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  • 1
    Digitale Medien
    Digitale Medien
    Physiological effects of long-term exposure to low and moderate concentrations of atmospheric NH3 on poplar leaves (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. Poplar shoots (Populus euramericana L.) obtained from cuttings were exposed for 6 or 8 weeks to NH3 concentrations of 50 and 100 μgm−3 or filtered air in fumigation chambers. After this exposure the rates of NH3 uptake, transpiration, CO2 assimilation and respiration of leaves were measured using a leaf chamber. During the long-term exposure also modulated chlorophyll fluorescence measurements were carried out to obtain information about the photosynthetic performance of individual leaves. Both fluorescence and leaf chamber measurements showed a higher photosynthetic activity of leaves exposed to 100 μg NH3 m−3. These leaves showed also a larger leaf conductance and a larger uptake rate of NH3 than leaves exposed to 50 μg m−3 NH3 or filtered air. The long-term NH3 exposure did not induce an internal resistance against NH3 transport in the leaf, nor did it affect the leaf cuticle. So, not only at a short time exposure, but also at a long-term exposure NH3 uptake into leaves can be calculated from data on the boundary layer and stomatal resistance for H2O and ambient NH3-concentration. Furthermore, the NH3 exposure had no effect on the relation between CO2-assimilation and stomatal conductance, indicating that NH3 in concentrations up to 100 μg m−3 has no direct effect on stomatal behaviour; for example, by affecting the guard or contiguous cells of the stomata.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01969.x
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  • 2
    Digitale Medien
    Digitale Medien
    Growth of Populus euramericana (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 57 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Growth curves of successive leaves of Populus euramericana (Dode) Guinier ‘Robusta’ have been determined. With ample supply of water and nutrients the growth of a poplar shoot follows a fixed pattern: an initial logarithmic acceleration phase followed by a stationary phase in which leaves of equal size are produced at a constant rate. Analysis of growth curves of leaves enabled the growth curves of leaf primordia to be predicted. These primordial growth curves are compared to the indirectly determined growth curves of primordia by measuring the lengths of successive leaf primordia in the apex during the stationary phase of growth. The increase in length of successive leaves in the acceleration phase of growth continues for a longer period at high than at low irradiace. The relative growth rates of leaf primordia, leaves and internodes are discussed in terms of shoot growth and phyllotaxis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb02768.x
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  • 3
    Digitale Medien
    Digitale Medien
    Photosynthesis of Desiccating Leaves of Poplar (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 34 (1975), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The relation between photosynthesis and water content was investigated using detached leaves of Populus euramericana (Dode) Guinier cv. Robusta.The time course of photosynthesis was measured at different light intensities, at different CO2 contents of the air and at constant temperature during the desiccation of the leaves. The time course of decreasing water content was obtained from continuous measurement of water transpired from the leaves.A large reduction of light saturated (400 W × m−2) photosynthetic rates was observed with decreasing water contents between 78 and 64% (water potential between −14 and −24 atm (bar)). This reduction was much greater in air with 0.3 % CO2 than in air with 5 % CO2, indicating a significant influence of CO2 diffusion resistance on rate of photosynthesis. The reduction of the rate of light and CO2 saturated photosynthesis (at 400 W × m–2 and 5% CO2 in the air) is a measure of the inactivation of the photosynthetic enzyme system by desiccation. A proportional reduction of the light saturated and light limited rate of photosynthesis (for different H2O contents) was found, when measured in air containing a saturating amount of CO2 (5 %). The reduction of the light limited rate of photosynthesis (at 20 W × m−2) was the same at both CO2 levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1975.tb01856.x
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  • 4
    Digitale Medien
    Digitale Medien
    Physiological effects of long term exposure to low concentrations of SO2 and NH3 on poplar leaves (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 82 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Shoots of poplar (Populus euramericana L. cv. Flevo) were exposed to filtered air, SO2, NH3 or a mixture of SO2 and NH3 for 7 weeks in fumigation chambers. After this exposure gas exchange measurements were carried out using a leaf chamber. As compared to leaves exposed to filtered air, leaves pretreated with 112 μg m−3 SO2 showed a small reduction in maximum CO2 assimilation rate (Pmax) and stomatal conductance (gs). They also showed a slightly higher quantum yield and dark respiration. In addition, the fluorescence measurements indicated that the Calvin cycle of the leaves pretreated with 112 μg m−3 SO2 was more rapidly activated after transition from dark to light. An exposure to 64 μg m−3 NH3 had a positive effect on Pmax, stomatal conductance and NH3 uptake of the leaves. This positive effect was counteracted by an SO2 concentration of 45 μg m−3. The exposure treatments appeared to have no effect on the relationship between net CO2-assimilation and gs. Also, no injury of the leaf cuticle or of epidermal cells was observed.Resistance analysis showed that NH3 transfer into the leaf can be estimated from data on the boundary layer and stomatal resistance for H2O transfer and NH3 concentration at the leaf surface, irrespective of whether the leaves are exposed for a short or long time to NH3 or to a mixture of NH3 and SO2. In contrast SO2 uptake into the leaves was only partly correlated to the stomatal resistance. The results suggest a large additional uptake of this gas by the leaves. The possibility of a difference in path length between SO2 and H2O molecules is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb02899.x
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  • 5
    Digitale Medien
    Digitale Medien
    The chromosomes of esox lucius L. (1955)
    Springer
    Genetica 27 (1955), S. 484-488 
    Details
    ISSN: 1573-6857
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Esox lucius (the pike) is found to have 48 rod-shaped chromosomes with completely terminal centromeres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01664175
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