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  • 1
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    The renormalon contribution to the current product j μ5 j S (1999)
    Springer
    Details
    Publication Date: 1999-05-01
    Print ISSN: 1434-6001
    Electronic ISSN: 1434-601X
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Molecular markers to differentiate two morphologically-close species of the genus Sitobion (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 217-225 
    Details
    ISSN: 1570-7458
    Keywords: Sitobion avenae ; Sitobion fragariae ; RAPD ; PCR ; microsatellites ; mtDNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A set of molecular markers to differentiate the aphid (Hemiptera: Aphidoidea) species Sitobion avenae (Fabricius) from Sitobion fragariae (Walker), is presented. These markers correspond to (1) a region of the mitochondrial DNA, (2) five species-specific RAPD banding patterns and (3) four microsatellite loci. Each of the markers was able to clearly distinguish between the species. The utility of each molecular marker is discussed. Mitochondrial DNA is best applicable to species determination and relative abundance, RAPDs to the evaluation of genetic diversity, and microsatellites to the assessment of the population genetic structure; the combined use of mtDNA with the other techniques can be of importance when the presence of hybrids is suspected, and RAPDs with microsatellites are best used together in population genetics and host preference studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003855919065
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  • 3
    Electronic Resource
    Electronic Resource
    Salivation into sieve elements in relation to plant chemistry: the case of the aphid Sitobion fragariae and the wheat, Triticum aestivum (1999)
    Springer
    Entomologia experimentalis et applicata 91 (1999), S. 111-114 
    Details
    ISSN: 1570-7458
    Keywords: sieve element ; salivation ; aphid ; plant resistance ; wheat ; Sitobion fragariae ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extended sieve element salivation (E1 waveform in the electrical penetration graph) is a characteristic activity during early sieve element punctures, particularly in resistant plants. In order to explore a chemically-mediated mechanism of resistance associated with sieve element salivation, we compared the pattern of feeding behaviour of the aphid, Sitobion fragariae (Walker), on two cultivars of the wheat Triticum aestivum L., with different concentrations of hydroxamic acids (Hx). During 24 h of electronic monitoring, aphids dedicated over 50% of the total time to phloem ingestion from the sieve elements. Total time allocated to E1 in the experiment, time to first E1 within the experiment, time allocated to E1 before a sustained phloem ingestion (E2) and the contribution of sieve element salivation to the phloem phase (E1/[E1+E2]) were significantly higher in the high-Hx cultivar. The increased salivation in plants with higher contents of Hx suggests the existence, at least in this system, of a chemically-mediated sieve element constraint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003628703035
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  • 4
    Electronic Resource
    Electronic Resource
    Within-plant allocation of a chemical defense in Secale cereale. Is concentration the appropriate currency of allocation? (1999)
    Springer
    Chemoecology 9 (1999), S. 113-117 
    Details
    ISSN: 1423-0445
    Keywords: Key words. defense allocation — hydroxamic acids — leaf age — optimal defense theory — rye —Secale cereale— Poaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age, leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000490050041
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of Dimboa Analogs as Antifeedants and Antibiotics Towards the Aphid Sitobion avenae in Artificial Diets (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1543-1554 
    Details
    ISSN: 1573-1561
    Keywords: Aphids ; Sitobion avenae ; feeding deterrents ; antibiotics ; DIMBOA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A total of 25 compounds including benzoxazinones, benzoxazolinones, and N-glyoxylamide derivatives were tested as antifeedants and antibiotics towards the aphid Sitobion avenae in diet bioassays. The antifeedant and mortality indexes increased with the presence of electron-donating groups in the 7 position of the benzoxazinone moiety, the replacement of the oxygen atom by sulfur in the heterocyclic ring, the presence of a hemiacetal instead of an acetal at C-2 of the benzoxazine moiety (and hence the possibility of ring opening), and the presence of a hydroxyl group at C-4 of the benzoxazine moiety (hydroxamic acid) instead of a hydrogen atom (lactam). The results support earlier hypotheses on the chemical bases for the mode of action of these compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020832731546
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  • 6
    Electronic Resource
    Electronic Resource
    Intraspecific Chemical Recognition in the Lizard Liolaemus tenuis (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1799-1811 
    Details
    ISSN: 1573-1561
    Keywords: Liolaemus lizards ; conspecific chemical recognition ; tongue-flick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Experimental tests were conducted to determine whether females and males of the tree-dwelling lizard Liolaemus tenuis (Tropiduridae) show intraspecific chemical recognition during breeding and postreproductive seasons. Animals were individually maintained in plastic enclosures for one week. Thereafter, the number of tongue-flicks that a lizard performed in the enclosure of a male, a female, its own home enclosure, and a control (unused) enclosure were recorded. In both seasons, males and females made fewer tongue-flicks in their home enclosures than in any other one, indicating a recognition of a familiar place, probably a chemical self-recognition. Conspecific chemical recognition was season dependent. During the post-reproductive season, lizards tongue-flicked at similar rates in conspecific and control enclosures, while during the breeding season enclosures of females elicited more tongue-flicks by both sexes, and the overall tongue-flick rates were higher than in the postreproductive season. Results are discussed within the context of the social system of the species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020925631314
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  • 7
    Electronic Resource
    Electronic Resource
    Defoliation Affects Chemical Defenses in All Plant Parts of Rye Seedlings (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 491-499 
    Details
    ISSN: 1573-1561
    Keywords: Defoliation ; regrowth ; induced responses ; chemical defense ; hydroxamic acids ; rye ; Secale cereale ; Poaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effect of defoliation and consecutive defoliation (condefoliation) of rye seedlings on the allocation patterns of biomass and hydroxamic acids (Hx) was evaluated five days after treatment. Growth of condefoliated seedlings was lower than that of defoliated and nondefoliated ones. Concentration of Hx decreased in shoots of condefoliated seedlings compared to nondefoliated ones, while concentration of Hx in root exudates increased. Allocation of Hx to roots and root exudates increased at the expense of allocation to the shoots in condefoliated seedlings. The ratio of Hx-aglucone to Hx-glucoside was higher in shoots of defoliated and condefoliated seedlings. The decrease in quantity of defense in shoots was accompanied by an increase in its quality, given that aglucones are more toxic than glucosides. The increase in concentration of Hx—an allelopathic compound also involved in mineral uptake by roots—in root exudates of condefoliated seedlings was suggested to lead to an advantage in the acquisition of resources for the regeneration of lost biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020945602297
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Previous Exposure to Hydroxamic Acids in Probing Behavior of Aphid Sitobion fragariae on Wheat Seedlings (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 771-779 
    Details
    ISSN: 1573-1561
    Keywords: Aphid ; experience ; probing behavior ; sieve elements ; salivation ; cell punctures ; hydroxamic acids ; EPG ; Sitobion fragariae ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We hypothesized that aphids after previous exposure to hydroxamic acids (Hx), a family of secondary plant compounds deleterious to aphids, are able to reduce their subsequent exposure to them. This hypothesis was tested by evaluating the time to produce salivation into a sieve element (SSE) by the aphid Sitobion fragariae on seedlings of two wheat cultivars of Triticum aestivum differing in their concentration of Hx. The total time to produce a first SSE was significantly longer in the high-Hx cultivar; however, the subsequent, second SSE (first SSE after interruption of probing) in this cultivar was significantly reduced, reaching the level observed in the low-Hx plants. Therefore, a strategy to reduce the exposure to secondary compounds was observed only in the second SSE in high-Hx plants. When the experimental plant was replaced by a new unattacked plant after the first SSE, aphids did not change the behavior described, thus excluding an aphid-induced plant susceptibility. The number of cell punctures and accumulated duration was not affected by previous exposure to Hx, either in low or high Hx cultivars. Total time and pathway time but not cell punctures, seem to be the variables affected by previous exposure to Hx.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020836515674
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  • 9
    Electronic Resource
    Electronic Resource
    Host-Plant Chemicals and Distribution of Neuquenaphis on Nothofagus (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1043-1054 
    Details
    ISSN: 1573-1561
    Keywords: Nothofagus ; Neuquenaphis ; volatiles ; olfactometry ; α-agarofuran
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Extractable metabolites from leaves (EM) and volatiles released from six Nothofagus species were analyzed by TLC and GC-MS, respectively. Aphids of the genus Neuquenaphis, closely associated to Nothofagus, were sampled on each Nathofagus species. Cluster analyses of Nothofagus species were performed based on the presence or absence of EM and volatiles. Dissimilarity distances, from the cluster analyses of EM and volatiles, were used to evaluate their association with the aphid distribution. A major component identified from EM and volatiles of three species of Nothofagus, α-agarofuran, was attractive to alates of the oligophagous Neuquenaphis sensoriata, which use them as hosts. These results suggest that chemicals play a significant role in the host-plant associations between Neuquenaphis and Nothofagus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020825707922
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  • 10
    Electronic Resource
    Electronic Resource
    The renormalon contribution to the current product j μ5 j S (1999)
    Springer
    The European physical journal 5 (1999), S. 91-95 
    Details
    ISSN: 1434-601X
    Keywords: PACS:12.38.Lg Other nonperturbative calculations – 14.20.Dh Protons and neutrons – 13.85.Qk Inclusive production with identified leptons, photons, or other nonhadronic particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The product of an axialvector and a scalar current and its relation to the chiral-odd distribution function h 1 is discussed in the framework of the renormalon approach. Using a bag-model calculation for h 1, we calculate its intrinsic uncertainty due to renormalon poles. The result is given as a function of Bjorken-x as well as for the first moments separately.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500050261
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