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  • Carbon/nutrient balance  (1)
  • Induced defense  (1)
  • Labrador tea  (1)
  • 1
    ISSN: 1432-1939
    Keywords: Tissue wounding ; Induced defense ; Secondary phenolics ; Willows ; Salicaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the effects of natural wounding by insects and artificial wounding by clipping with scissors on the phenolic chemistry of two willows, Salix myrsinifolia and Salix pentandra. Half of the blade of a mature leaf was removed from each experimental plant either by allowing insects (chrysomellid beetles) to feed on the leaf or by clipping off half the blade of a leaf with scissors. We also examined the ability of wounded plants to warn neighboring plants of imminent wounding by an airborne signal by maintainign one set of control plants in the room containing the wounded plants and another set of control plants in a room hermetically sealed from the room containing the wounded plants. After 48 h, the experimental leaf and the fourth leaf and eighth leaf upwards in the leaf sequence from the experimental leaf were analyzed for phenols by high-pressure liquid chromatography. The same leaves in the leaf sequence from each control plant were similarly analyzed for phenols. Only one phenol, salicortin in leaves of S. myrsinifolia, increased in concentration in response to defoliation, and the observed response was small. The type of wounding affected this increase in salicortin, with natural wounding by insects causing a greater response than artificial wounding in one S. myrsinifolia clone, and artificial wounding causing a greater response than insect wounding in the other clone. This result indicates that S. myrsinifolia cannot control the effects of diffeeent types of wounding on its leaf secondary chemistry. We also found no indication of airborne warning signals between wounded and unwounded plants that trigger an elevation of leaf defenses in unwounded plants in anticipation of herbivore attack.
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  • 2
    ISSN: 1432-1939
    Keywords: Populus tremuloides ; Carbon/nutrient balance ; Choristoneura conflictana ; Plant/herbivore interaction ; Secondary metabolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated the effects of nitrogen fertilization upon the concentrations of nitrogen, condensed tannin and phenolic glycosides of young quaking aspen (Populus tremuloides) leaves and the quality of these leaves as food for larvae of the large aspen tortrix (Choristoneura conflictana), a Lepidopteran that periodically defoliates quaking aspen growing in North America. Nitrogen fertilization resulted in decreased concentrations of condensed tannin and phenolic glycosides in aspen leaves and an increase in their nitrogen concentration and value as food for the large aspen tortrix. These results indicate that plant carbon/nutrient balance influences the quality of aspen leaves as food for the large aspen tortrix in two ways, by increasing the concentrations of positive factors (e.g. nitrogen) and decreasing the concentrations of negative factors (eg. carbon-based secondary metabolites) in leaves. Addition of purified aspen leaf condensed tannin and a methanol extract of young aspen leaves that contained condensed tannin and phenolic glycosides to artificial diets at high and low levels of dietary nitrogen supported this hypothesis. Increasing dietary nitrogen increased larval growth whereas increasing the concentrations of condensed tannin and phenolic glycosides decreased growth. Additionally, the methanol extract prevented pupation. These results indicate that future studies of woody plant/insect defoliator interactions must consider plant carbon/nutrient balance as a potentially important control over the nutritional value of foliage for insect herbivores.
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  • 3
    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
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