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  • 1
    Electronic Resource
    Electronic Resource
    Chemical inhibition of fire-prone grasses by fire-sensitive shrub,Conradina canescens (1989)
    Springer
    Journal of chemical ecology 15 (1989), S. 1567-1577 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; fire ; monoterpenes ; trichomes ; Conradina canescens ; Pinus ; Schizachyrium scoparium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In an investigation of potential chemical activity of fire-sensitive shrubs in Florida's sand pine scrub community, bioassays of foliar washes ofConradina canescens showed significant inhibitory activity on three native grasses that are known to fuel frequent surface fires; inhibition was concentrated seasonally in spring and summer. Application of runoff fromConradina leaves to one of the grasses caused a 50% reduction in growth over a 20-week period. Isolation of the biologically active fractions from the fresh leaves ofC. canescens yielded numerous monoterpenes, a number of which were identified from a GC-MS reference library and/or MS comparison to authentic compounds: 11 from the diethyl ether extract, 11 from steam distillation, and four from the foliar leaf wash. Numerous other monoterpenes present in the extractions were unknown. The terpenoid fraction completely inhibited seed germination of one of the native grasses and of lettuce. Saturated aqueous solutions of nine of the monoterpenes inhibited germination and radicle growth of two native grasses. SEM views of the leaf surfaces ofConradina reveal secretory trichomes that appear to be the source of the monoterpenes as well as the triterpene, ursolic acid. The biological activity ofC. canescens as a fire-sensitive component of the scrub community is reviewed in light of the chemical evidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01012384
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  • 2
    Electronic Resource
    Electronic Resource
    In search of allelopathy in the Florida scrub: The role of terpenoids (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 1355-1380 
    Details
    ISSN: 1573-1561
    Keywords: Calamintha ashei (Labiatae) ; Conradina canescens (Labiatae) ; Chrysoma pauciflosculosa (Asteraceae) ; Ceratiola ericiodes (Empetraceae) ; terpenoids ; allelopathy ; mechanisms of release ; water transport ; activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The hypothesis was tested that allelopathic agents released from fire-sensitive plants of the Florida scrub community deter the invasion of fireprone sandhill grasses. The structures of the constituents of four endemic scrub species,Conradina canescens, Calamintha ashei, Chrysoma pauciflosculosa, andCeratiola ericiodes, were established and their phytotoxic activity against two grasses of the sandhill was examined. Effects of the secondary metabolites from the above scrub species and their degradation products upon the germination and radicle growth of little bluestem (Schizachyrium scoparium) and green sprangletop (Leptochloa dubia), two native grasses of the Florida sandhill community, were determined. The studies included determination of the water solubility and release mechanism of terpenes and other allelopathic agents from the source plants and their aqueous transport to the target species. Some of the natural products were nontoxic until activated by light and/or oxidation after release from the source plant into the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02059812
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  • 3
    Electronic Resource
    Electronic Resource
    Inhibition and promotion of germination by several sesquiterpenes (1989)
    Springer
    Journal of chemical ecology 15 (1989), S. 1785-1793 
    Details
    ISSN: 1573-1561
    Keywords: Burrodin ; confertiflorin ; desacetylconfertiflorin ; dihydroparthenolide ; parthenin ; 7α-hydroxy-3-desoxyzaluzanin C ; guayulin A ; sesquiterpene lactone ; allelopathy ; seed germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The sesquiterpene lactones, burrodin, confertiflorin. desacetyl-confertiflorin, dihydroparthenolide, parthenin, and 7α-hydroxy-3-desoxyzaluzanin C, and the sesquiterpene ester guayulin A were assayed at concentrations of 1, 10, and 100 μM for effects on seed germination of 16 dicot and nine monocot species. Six of the dicot and two of the monocot species were affected by one or more of these compounds. Germination was both inhibited and promoted, depending on the compound and the specific species or cultivars, at concentrations as low as 1 μM. For example, guayulin A, which promoted the germination of lettuce at all concentrations tested, inhibited the germination of tomato. Confertiflorin stimulated germination of the lettuce cultivar Grand Rapids at 1 μM, but inhibited germination of a light-sensitive cultivar at all concentrations tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01012266
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  • 4
    Electronic Resource
    Electronic Resource
    Allelopathic potential of menthofuran monoterpenes fromCalamintha ashei (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 3345-3359 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; Calamintha ashei ; Florida Scrub ; menthofurans ; monoterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A reversed-phase HPLC analysis was used to separate and quantify five menthofuran monoterpenes inCalamintha ashei leaf soaks and washes. (+)-Evodone and desacetylcalaminthone were the major constituents of both soaks and washes. Concentrations of (+)-evodone and desacetylcalaminthone were as high as 0.66 and 0.74 mM, respectively, in leaf soaks. The highest concentration of monoterpenes in leaf washes obtained by misting was 0.021 mM. Aqueous solubilities of the menthofurans were determined to exceed concentrations required for growth inhibition. Bioassays of individualCalamintha monoterpenes demonstrated effects on germination as low as 0.05 mM for (+)-evodone. An equimolar mixture of desacetylcalaminthone and (+)-evodone reducedRudbeckia hirta germination by 17% at a combined concentration of 0.025 mM forLeptochloa dubia. Confirmation of allelopathic effects byCalamintha ashei will require long-term bioassays ofCalamintha menthofurans on the growth of native sandhill species under conditions comparable to the harsh environment of the Florida scrub.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02033731
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  • 5
    Electronic Resource
    Electronic Resource
    Just how insoluble are monoterpenes? (1993)
    Springer
    Journal of chemical ecology 19 (1993), S. 1799-1807 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; monoterpenes ; Calamintha ashei ; Conradina canescens ; ursolic acid ; borneol ; camphor ; juglone ; solubility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Prior generalizations about the ecological roles of monoterpenes may be misleading if based on the presumed insolubility of monoterpenes in water. We determined the aqueous solubility of 31 biologically active monoterpenes by gas chromatography. While hydrocarbons were of low solubility (〈 35 ppm), oxygenated monoterpenes exhibited solubilities one or two orders of magnitude higher, with ranges of 155–6990 ppm for ketones and of 183–1360 ppm for alcohols. Many monoterpenes are phytotoxic in concentrations under 100 ppm, well below the saturated aqueous concentrations of oxygenated monoterpenes. Therefore, even dilute, unsaturated solutions of monoterpenes, occurring naturally in plant tissues and soil solutions, may act as potent biological inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00982309
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