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  • Analytical Chemistry and Spectroscopy  (10)
  • sorghum  (4)
  • Allelopathy  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 10 (1984), S. 161-170 
    ISSN: 1573-1561
    Keywords: Ferulic acid ; allelopathy ; temperature stress ; sorghum ; soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Experiments were conducted to test the hypothesis that alleiopathic effects of ferulic acid (FA) may be altered by the temperature conditions of the growth environment. Growth of grain sorghum and soybean seedlings over a 10-day treatment period showed that a significant interaction effect occurred between environmental temperatures and FA treatments. Sorghum grown with an average day temperature of 37 °C and soybeans grown at 34 °C had greater dry weight reductions caused by FA than when the respective environments were 8 °C and 11 °C lower. The threshold concentration for inhibition of sorghum growth was 0.2 mM FA under the hot conditions and 0.4 mM FA with the cooler conditions. Soybeans were more sensitive than sorghum, and these inhibition thresholds for the hot and cool environments were 0.1 and 0.25 mM FA. These results demonstrate that temperature stress enhances allelochemical inhibition and indicate that interactions with the environment are an important consideration for understanding allelopathy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 15 (1989), S. 951-960 
    ISSN: 1573-1561
    Keywords: Allelopathy ; grain sorghum ; Sorghum bicolor ; weed inhibition ; weed management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three years of field data in northeastern Nebraska demonstrate that a grain sorghum crop reduces weediness in the following crop year. Weed growth was consistently lower in sorghum areas the year after strip-cropping fields with sequences of four-row bands of grain sorghum, soybeans, and corn. Percentage weed cover was significantly lower early in the year, and midsummer weed biomass was well below that found after corn and soybeans. Weed biomass in June and July following corn was two to four times that of grain sorghum strips. Inhibitory effects of grain sorghum were primarily on broadleaf weeds, often showing no action on grass weeds. No obvious differences were noted in the weed species present after the three crops. Allelopathy provides a logical explanation for the sorghum-mediated weed inhibition found in this study. The data have implications for weed management strategies in agriculture.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 5 (1979), S. 815-824 
    ISSN: 1573-1561
    Keywords: Ferulic acid ; p-coumaric acid ; vanillic acid ; chlorophyll a ; chlorophyll b ; allelopathy ; inhibitors ; soybean ; sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Experiments were designed to test the hypothesis that interference with chlorophyll metabolism may be one mechanism of inhibition of plant growth in allelopathic interactions. Effects of ferulic,p-coumaric, and vanillic acids on soybean and grain sorghum growth and chlorophyll content were quantified and compared after seedlings were treated with these compounds in a nutrient culture. Following a 6-day treatment cycle, dry weights of soybean seedlings were reduced by both 10−3 M and 5 × 10−4 M treatments of ferulic,p-coumaric and vanillic acids. Soybean weight reductions in each case were paralleled by a significant reduction in the concentration (μg Chl/mg dry wt) of chlorophylls a and b and total chlorophyll in the unifoliate leaves. Sorghum seedling growth was also reduced by each of the compounds at the 5 × 10−4 M level, but leaf chlorophyll concentration was not below that of control plants.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 3 (1977), S. 197-205 
    ISSN: 1573-1561
    Keywords: synergism ; ferulic acid ; p-coumaric acid ; allelopathy ; phytotoxicity ; inhibition ; sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The data support the hypothesis that there is a synergistic phytotoxic effect whenp-coumaric and ferulic acids are found together. Equimolar mixtures of both acids showed greater reduction in sorghum seed germination, shoot elongation, and total seedling growth than either phytotoxin caused when alone. Repeated experiments showed mixtures containing 5×10−3 Mp-coumaric and 5×10−3 M ferulic acids reduced germination to 34% of controls after 24 hr and 59% by 48 hr. The same concentration of either phenol-treated seeds alone showed 69 and 92% germination at comparable times. The phytotoxic action of the combination approximated the inhibitory effect on germination of 10−2 M ferulic acid and was a greater reduction than caused by 10−2 Mp-coumaric treatments. Sorghum seedling growth was more sensitive than germination, with an equimolar mixture of 2.5×10−4 Mp-coumaric and 2.5×10−4 M ferulic acids reducing seedling dry weight significantly below weights of seedlings treated separately with 2.5×10−4 Mp-coumaric or ferulic acids. Further dilutions showed a 1.25×10−4 M concentration of either phenol was stimulatory to seedling growth, whereas a mixture of these two produced inhibition.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 14 (1988), S. 1821-1828 
    ISSN: 1573-1561
    Keywords: Allelopathy ; bioassay ; mechanism of action ; seed germination ; radicle growth ; seedling growth ; Lemna bioassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The bioassay has been one of the most widely used tests to demonstrate allelopathic activity. Often, claims that a particular plant species inhibits the growth of another are based entirely on the seed germination response to solvent extracts of the suspected allelopathic plant; few of these tests are of value in demonstrating allelopathy under natural conditions. The veracity of the bioassay for evaluating naturally occurring compounds for phytotoxicity depends upon the physiological and biochemical response capacity of the bioassay organism and the mechanism(s) of action of the allelochemicals. The possibility that more than one allelochemical, acting in concert at very low concentrations, may be responsible for an observed allelopathic effect makes it imperative that bioassays be extremely sensitive to chemical growth perturbation agents. Among the many measures of phytotoxicity of allelochemicals, the inhibition (or stimulation) of seed germination, radicle elongation, and/or seedling growth have been the parameters of choice for most investigations. Few of these assays have been selected with the view towards the possible mechanism of the allelopathic effect.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 4 (1978), S. 425-436 
    ISSN: 1573-1561
    Keywords: synergism ; vanillic acid ; p-hydroxybenzoic acid ; allelopathy ; inhibition ; sorghum ; radish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Radish and grain sorghum germination and sorghum growth were inhibited in a synergistic manner by combinations of vanillic andp-hydroxybenzoic acids. At threshold inhibition levels, 2.5 × 10−3 M vanillic acid-treated radish seeds had 71 % of control germination after 24 hr and 2.5 × 10−3 Mp-hydroxybenzoic acid-treated radish yielded 95% germination. A mixture of 2.5 × 10−3 M of each of these two phytotoxins showed 52% germination after 24 hr. Equimolar mixtures of 5 × 10−3 M vanillic andp-hydroxybenzoic acids allowed sorghum germination of 60% of untreated seeds after 24 hr, whereas separate treatments of individual phenols had 93% and 96% of control seed germination. Sorghum root and shoot elongation and total seedling growth were more sensitive than germination to vanillic andp-hydroxybenzoic acid treatments, and synergistic effects also were apparent. A combination of 5 × 10−3 M vanillic with 5 × 10−3 Mp-hydroxybenzoic reduced root length more than either did individually, and a mixture of 5 × 10−4 M vanillic with 5 × 10−4 Mp-hydroxybenzoic acid reduced sorghum seedling growth to approximately that resulting from a 10−3 M concentration of either phenol alone. Phytotoxin levels inhibitory to sorghum growth caused small increases in lower leaf surface diffusive resistance, but did not close stomates, and this effect was not judged to be the cause of reduced sorghum growth.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 98 (1987), S. 99-109 
    ISSN: 1573-5036
    Keywords: Allelopathy ; Ferulic acid ; Magnesium ; Mineral content ; Phosphorus ; PotassiumSorghum bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two week old sorghum seedlings (Sorghum bicolor L. Moench) were treated with ferulic acid added to the nutrient solution. Effects on tissue concentration of P, K, Mg, Ca, Fe, and Zn were evaluated after 3 and 6 days. Treatemnts of 0.25 mM ferulic acid approximated the growth inhibition threshold, and after 6 days 0.5 mM treated plants weighed less than controls. Both treatments reduced the P content of the roots and shoots at the 3- and 6-day harvests in three replicate experiments. Roots of treated plants at both harvests had a lower concentration of K and Mg. These reductions in P, K, and Mg were most extensive from the 0.5 mM ferulic acid regime. In some cases at both harvests, shoot K was lower and Mg was higher than control tissue. Ferulic acid effects at the 3-day harvest included an elevation of Ca and depression of Fe in shoots. Changes in nutrient content preceded measurable differences in plant weight. These data indicate that one mechanism of growth inhibition by this allelochemical may be an alteration of nutrient balance.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simulation study is described of the behaviour of ions confined in a quadrupole ion trap during each of two separate operations of a tandem mass spectrometric experiment. The two operations are those of mass-selective ion isolation and mass-selective resonance excitation to the point of ion ejection from the ion trap. The method of mass-selective ion isolation simulated is that of consecutive ion isolation. Simulation data indicate that the collisional history of the ions prior to the isolation process can greatly influence the degree to which ions survive this process. Simulation data for mass-selective resonance ejection are compared with experimental data obtained with a Finnigan-MAT ion trap mass spectrometer. In each operation, the facility with which ions absorb energy from the field within the ion trap, whether this field is derived from the R.F. drive potential or a supplementary potential, can determine the extent to which ions are retained within the ion trap during the two mass-selective operations described.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Commercial gas chromatography quadrupole ion-trap mass spectrometer (GC/ITMS) instruments have been used in a novel way for the study of negative ions formed from perfluorotributyl-amine and polychlorinated biphenyl compounds. Negative ions, formed during a normal electron impact ionization period in which 70 eV electrons were used, were isolated in an ion trap by the application of a negative DC voltage to the ring electrode that caused all positive ions to be ejected from the ion trap; in the subsequent analytical scan, negatives ions were detected with an electron multiplier biased normally so as to detect positive ions. The major negative-ion species detected from FC-43 were m/z 252 to m/z 633; 34 other negative-ion species were detected also, though in low abundance. The observed negative-ion mass range extended from m/z 252 to m/z 633. The signal-to-noise ratio of negative-ion mass spectra was enhanced by operation of the GC/MS instrument in GC mode and averaging the mass spectra acquired. In an examination of 3 hexachlorobiphenyl compounds, the molecular anion cluster around m/z 360 for the non-ortho-substituted congener 169 was observed with a signal-to-noise ratio of ca. 20 for 90 pg injected on column: the response for congener 169 was greater than that for congener 156 (mono-ortho-substituted) which, in turn, was greater than that for congener 153 (di-ortho-substituted).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 929-934 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: When the working point of a precursor ion confined within a quadrupole ion trap is moved to the vicinity of a boundary of the stability diagram, fragmentation of the precursor ion can be induced by virtue of energy gained from the radio-frequency trapping field. This behaviour is known as the ‘border effect’. When the isolated precursor ion is subjected to a cooling period of variable duration, in the presence of helium buffer gas and prior to experiencing the ‘border effect’, a high degree of control of the fragmentation pattern is achieved. The cooling period causes decreases in both ion kinetic energy and ion axial excursions. From this preliminary study, it is suggested that the deposition of internal energy during the ‘border effect’ can be varied by changing the duration of the cooling period. In addition to a degree of control of internal energy deposition, the amount of energy which can be deposited in this manner, though unknown, appears to exceed those energy levels achievable with resonance excitation and the ‘border effect’ without collisional cooling, in that an additional fragmentation channel is accessed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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