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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 97 (1994), S. 512-519 
    ISSN: 1432-1939
    Keywords: Plant invasion ; Drought acclimation Hawaii ; Heteropogon contortus ; Pennisetum setaceum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The alien grass, Pennisetum setaceum, dominates many of the lowland arid regions that once supported native Heteropogon contortus grassland on the island of Hawaii. Response to drought in a glasshouse was compared between these C4 grasses to test if success as an invader is related to drought tolerance or plasticity for traits that confer drought tolerance. Pennisetum produced 51% more total biomass, allocated 49% more biomass to leaves, and had higher net photosynthetic rates (P n) on a leaf area basis than Heteropogon. Plants of both species under drought produced less total biomass and increased their allocation to roots compared to well-watered plants, but there was no difference between the two species in the magnitude of these responses. The decline in P n with decreasing leaf water potential (ψ1) was greater for Pennisetum compared to Heteropogon. Plasticity in the response of P n to ψ1, osmotic potentials, and the water potentials at turgor loss in response to drought were not different between the two species. Stomata were more responsive to Δw in Heteropogon than in Pennisetum and for well-watered plants compared to droughted plants. Plasticity for the stomatal response to Δw, however, was not different between the species. There was no evidence that the alien, Pennisetum, had greater plasticity for traits related to drought tolerance compared to the native, Heteropogon. Higher P n and greater biomass allocation to leaves resulted in greater growth for Pennisetum compared to Heteropogon and may explain the success of Pennisetum as an invader of lowland arid zones on Hawaii.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 77 (1988), S. 468-479 
    ISSN: 1432-1939
    Keywords: Size-selective predation ; Community structure ; Predation intensity ; Seasonal ; Species sorting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The zooplankton community of a small pond changed markedly with temporal variation in predation pressure. Long term changes in zooplankton community structure occurred following the replacement of planktivorous fish by phantom midge (Chaoborus americanus) larvae as the predominant predator of zooplankton. The interannual changes following the establishment of Chaoborus included the apparent or near extinction, of species ill adapted to the new predation pressure and the successful colonization of well adapted species. Seasonal changes in the species composition and size distribution of the zooplankton community correlate with temporal variation in predation intensity associated with temperature-activity patterns of the predator or changes in the stage structure of the predator population.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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