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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 2 (1979), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The concentration of sugar in the nectars of unprotected flowers of several species was measured and did not reach the high values that would be in equilibrium with the daytime humidities recorded outside the corolla, although the sugar concentration was highly correlated with ambient relative humidity. This paper examines features that maintain low nectar sugar concentrations at low ambient humidities. Post-secretory changes in concentration are influenced to a small extent by nectar composition but depend largely on physico-chemical and microclimatic effects. Factors contributing to the maintenance of steep gradients in water activity between the nectar and the ambient air include corolla morphology, sugar concentration gradients and waterproofing lipid monolayers on the nectar surface. This paper considers the relative importance of such features in relation to the pollination syndrome. A simple technique is described for the measurement of intrafloral relative humidity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 254 (1975), S. 437-439 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We now have evidence that integumentary waterproofing may be hormonally controlled. Weight loss is more rapid in decapitated cockroaches than in normal ones or in those in which nervous connection with the brain has been severed (Fig. 1). The involvement of a blood-borne factor is also indicated by ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 388 (1997), S. 165-167 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The phenomenon of ant-guarding on Acacia trees is probably the best known case of a mutualism between plants and animals, the ants conferring biotic defence against herbivores and perhaps against encroaching vegetation. However, as with many defence mutualisms, sometimes the interests of the ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0584-8547
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 50 (1989), S. 113-124 
    ISSN: 1570-7458
    Keywords: coffee ; solitary bees ; pollination ; entomophily ; Coffea canephora ; Creightonella frontalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Le café robusta, C. canephora, est une culture de rente dans de nombreuses régions intertropicales. La littérature le considère comme essentiellement pollinisé par le vent. Les caractéristiques de la fleur semblent contredire cette opinion. Nos observations montrent qu'en Nouvelle Guinée les fleurs sont typiquement entomophiles, étant avant tout pollinisées par des abeilles et des mouches. Des abeilles solitaires qui nichent dans les plantations, en particulier C. frontalis, sont de loin les plus importants et les plus réguliers visiteurs de ces fleurs. Les caractéristiques de la biologie et le comportement de nidification de cette abeille sont intimement liés à la production des buissons de caféier. Des mesures pour favoriser la pollinisation et améliorer la production de fruit dans les plantations de café sont ainsi suggérées.
    Notes: Abstract Lowland ‘robusta’ type coffee, (Coffea canephora), is a cash-crop in many tropical countries, and is reported in the literature as primarily wind-pollinated. The floral characteristics seem to refute this, and our evidence shows that in Papua New Guinea the flowers are classically entomophilous, being pollinated primarily by bees and flies. By far the most important and consistent visitors are solitary bees, especially Creightonella frontalis which nests within the plantations. The activity patterns and nesting biology of this bee are closely tied in with the success of the coffee bushes. Measures to improve pollination and fruit set in the coffee plantations are therefore suggested.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The flowers of Justicia aurea, morphologically characteristic of ornithophily, attracted a diverse array of foragers where they occurred as a dense stand in the tropical forests at La Selva, Costa Rica, and so provided an arena for this study of competition and coexistence. Two hummingbird species (Phaethornis superciliosus and Campylopterus hemileucurus) visited the flowers legally early in the morning, and defended the nectar resource; a third smaller bird (P. longuemareus) foraged for nectar throughout the day but collected it illegally by piercing the corollas. In addition, nectar was harvested illegally by four species of stingless bee (Trigona) and by ants, creating a further drain on the limited floral resources. Consideration of the diurnal patterns of foraging activities in combination with a spatial axis (defined here in terms of microclimate and insolation) nevertheless showed a good separation of flower visits for the different nectarivores. Hummingbirds visited flowers in zones where the reward was highest, while insects foraged to minimise their energetic costs; each of these factors could in turn be related to microclimatic considerations. A comprehensive scheme of resource utilisation could therefore be extracted from the field observations and interpreted in these terms. The limited area of niche overlap thus revealed corresponded closely with the situations where direct interference competition was observed, between hummingbird species or between bees and aggressive ants.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 51 (1981), S. 412-418 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Studies in Costa Rica on two ornithophilous flowers, Justicia aurea (Acanthaceae) and Columnea glabra (Gesneriaceae) showed a constancy of nectar solute concentrations that was attributed to microclimatic protection by the tubular corolla and to copious nectar secretion, helped by waterproofing by a lipid film on the nectar surface in Justicia and by preferential compass orientation of the flowers of Columnea. Most of the corollas in the patch of Justicia had been pierced by nectar-robbers. A consequence of this damage, together with local microclimate effects, was flower-to-flower variation in the amount and accessibility of nectar and in the nature and concentration of its minor components, notably amino acids. McDade and Kinsman's (1980) finding that nectar secretion could be suppressed by repeated sampling or by nectar-robbing was confirmed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 53 (1982), S. 382-385 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The flesh fly, Sarcophaga, is frequently seen feeding on flowers during periods of high radiation when other flies of comparable size avoid exposure because of the dangers of overheating. Sarcophaga is able to maintain its intermittent flower visits due to a cuticle of high thermal reflectance, giving low intrinsic heating rates, and to an ability to shunt blood between thorax and abdomen according to its needs. The fly thus achieves partial thermoregulation and can keep its body temperature within the preferred range for longer periods than its potential entomophilous competitors.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 47 (1980), S. 270-277 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The floral nectar of angiosperms is primarily a solution of simple sugars, but contains detectable amounts of other solutes, particularly amino acids. These have been regarded as diagnostic, for phylogenetic and taxonomic purposes, and their mean concentrations may be significant in relation to the pollination syndrome of a plant species. However, in several temperate flowers the amino acid concentration varied by an order of magnitude when measured at intervals through a single day. In open, cup-shaped flowers, this was partly due to post-secretory equilibration with the varying humidity of the air. But the effects of floral visitation by insects on nectar amino acids were also important, both in open flowers and in those with long corollas and more enclosed nectar. Visitors could add amino acids to nectar by direct contact, by salivation, by damaging the neighbouring tissues causing cell leakage, and by dislodging pollen into the nectar; the importance of each of these effects varied according to corolla morphology and the spectrum of visitors.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 50 (1981), S. 250-255 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper outlines simple techniques for determining rates of heat gain and loss in relation to the weight and reflectance of insects caught in their natural habitats. In particular the construction of a new ‘reflectometer’ is described. The results thus obtained permit estimates of the relative importance of size and colour in determining rates of heat exchange and temperature excesses, so allowing better predictions of heat budgets for a given species.
    Type of Medium: Electronic Resource
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