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Digitale Medien

Comparison of the effect of hydroxamic acids from wheat on five species of cereal aphids (1995)

Givovich, Arturo ; Niemeyer, Hermann M.

Springer

Entomologia experimentalis et applicata 74 (1995), S. 115-119

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ISSN: 1570-7458

Schlagwort(e): wheat ; aphids ; hydroxamic acids ; DIMBOA ; DIMBOA-glucoside ; EPG ; electrical penetration graph ; feeding deterrents ; antixenosis ; plant resistance

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Feeding behaviour of five species of cereal aphids in wheat seedlings differing in hydroxamic acid (Hx) levels, was monitored via electrical penetration graphs (EPG). Aphid species could be grouped as sensitive to the feeding deterrent effect of Hx in the seedlings (Rhopalosiphum padi, Schizaphis graminum, Sitobion avenae, andMetopolophium dirhodum) or insensitive to them (Rhopalosiphum maidis). However, when feeding behaviour was studied in artificial diets containing Hx, all species were equally sensitive to Hx. The behavour ofR. maidis was further compared with that ofR. padi through detailed EPG analysis. It was found that the insensitivity ofR. maidis to Hx in seedlings may be due to a feeding strategy avoiding contact with the compounds by decreasing the number of cellular punctures in live tissues other than sieve elements during its way to the phloem.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02383002

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Digitale Medien

Salivation into sieve elements in relation to plant chemistry: the case of the aphid Sitobion fragariae and the wheat, Triticum aestivum (1999)

Ramírez, Claudio C. ; Niemeyer, Hermann M.

Springer

Entomologia experimentalis et applicata 91 (1999), S. 111-114

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ISSN: 1570-7458

Schlagwort(e): sieve element ; salivation ; aphid ; plant resistance ; wheat ; Sitobion fragariae ; Triticum aestivum

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: 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.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1003628703035

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Digitale Medien

QCD sum rules with finite masses (1995)

Meyer-Hermann, M. ; Schäfer, A. ; Greiner, W.

Springer

The European physical journal 351 (1995), S. 345-351

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ISSN: 1434-601X

Schlagwort(e): 12.38.-t ; 12.38.Lg ; 14.65.-q

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract The concept of QCD sum rules is extended to bound states composed of particles with finite mass such as scalar quarks or strange quarks. It turns out that mass corrections become important in this context. The number of relevant corrections is analyzed in a systematic discussion of the IR- and UV-divergencies, leading in general to a finite number of corrections. The results are demonstrated for a system of two massless quarks and two heavy scalar quarks.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01290918

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Digitale Medien

Characteristics of Hydroxamic Acid Induction in Wheat Triggered by Aphid Infestation (1997)

Gianoli, Ernesto ; Niemeyer, Hermann M.

Springer

Journal of chemical ecology 23 (1997), S. 2695-2705

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ISSN: 1573-1561

Schlagwort(e): Defense ; herbivory ; aphids ; wheat ; Gramineae ; hydroxamic acids ; Defense theory ; Carbon/Nutrient theory

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract Hydroxamic acids (Hx) are natural products of Gramineae that are associated with cereal resistance to pests. We aimed at characterizing the induction of Hx accumulation in seedlings of wheat,Triticum aestivum, by short-term infestation of the cereal aphid,Rhopalosiphum padi. A load of 25 aphids increased significantly the Hx levels in the infested primary leaf in comparison with control levels. Lower loads did not increase Hx concentration. Aphid infestation lasting 16 hr did not elicit induction of Hx, even after a time-lag of 32 hr to allow the expression of any induced response. Forty-eight hours was the minimum duration of aphid infestation required to trigger Hx induction. The age of the infested tissue (the primary leaf) did not affect induction. Similar increases of Hx were found in unfolding, expanding, and totally expanded primary leaves. It was determined that the regime of nutrient supply (N-intensive nutritive solutions at low and high concentration) to wheat seedlings had no effect on the magnitude of the aphid-induced Hx (N-based secondary metabolites). Results obtained are discussed in the framework of general theories of plant defense allocation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1022554708782

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Digitale Medien

Environmental Effects on the Accumulation of Hydroxamic Acids in Wheat Seedlings: The Importance of Plant Growth Rate (1997)

Gianoli, Ernesto ; Niemeyer, Hermann M.

Springer

Journal of chemical ecology 23 (1997), S. 543-551

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ISSN: 1573-1561

Schlagwort(e): Temperature ; photoperiod ; hydroxamic acids ; growth ; defense ; secondary metabolites ; wheat ; Gramineae

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract The effects of temperature and photoperiod on accumulation of hydroxamic acids (Hx) in wheat (Triticum aestivum L.) seedlings were evaluated under laboratory conditions. Hx concentrations were significantly higher at higher temperatures. No such clear trend was found for the photoperiod effect. The significant effect of temperature and photoperiod on growth rate of seedlings and the significant positive correlation between growth rate prior to analysis and levels of Hx, suggested that environmental effects on Hx accumulation were at least partially mediated through their effect on plant growth rate. After uncoupling the effect of environmental conditions from the effect of plant growth rate by statistical means the effect of temperature on Hx was no longer significant. Therefore, temperature effect was fully mediated by plant growth rate. Implications of the patterns found are discussed in issues of plant-defense general theories.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/B:JOEC.0000006376.92876.14

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