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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
    ISSN: 1432-1106
    Keywords: Otolith ; Semicircular canal ; Vestibular deafferentation ; Centrifuge ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We recorded three-dimensional eye movements during angular acceleration steps from 0 to 250°/s at 20°/s2 about an earth-vertical axis. Experiments were performed on 27 normal subjects and on 19 patients who had recovered well from unilateral vestibular deafferentation on the right or left side. In addition to compensatory horizontal eye movements, significant vertical and torsional eye movement components were elicited. These vertical and torsional eye velocity traces led to a shift of the axis of eye velocity away from the axis of head velocity. Horizontal, vertical, and torsional velocity components showed clear differences between normals and patients with unilateral vestibular deafferentation. In normals, the axis of eye velocity tilted backward and slightly away from the axis of head velocity. Patients showed similar, but more pronounced, shifts during rotations toward the intact ear and shifts in the opposite direction for rotations toward the operated ear. Eye velocity traces were analyzed with special consideration given to the orientation of the axis of eye velocity. We speculate that the vertical and torsional velocity components may be due to the effects of Listing's plane, as well as the contributions of the otolith signals.
    Type of Medium: Electronic Resource
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