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  • 1
    Electronic Resource
    Electronic Resource
    Auxin-induced growth and its linkage to potassium channels (1997)
    Springer
    Planta 201 (1997), S. 227-234 
    Details
    ISSN: 1432-2048
    Keywords: Auxin-induced growth ; Channel blocker ; Donna ; Potassium channel ; Tetraethylammonium ; Zea (auxin-induced growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the potassium dependence of rapid auxin-induced growth of scrubbed maize (Zea mays L. cv. Garant) coleoptile segments by means of positional angular transducers. Our setup permitted six simultaneous high-resolution measurements. Provided a buffer with a high concentration of calcium was used in conjunction with well-abraded coleoptiles, (i) there was no auxin-induced growth in the absence of K+ions, whereas in the presence of 1–10 mM KCl auxin-induced growth could be detected after a lag phase of 20 min; (ii) auxin-pretreated plants, which were not growing in the absence of K+ions displayed an instantaneous growth burst if 1–10 mM KCl was added; (iii) this burst of growth did not occur in the absence of auxin, excluding the possibility that it was due to “stored” endogenous growth and (iv) it could not be triggered by Cl-, confirming that it was not an anion effect. The effect was. specific for monovalent cations and showed an apparent selectivity for K+ and Rb+, but was not observed with Li+ or Na+. The action of 1 mM K+ was reversibly blocked by 10–30 mM tetraethylammonium (TEA) and 5 mM Ba2+. Measurements of auxin-induced proton secretion using a computer-controlled pH-stat revealed a similar dependency on the ionic composition of the bathing medium and a similar inhibition by TEA. We suggest that both auxin-induced growth and proton secretion strictly depend on extracellular K+ions and the uptake of K+ mediated by K+ channels at the plasma membrane. These results generally support the acid-growth theory of auxin action, and also concur with evidence that auxin modulation of K+ channels plays a role in the signalling cascade leading to auxin-induced cell elongation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007708
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  • 2
    Electronic Resource
    Electronic Resource
    Herkunft, Wirkung und Synthese der Ibhaltsstoffe des Haschisch (1966)
    Springer
    Naturwissenschaften 53 (1966), S. 541-546 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00602952
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  • 3
    Electronic Resource
    Electronic Resource
    Übersicht über die Pfeffer-Festschrift (1915)
    Springer
    Naturwissenschaften 3 (1915), S. 131-136 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01546012
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  • 4
    Electronic Resource
    Electronic Resource
    Charged particle erosion of solid rare gases and dilute rare gas alloys (1982)
    Springer
    Applied physics 29 (1982), S. 57-61 
    Details
    ISSN: 1432-0630
    Keywords: 79.20. −m ; 61.80. −x ; 71.35. +z
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We present the first experimental results on electron-induced erosion of solid neon. The measurements are interpreted qualitatively within a new model invoking excitation transport by free excitons and their subsequent decay at the surface. The model accounts for the magnitude of the observed yield and the energy dependence. A theoretically predicted decrease in the erosion yield due to doping with a heavier rare gas, in casu argon, has been observed experimentally. The strong influence of very small amounts of different types of impurities makes sample purity a crucial problem in investigations of the erosion of solid rare gases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00632426
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  • 5
    Electronic Resource
    Electronic Resource
    Variability of global biome patterns as a function of initial and boundary conditions in a climate model (1996)
    Springer
    Climate dynamics 12 (1996), S. 371-379 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. The use of one-way coupling of an equilibrium-response vegetation, or biome, model with atmospheric circulation models is critically assessed. Global biome patterns from various, equally likely numerical realisations of present-day climate are compared. It has been found that the changes in global biome patterns to be expected from interdecadal variability in the atmosphere affect 9–12% of the continental surface (Antarctica excluded). There is no unique difference pattern, although changes are mainly induced by the variability of annual moisture availability and, to a lesser extent, by winter temperatures. This variability of biome patterns reflects the uncertainty in the estimate of equilibrium vegetation patterns from finite time interval climatologies. Changes in biome distributions between present-day climate and anomaly climate, the latter induced by an increase in sea-surface temperatures and atmospheric CO2, are larger than and different in kind from the changes due to inderdecadal variability. Roughly 30% of the land surface is affected by these changes. It appears that the strongest and most significant signal is seen for boreal biomes which can be attributed to an increase in near surface temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050114
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  • 6
    Electronic Resource
    Electronic Resource
    The impact of sub-grid scale sea-ice inhomogeneities on the performance of the atmospheric general circulation model ECHAM3 (1996)
    Springer
    Climate dynamics 12 (1996), S. 477-496 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. Leads and polynyas have a great impact on the energy budget of the polar ocean and atmosphere. Since atmospheric general circulation models are not able to resolve the spatial scales of these inhomogeneities, it is necessary to include the effect of fractional sub-grid scale sea-ice inhomogeneities on climate by a suitable parametrization. In order to do this we have divided each model grid-cell into an ice-covered and an ice-free part. Nevertheless, a numerical model requires effective transports representative for the whole grid-box. A simple procedure would be to use grid averages of the surface parameters for the calculation of the surface fluxes. However, as the surface fluxes are non-linearly dependent on the surface properties, the fluxes over ice and open water should be calculated separately according to the individual surface-layer structure of each surface type. Then these local fluxes should be averaged to obtain representative fluxes. Sensitivity experiments with the Hamburg atmospheric general circulation model ECHAM3 clearly show that a subgrid scale distribution of sea ice is a dominant factor controlling the exchange processes between ocean and atmosphere in the Arctic. The heat and water vapour transports are strongly enhanced leading to a significant warming and moistening of the polar troposphere. This affects the atmospheric circulation in high- and mid-latitudes; e.g. the stationary lows are modified and the transient cyclonic activity over the subpolar oceans is reduced. A pronounced impact of sub-grid scale sea-ice distribution on the model climate can only be obtained when the non-linear behaviour of the surface exchange processes is considered by a proper, physically based, averaging of the surface fluxes. A simple linear averaging of surface parameters is not sufficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050122
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  • 7
    Electronic Resource
    Electronic Resource
    Modeling bio-geophysical feedback in the African and Indian monsoon region (1997)
    Springer
    Climate dynamics 13 (1997), S. 247-257 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract.  An asynchronously coupled global atmosphere-biome model is used to assess the dynamics of deserts and drought in the Sahel, Saudi-Arabia and the Indian subcontinent. Under present-day conditions of solar irradiation and sea-surface temperatures, the model finds two solutions: the first solution yields the present-day distribution of vegetation and deserts and the second shows a northward spread of savanna and xerophytic shrub of some 600 km, particularly in the southwest Sahara. Comparison of atmospheric states associated with these solutions corroborates Charney’s theory of a self-induction of deserts through albedo enhancement in the Sahel. Over the Indian subcontinent, changes in vegetation are mainly caused by a positive feedback between increased soil moisture and stronger summer monsoon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050164
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  • 8
    Electronic Resource
    Electronic Resource
    Mid-Holocene greening of the Sahara: first results of the GAIM 6000 year BP Experiment with two asynchronously coupled atmosphere/biome models (2000)
    Springer
    Climate dynamics 16 (2000), S. 643-659 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract  The mid-Holocene `green' Sahara represents the largest anomaly of the atmosphere-biosphere system during the last 12 000 years. Although this anomaly is attributed to precessional forcing leading to a strong enhancement of the African monsoon, no climate model so far has been able to simulate the full extent of vegetation in the Sahara region 6000 years ago. Here two atmospheric general circulation models (LMD 5.3 and ECHAM 3) are asynchronously coupled to an equilibrium biogeography model to give steady-state simulations of climate and vegetation 6000 years ago, including biogeophysical feedback. The two model results are surprisingly different, and neither is fully realistic. ECHAM shows a large northward extension of vegetation in the western part of the Sahara only. LMD shows a much smaller and more zonal vegetation shift. These results are unaffected by the choice of `green' or modern initial conditions. The inability of LMD to sustain a `green' Sahara 6000 years ago is linked to the simulated strength of the tropical summer circulation. During the northern summer monsoon season, the meridional gradient of sea-level pressure and subsidence over the western part of northern Africa are both much weaker in ECHAM than in LMD in the present as well as the mid-Holocene. These features allow the surface moist air flux to penetrate further into northern Africa in ECHAM than in LMD. This comparison illustrates the importance of correct simulation of atmospheric circulation features for the sensitivity of climate models to changes in radiative forcing, particularly for regional climates where atmospheric changes are amplified by biosphere-atmosphere feedbacks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820000074
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  • 9
    Electronic Resource
    Electronic Resource
    Biomes computed from simulated climatologies (1994)
    Springer
    Climate dynamics 9 (1994), S. 235-243 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. The biome model of Prentice et al. (1992a) is used to predict global patterns of potential natural plant formations, or biomes, from climatologies simulated by ECHAM, a model used for climate simulations at the Max-Planck-Institut für Meteorologie. This study is undertaken in order to show the advantage of this biome model in diagnosing the performance of a climate model and assessing effects of past and future climate changes predicted by a climate model. Good overall agreement is found between global patterns of biomes computed from observed and simulated data of present climate. But there are also major discrepancies indicated by a difference in biomes in Australia, in the Kalahari Desert, and in the Middle West of North America. These discrepancies can be traced back to failures in simulated rainfall as well as summer or winter temperatures. Global patterns of biomes computed from an ice age simulation reveal that North America, Europe, and Siberia should have been covered largely by tundra and taiga, whereas only small differences are seen for the tropical rain forests. A potential north-east shift of biomes is expected from a simulation with enhanced CO2 concentration according to the IPCC Scenario A. Little change is seen in the tropical rain forest and the Sahara. Since the biome model used is not capable of predicting changes in vegetation patterns due to a rapid climate change, the latter simulation has to be taken as a prediction of changes in conditions favourable for the existence of certain biomes, not as a prediction of a future distribution of biomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003820050022
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  • 10
    Electronic Resource
    Electronic Resource
    Biomes computed from simulated climatologies (1994)
    Springer
    Climate dynamics 9 (1994), S. 235-243 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The biome model of Prentice et al. (1992a) is used to predict global patterns of potential natural plant formations, or biomes, from climatologies simulated by ECHAM, a model used for climate simulations at the Max-Planck-Institut fur Meteorologie. This study is undertaken in order to show the advantage of this biome model in diagnosing the performance of a climate model and assessing effects of past and future climate changes predicted by a climate model. Good overall agreement is found between global patterns of biomes computed from observed and simulated data of present climate. But there are also major discrepancies indicated by a difference in biomes in Australia, in the Kalahari Desert, and in the Middle West of North America. These discrepancies can be traced back to failures in simulated rainfall as well as summer or winter temperatures. Global patterns of biomes computed from an ice age simulation reveal that North America, Europe, and Siberia should have been covered largely by tundra and taiga, whereas only small differences are seen for the tropical rain forests. A potential northeast shift of biomes is expected from a simulation with enhanced C02 concentration according to the IPCC Scenario A. Little change is seen in the tropical rain forest and the Sahara. Since the biome model used is not capable of predicting changes in vegetation patterns due to a rapid climate change, the latter simulation has to be taken as a prediction of changes in conditions favourable for the existence of certain biomes, not as a prediction of a future distribution of biomes.[/ab]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208255
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