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  • 1
    Digitale Medien
    Digitale Medien
    The transfer of information in the dance language of honeybees: progress and problems (1993)
    Springer
    Journal of comparative physiology 173 (1993), S. 135-141 
    Details
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The dance language of honeybees will always be associated with the name of Karl von Frisch, who was one of the two founders of Zeitschrift für Vergleichende Physiologie, now the Journal of Comparative Physiology. The discovery of the dance language has already led to a great number of investigations of physiological mechanisms, and more studies can be expected in the future. It therefore seems most appropriate to let this King Solomon Lecture deal with the progress and problems in our efforts to understand the transfer of information in the dance language of honeybees.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00192972
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  • 2
    Digitale Medien
    Digitale Medien
    A new biophysical method to determine the gain of the acoustic trachea in bushcrickets (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 145-151 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Hearing ; Pressure difference receiver ; Bushcricket
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract A method is described for measuring the gain (i.e., the change of amplitude and phase angle) for sounds that propagate to the internal surface of the tympana in ears working as pressure difference receivers. The gain of the acoustic trachea has been measured in two similarly sized and closely related species of bushcrickets, in which the acoustic spiracles and tracheae differ markedly in size. The amplitude part of the gain is much larger in the species with the larger acoustic spiracle, whereas the phase part is very similar in the two species. The method is compared with other methods, which in the past have been used for estimating the gain of sound pathways inside animal bodies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215110
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  • 3
    Digitale Medien
    Digitale Medien
    Changes in the mechanics of the cricket ear during the early days of adult life (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 165-170 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Cricket ; Hearing ; Ontogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract From behavioural experiments it is known that the thresholds for both positive and the negative phonotaxis in crickets (Gryllus bimaculatus) decrease during the first days of adult life. Neuronal recordings have shown that a part of the changes in threshold has its origin in the ears. In this study we investigate some changes of the mechanics of the ears in the days after the imaginal moult. The posterior tympanum starts to work as an acoustic window only after the imaginal moult. During the first days the vibration amplitude tends to increase, except below 4 kHz and between 6 and 12 kHz. In the mature hearing organ, the tympanal vibrations exceed those of the surrounding cuticle up to ca. 50 kHz, and peaks of vibration amplitude are found around 5 and 15 kHz (the frequencies of the calling and courtship songs). The appearance of these peaks is caused, at least in part, by a change in the mechanics of the tympanum. Sound propagation through the trachea connecting the ipsilateral acoustic spiracle and the inner surface of the tympanum does not change much during the first week of adult life. In contrast, the propagation from the contralateral spiracle improves considerably. Thus the tympanum of the newly moulted cricket receives only little sound from the contralateral spiracle, and therefore the ear lacks the sound component which is essential for directional hearing in the mature cricket.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215112
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  • 4
    Digitale Medien
    Digitale Medien
    Physics of directional hearing in the cricket Gryllus bimaculatus (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 153-164 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Cricket ; Directional hearing Sound localization ; Laser vibrometry ; Pressure gradient
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract In the cricket ear, sound acts on the external surface of the tympanum and also reaches the inner surface after travelling in at least three pathways in the tracheal system. We have determined the transmission gain of the three internal sound pathways; that is, the change of amplitude and phase angle from the entrances of the tracheal system to the inner surface of the tympanum. In addition, we have measured the diffraction and time of arrival of sound at the ear and at the three entrances at various directions of sound incidence. By combining these data we have calculated how the total driving force at the tympanum depends on the direction of sound. The results are in reasonable agreement with the directionality of the tympanal vibrations as determined with laser vibrometry. At the frequency of the calling song (4.7 kHz), the direction of the sound has little effect on the amplitudes of the sounds acting on the tympanum, but large effects on their phase angles, especially of the sound waves entering the tracheal system at the contralateral side of the body. The master parameter for causing the directionality of the ear in the forward direction is the sound wave entering the contralateral thoracic spiracle. The phase of this sound component may change by 130–140° with sound direction. The transmission of sound from the contralateral inputs is dominated by a very selective high-pass filter, and large changes in amplitude and phase are seen in the transmitted sounds when the sound frequency changes from 4 to 5 kHz. The directionality is therefore very dependent on sound frequency. The transmission gains vary considerably in different individuals, and much variation was also found in the directional patterns of the ears, especially in the effects of sounds from contralateral directions. However, the directional pattern in the frontal direction is quite robust (at least 5 dB difference between the 330° and 30° directions), so these variations have only little effect on how well the individual animals can approach singing conspecifics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215111
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  • 5
    Digitale Medien
    Digitale Medien
    The effect of VA mycorrhizal fungi, phosphorus and drought stress on the growth of Acacia nilotica and Leucaena leucocephala seedlings (1990)
    Springer
    Plant and soil 124 (1990), S. 7-13 
    Details
    ISSN: 1573-5036
    Schlagwort(e): Acacia nilotica ; drought resistance ; drought stress ; Leucaena leucocephala ; nodulation ; reforestation ; VA mycorrhizal fungi
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effect of vesicular-arbuscular mycorrhizal (VAM) fungi on growth and drought resistance of Acacia nilotica and Leucaena leucocephala seedlings was studied in a glasshouse experiment. The experimental design was a 2·2·2 factorial: ± mycorrhizal inoculation, ± application of phosphorus fertilizer and ± repeated drought treatment. The growth promoting effect of VAM fungi equalled the effect of phosphorus fertilization after 12 weeks. The drought treatment reduced seedling biomass and nodulation. Differences between the plant species were found with respect to growth improvements due to VAM inoculation and/or phosphorus fertilization under drought stress conditions. The results are discussed in relation to plant drought resistance and reforestation in the subhumid to arid tropics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00010925
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  • 6
    Digitale Medien
    Digitale Medien
    Allelopathy in agroforestry systems: the effects of leaf extracts ofCupressus lusitanica and threeEucalyptus spp. on four Ethiopian crops (1993)
    Springer
    Agroforestry systems 21 (1993), S. 63-74 
    Details
    ISSN: 1572-9680
    Schlagwort(e): Cicer arietinum ; Eragrostis tef ; Pisum sativum ; tropical tree plantations ; Zea mays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The potential allelopathic effect ofCupressus lusitanica, Eucalyptus globulus, E. camaldulensis andE. saligna on seed germination, radicle and seedling growth was investigated with four crops:Cicer arietinum (chickpea),Zea mays (maize),Pisum sativum (pea) andEragrostis tef (teff). Aqueous leaf extracts of all the tree species significantly reduced both germination and radicle growth of the majority of the crops mostly starting from concentrations of 1% or 2.5%. The shoot and root dry weight increase of the crops was significantly reduced after 10 weeks treatment with leaf extracts. Among the four crops, chickpea and teff were most susceptible with respect to germination, and teff with respect to growth. From the overall data the leaf extracts of the four tree species can be arranged according to increasing allelopathic potential:C. lusitanica, E. globulus, E. saligna andE. camaldulensis. It is suggested that the planting ofE. camaldulensis andE. saligna in integrated land use systems should be minimized, whereas the use ofC. lusitanica andE. globulus seems less environmentally damaging in this respect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00704926
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