (Lepus americanus). Germacrone, a sesquiterpene that is the major component of the essential oil ofL. groenlandicum, was shown by bioassay to be a potent antifeedant to hares. Its concentrations in leaves and intemodes of the plant are high enough to defendL. groenlandicum from hares. This chemical defense of Labrador tea from herbivory is consistent with the resource availability theory of antiherbivore defense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01020508
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of trends in tillage practices on erosion and carbon content of soils in the US corn belt (1993)
    Springer
    Water, air & soil pollution 70 (1993), S. 389-401 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The EPIC model was used to simulate soil erosion and soil C content at 100 randomly selected sites in the US corn belt. Four management scenarios were run for 100 years: (1) current mix of tillage practices maintained; (2) current trend of conversion to mulch-till and no-till maintained; (3) trend to increased no-till; (4) trend to increased no-till with addition of winter wheat cover crop. As expected, the three alternative scenarios resulted in substantial decreases in soil erosion compared to the current mix of tillage practices. C content of the top 15 cm of soil increased for the alternative scenarios, while remaining approximately constant for the current tillage mix. However, total soil C to a depth of 1 m from the original surface decreased for all scenarios except for the no-till plus winter wheat cover crop scenario. Extrapolated to the entire US corn belt, the model results suggest that, under the current mix of tillage practices, soils used for corn and/or soybean production will lose 3.2 × 106 tons of C per year for the next 100 years. About 21% of this loss will be C transported off-site by soil erosion; an unknown fraction of this C will be released to the atmosphere. For the base trend and increased no-till trend, these soils are projected to lose 2.2 × 106 t-C yr−1 and 1.0 × 106 t-C yr−1, respectively. Under the increased no-till plus cover crop scenario, these soils become a small sink of 0.1 × 106 t-C yr−1. Thus, a shift from current tillage practices to widespread use of no-till plus winter cover could conserve and sequester a total of 3.3 × 106 t-C yr−1 in the soil for the next 100 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01105010
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  • 7
    Electronic Resource
    Electronic Resource
    A single trapped antiproton and antiprotons for antihydrogen production (1993)
    Springer
    Hyperfine interactions 81 (1993), S. 5-14 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the last several years, our TRAP collaboration has pioneered techniques for slowing, trapping, cooling and indefinitely storing antiprotons to energies more than 1010 times lower than previously possible. The radio signal from a single trapped antiproton is now being used for precision measurements. Many cold antiprotons are “stacked” as another important step toward the eventual production of antihydrogen, and positrons have been trapped in vacuum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567246
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  • 8
    Electronic Resource
    Electronic Resource
    Extremely cold antiprotons for antihydrogen production (1993)
    Springer
    Hyperfine interactions 76 (1993), S. 81-93 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The possibility to produce, trap and study antihydrogen atoms rests upon the recent availability of extremely cold antiprotons in a Penning trap. Over the last five years, our TRAP Collaboration has slowed, cooled and stored antiprotons at energies 1010 lower than was previously possible. The storage time exceeds 3.4 months despite the extremely low energy, which corresponds to 4.2 K in temperature units. The first example of measurements which become possible with extremely cold antiprotons is a comparison of the antiproton inertial masses which shows they are the same to a fractional accuracy of 4×10−8. (This is 1000 times more accurate than previous comparisons and large additional increases in accuracy are anticipated.) To increase the number of trapped antiprotons available for antihydrogen production, we have demonstrated that we can accumulate or “stack” antiprotons cooled from successive pulsed injections into our trap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02316708
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis, release, and transmission of alfalfa signals to rhizobial symbionts (1994)
    Springer
    Plant and soil 161 (1994), S. 69-80 
    Details
    ISSN: 1573-5036
    Keywords: betaines ; flavonoids ; Medicago sativa ; nodulation ; Rhizobium meliloti
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In addition to the flavonoids exuded by many legumes as signals to their rhizobial symbionts, alfalfa (Medicago sativa L.) releases two betaines, trigonelline and stachydrine, that induce nodulation (nod) genes inRhizobium meliloti. Experiments with14C-phenylalanine in the presence and absence of phenylalanine ammonia-lyase inhibitors show that exudation of flavonoidnod-gene inducers from alfalfa roots is linked closely to their concurrent synthesis. In contrast, flavonoid and betainenod-gene inducers are already present on mature seeds before they are released during germination. Alfalfa seeds and roots release structurally differentnod-gene-inducing signals in the absence of rhizobia. WhenR. meliloti is added to roots, medicarpin, a classical isoflavonoid phytoalexin normally elicited by pathogens, and anod-gene-inducing compound, formononetin-7-O-(6″-O-malonylglycoside), are exuded. Carbon flow through the phenylpropanoid pathway and into the flavonoid pathway via chalcone synthase is controlled by complexcis-acting sequences andtrans-acting factors which are not completely understood. Even less information is available on molecular regulation of the two other biosynthetic pathways that produce trigonelline and stachydrine. Presumably the three separate pathways for producingnod-gene inducers in some way protect the plant against fluctuations in the production or transmission of the two classes of signals. Factors influencing transmission of alfalfanod-gene inducers through soil are poorly defined, but solubility differences between hydrophobic flavonoids and hydrophilic betaines suggest that the diffusional traits of these molecules are not similar. Knowledge derived from studies of how legumes regulate rhizobial symbionts with natural plant products offers a basis for defining new fundamental concepts of rhizosphere ecology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02183086
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  • 10
    Electronic Resource
    Electronic Resource
    Evolution of the weld heat-affected zone microstructure in a Ti-48AI-2Cr-2Nb gamma titanium aluminide (1994)
    Springer
    Journal of materials science 13 (1994), S. 1061-1065 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277040
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