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  • 1
    Electronic Resource
    Electronic Resource
    Induced responses in three alkaloid-containing plant species (1993)
    Springer
    Oecologia 95 (1993), S. 425-430 
    Details
    ISSN: 1432-1939
    Keywords: Senecio jacobaea ; Cynoglossum officinale ; Catharanthus roseus ; Alkaloids ; Induced responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we test three plant species for the inducibility of their alkaloid production. The plants were heavily damaged by cutting off 50% of their leaf surface using a pair of scissors. The cut-off leaf tips were used as controls for possible diurnal fluctuations. After 3, 6, 12, 24 and 48 h, respectively, the leaf bases of the damaged plants were harvested and the alkaloid concentration was measured. In Senecio jacobaea the pyrrolizidine alkaloid (Pa) concentration in damaged plants decreased within 6–12 h after damage. Within 24 h after damage the Pa concentration of Cynoglossum officinale doubled compared to control values. Indole alkaloid production in Catharanthus roseus was found not to be induced in this experiment. The responses are discussed in a functional context. We hypothesize that the nature of the response is not a feature of the type of secondary metabolite, but is related to whether the plants are damaged mainly by generalist or by specialist herbivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320998
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  • 2
    Electronic Resource
    Electronic Resource
    Tritrophic interactions between aphids (Aphis jacobaeae Schrank), ant species, Tyria jacobaeae L., and Senecio jacobaea L. lead to maintenance of genetic variation in pyrrolizidine alkaloid concentration (1991)
    Springer
    Oecologia 86 (1991), S. 177-182 
    Details
    ISSN: 1432-1939
    Keywords: Senecio jacobaea ; Tritrophic interactions ; Genetic variation ; Pyrrolizidine alkaloids ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We hypothesize that the tritrophic interaction between ants, the aphid Aphis jacobaeae, the moth Tyria jacobaeae, and the plant Senecio jacobaea can explain the genetic variation observed in pyrrolizidine alkaloid concentration in natural populations of S. jacobaea. The ant Lasius niger effectively defends S. jacobaea plants infested with A. jacobaeae against larvae of T. jacobaeae. S. jacobaea plants with A. jacobaeae which are defended by ants escape regular defoliation by T. jacobaeae. Plants with aphids and ants have a lower pyrrolizidine alkaloid concentration than plants without aphids and ants. When these data are fitted to an existing theoretical model for temporal variation in fitness it is shown that varying herbivore pressure by T. jacobaeae in interaction with ants defending aphid-infested plants with a low pyrrolizidine alkaloid concentration can lead to a stable polymorphism in pyrrolizidine alkaloid concentration. Costs of the production and maintenance of pyrrolizidine alkaloids are not accounted for in the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317529
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  • 3
    Electronic Resource
    Electronic Resource
    Pattern of storage and regrowth in ragwort (2000)
    Springer
    Evolutionary ecology 14 (2000), S. 439-455 
    Details
    ISSN: 1573-8477
    Keywords: compensatory growth ; competition ; damage ; herbivory ; intraspecific variation ; plasticity ; storage of resources ; tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ragwort plants were damaged experimentally by removing the whole shoot. Within about 1 month the original allocation pattern of biomass to root and shoot was reestablished to a large extent. If left undisturbed for a longer period, plant growth accelerated into compensatory growth. Intraspecific variation in storage and tolerance (shoot weight), 1 month after damage, was significant. We could not detect a trade-off between storage or tolerance and relative growth rate of control plants. Consequently there are no indications for costs involved in storage of resources or in tolerating damage. Although tolerance is thought to be dependent upon storage of resources, we detected no effect of storage on tolerance after one event of damage. Storage is genotype specific, but at the same time highly plastic. We hypothesize that the value of storage in ragwort only becomes evident after repeated disturbances. Competition, history of herbivory and change of season all affected storage radically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010985028360
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  • 4
    Electronic Resource
    Electronic Resource
    The “Raison D'être” of pyrrolizidine alkaloids inCynoglossum officinale: Deterrent effects against generalist herbivores (1995)
    Springer
    Journal of chemical ecology 21 (1995), S. 507-523 
    Details
    ISSN: 1573-1561
    Keywords: Cynoglossum officinale ; Boraginaceae ; pyrrolizidine alkaloids ; chemical defense ; specialist herbivores ; generalist herbivores ; Ethmia bipunctella ; Mogulones (Ceutorhynchus) cruciger ; Spodoptera exigua ; Helix aspersa ; Frankliniella occidentalis ; Locusta migratoria ; Lyriomyza trifolii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In this study we tested whether pyrrolizidine alkaloids (PAs) ofCynoglossum officinale serve as antifeedants against herbivores. Total PA N-oxide extracts of the leaves significantly deterred feeding by generalist herbivores. Specialist herbivores did not discriminate between food with high and low PA levels. Three PAs fromC. officinale, heliosupine, echinatine, and 3′-acetylechinatine, equally deterred feeding by the polyphagous larvae ofSpodoptera exigua. Although the plants mainly contain PAs in their N-oxide form, reduced PAs deterred feeding byS. exigua more efficiently than PA N-oxides. On rosette plants, the monophagous weevilMogulones cruciger significantly consumed more of the youngest leaves, which had the highest PA level and the highest nitrogen percentage. Larvae ofEthmia bipunctella, which are oligophagous within the Boraginaceae, did not discriminate between leaves. All generalist herbivores tested significantly avoided the youngest leaves with the highest PA levels. In the field, the oldest leaves also were relatively more damaged by herbivores than the youngest leaves. It is hypothesized that the skewed distribution of PAs over the leaves of rosette plants reflects optimal defense distribution within the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02033698
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  • 5
    Electronic Resource
    Electronic Resource
    Involvement of strictosidine as a defensive chemical inCatharanthus roseus (1996)
    Springer
    Journal of chemical ecology 22 (1996), S. 1355-1366 
    Details
    ISSN: 1573-1561
    Keywords: Antifeedant ; fungi ; bacteria ; Spodoptera exigua ; Catharanthus roseus ; Fusarium solani ; Fusarium oxysporum ; Trichoderma viride ; Cladosporium cucumerinum ; Phytophthora infestans ; strictosidine ; strictosidine glucosidase ; indole alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The involvement of the glucoalkaloid strictosidine in antimicrobial and antifeedant activity inCatharanthus roseus leaves was investigated. Strictosidine and its deglucosylation product, specifically formed by the enzyme strictosidine glucosidase, were shown to be active against several microorganisms. In contrast, neither the intact glucoside, nor the aglycone product(s) was found to exhibit antifeedant activity againstSpodoptera exigua larvae, as was found for intactC. roseus leaves and leaf extracts. Besides alkaloids further downstream in the biosynthesis pathway, a more apolar, yet unidentified compound may be involved in this activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02027718
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