Voici les éléments 1 - 4 sur 4
  • Publication
    Métadonnées seulement
    An elicitor of plant volatiles from beet armyworm oral secretion
    (1997)
    Alborn, Hans
    ;
    ;
    Jones, Tappey
    ;
    Stenhagen, G
    ;
    Loughrin, John H
    ;
    Tumlinson, James H
    The compound N-(17-hydroxylinolenoyl)-L-glutamine (named here volicitin) was isolated from oral secretions of beet armyworm caterpillars. When applied to damaged leaves of corn seedlings, volicitin induces the seedlings to emit volatile compounds that attract parasitic wasps, natural enemies of the caterpillars. Mechanical damage of the leaves, without application of this compound, did not trigger release of the same blend of volatiles. Volicitin is a key component in a chain of chemical signals and biochemical processes that regulate tritrophic interactions among plants, insect herbivores, and natural enemies of the herbivores.
  • Publication
    Métadonnées seulement
    Herbivore-induced volatile emissions from cotton (Gossypium-hirsutum L) seedlings
    (1994)
    McCall, Philip J
    ;
    ;
    Loughrin, John H
    ;
    Proveaux, Adron T
    ;
    Tumlinson, James H
    The effect of herbivory on the composition of the volatile blends released by cotton seedlings was investigated by collecting volatiles from undamaged, freshly damaged (0-2 hr after initiation of feeding), and old damaged (16-19 hr after initiation of feeding) plants on which com earworm caterpillars (Helicoverpa zea Boddie) were actively feeding. A blend of 22 compounds was consistently observed to be emitted by the old damaged plants with nine occurring either only in, or in significantly greater amounts in old damaged, as compared with freshly damaged plants. These were (Z)-3-hexenyl acetate, hexyl acetate, (E)-beta-ocimene, (3E)-4,8-dimethyl-1,3,7-nonatriene, (Z)-3-hexenyl butyrate, (E)-2-hexenyl butyrate, (Z)-3-hexenyl 2-methylbutyrate, (E)-2-hexenyl 2-methylbutyrate, and indole, The nature of this response is compared with other studies where herbivore-induced volatile responses are also known. The presence of large amounts of terpenes and aldehydes seen at the onset of feeding and the appearance of other compounds hours later suggest that cotton defense mechanisms may consist of a constitutive repertoire that is augmented by an induced mechanism mobilized in response to attack. A number of the induced compounds are common to many plants where, in addition to an immediate defensive function, they are known to be involved in the attraction of natural enemies.
  • Publication
    Métadonnées seulement
    Semiochemically mediated foraging behavior in beneficial parasitic insects
    (1993)
    Tumlinson, James H
    ;
    ;
    Lewis, W Joe
    Chemical cues enable female parasitic wasps to locate the eggs, larvae, or other life stages of the insects in or on which they place their eggs. These chemical signals, or semiochemicals, may be produced by the hosts and/or by the plants on which the hosts feed. The composition of the chemical signal often differs with different species of hosts or with different plants. New evidence suggests that the wasps exploit semiochemicals emitted by plants in response to insect herbivore feeding. The wasps learn to respond to the different blends of chemicals that indicate the location of their hosts and they can be trained to respond to a specific odor blend. Thus, it may be possible to increase their effectiveness for biological control by conditioning them, prior to their release, to search for a target pest in a particular crop.
  • Publication
    Métadonnées seulement
    Systemic release of chemical signals by herbivore-injured corn
    (1992) ;
    Tumlinson, James H
    Corn seedlings respond to insect herbivore-inflicted injury by releasing relatively large amounts of several characteristic terpenoids and, as a result, become highly attractive to parasitic wasps that attack the herbivores. Chemical evidence showed that the induced emission of volatiles is not limited to the sites of damage but occurs throughout the plant. This evidence was obtained by comparing the release of volatiles from leaves of unharmed (control) seedlings with the release of volatiles from undamaged leaves of seedlings with two injured leaves treated with caterpillar regurgitant. Immediately after injury no differences were measured in the released volatiles, but several hours later the undamaged leaves of injured plants released the terpenoids linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene in significantly larger amounts than leaves of unharmed plants. Other volatiles that are released by herbivore-injured leaves were detected occasionally only in trace amounts from the undamaged leaves of a damaged seedling. The systemic release of volatiles by injured corn coincided with attractiveness to the parasitoid Cotesia margin-iventris; undamaged leaves of injured plants became significantly more attractive than leaves from control seedlings. These findings show conclusively that when a plant is injured by an insect herbivore the whole plant emits chemical signals.