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  • 1
    ISSN: 1573-1561
    Keywords: Cinnamic acids ; bird repellents ; quantitative structure–activity relationship ; dose–response ; pigeon ; Columba livia ; crop protection ; feeding deterrent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Plants have evolved an array of defense chemicals that inhibit the feeding of vertebrate herbivores and therefore have potential for agricultural and environmental applications to reduce feeding damage. We investigated the relationship between structure and repellency for 14 derivatives of the plant secondary compound, cinnamic acid, using the feral pigeon (Columba livia) as the test species. The mechanism behind the repellent activity of these derivatives is explained by a combination of four descriptors: heat of formation (ΔH f), polarizability (XY and YY) and superdelocalizability (Sr). All these parameters are electronic, indicating that changes in electronic distribution within cinnamic acid structures are crucial for activity. This is the first published quantitative structure–activity model for avian repellents, and as a result we can now begin to predict which cinnamic acid derivatives should make effective repellents. The full power of this model to aid the selection and screening of new repellents awaits further experimentation on both related compounds and other avian species. However, this modeling approach promises to provide a more efficient and economic method for prospecting chemical databases for new effective bird repellents.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9680
    Keywords: Agroforestry ; herbicide ; nitrate ; nutrition ; leaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Concentrations of nitrate have been measured in soil water samples collected during the first year of an agroforestry trial at an upland site in Wales. Nitrate concentrations were higher in water samples collected from herbicide-treated areas around trees than from undisturbed pasture between the trees. These differences were statistically significant fo samples collected during the summer but not for those from the main winter leaching period. The enhanced nitrate concentrations that were measured beneath the tree planting positions may have implications for the nutrition of the trees but, at the planting densities included in the trial (100 and 400 trees/ha), are estimated to represent only a small increase in the nitrate content of water draining from the agroforestry area as a whole, relative to that from unplanted pasture. There was some evidence that preferential deposition of urine, but not of dung, contributed to the increased nitrate contents in the soil around the planting positions.
    Type of Medium: Electronic Resource
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