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  • 1975-1979  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Open Learning or Open Access? Some questions from the institutional viewpoint (1979)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of educational technology 10 (1979), S. 0 
    Details
    ISSN: 1467-8535
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Education
    Notes: This paper looks at the current emphasis in open learning from the institutional point of view as the eventual provider. It outlines the current trends towards distance learning, considers the implications of them for institutional organization and compares them with other forms of opening up learning opportunities for individuals. In particular the problems and advantages of various college study schemes are outlined and the implications for individual institutions discussed. The paper draws on what evidence is available but does not attempt to provide solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1467-8535.1979.tb00376.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Farnesol-like antitranspirant activity and stomatal behaviour in maize and Sorghum lines of differing drought tolerance (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 2 (1979), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Potted seedlings of four lines of maize and Sorghum of differing drought tolerance were subjected to a single soil drying cycle and were only rewatered when the plants showed the first signs of wilting. Other plants remained well-watered throughout the experimental period. As plant water potentials decreased in the unwatered plants of three of the lines investigated (Sorghum Piper and M35-1, V-4146 and maize Farz 27), endogenous levels of farnesol-like antitranspirants increased. Closure of stomata correlated well with the increase in endogenous antitranspirant. In the fourth line (Sorghum M35-1, V-4184), stomata did not close as the level of plant water stress increased, although leaf diffusion resistance of even the well-watered plants of this line was quite high. In this line, there was no consistent relationship between plant water stress and antitranspirant level or between stomatal behaviour and antitranspirant level. The involvement of farnesol-like antitranspirants in the control of stomatal behaviour in water-stressed plants is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1979.tb00773.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    EEC directives (reply) (1975)
    [s.l.] : Nature Publishing Group
    Nature 258 (1975), S. 192-192 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR,-I am not prepared to accept the whole of Lord Ashby's thesis, contained in his comments on the EEC pollution debate. He states, for instance, that "rabid conservationists need to be reminded sometimes that all pollution, except that from atomic weapons, is a by-product of processes which ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/258192c0
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Solute regulation and growth by roots and shoots of water-stressed maize plants (1979)
    Springer
    Planta 147 (1979), S. 43-49 
    Details
    ISSN: 1432-2048
    Keywords: Growth ; Roots ; Shoots ; Solute accumulation ; Water stress ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Potted maize seedlings were subjected to a single period of water stress. As the severity of water stress increased, measurements were made of leaf and root solute and water potentials, leaf diffusive conductance and leaf and root growth. After day four of the drying cycle, the rate of leaf extension and the development of leaf area were reduced. This reduction correlated well with a reduction in leaf turgor which occurred at this time. A significant accumulation of solutes in the root tips of the unwatered plants resulted in the maintenance of root turgor for the duration of the water stress treatment. Root growth of the unwatered plants was also maintained as the severity of water stress increased. A mild degree of water stress resulted in a net increase in root growth compared to the situation in well-watered plants. The significance of solute regulation and continued root growth for plants growing in drying soil is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384589
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Solute accumulation in leaves and roots of woody plants subjected to water stress (1978)
    Springer
    Oecologia 32 (1978), S. 323-332 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Young seedlings of English Oak, Quercus robur L., and Silver Birch, Betula verrucosa Ehrl., were subjected to a number of consecutive periods during which water was withheld. During one 14-day period leaf-and soil-water potentials and leaf- and root-solute potentials of two groups of plants were sampled at noon of each day. One group of plants was watered every day while water was withheld from the other group. Solute accumulation in roots and leaves of oak seedlings subjected to water stress resulted in maintenance of turgor and high leaf conductance as the soil dried. In birch seedlings turgor was only maintained by stomatal closure at high soil water potential. Fourteen consecutive water stress cycles greatly reduced the growth of birch seedlings but had little effect on oak seedlings other than to alter root morphology. Water stress treatment resulted in the production of long thin roots in this plant. Stomatal behaviour in oak and birch seedlings during the 14-week stress period was consistent with observed changes in leaf water and solute potentials. Daily solute accumulation in oak leaves was presumably responsible for the maintenance of plant growth as water potentials fell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345110
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Variations among woody plants in stomatal conductance and photosynthesis during and after drought (1977)
    Springer
    Plant and soil 46 (1977), S. 435-444 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Acer saccharum, Fraxinus americana, Juglans nigra, Acer rubrum, Cornus amomum, and Ulmus americana seedlings were subjected to a soil drying cycle and then rewatered. At frequent intervals during the drying cycle and following rewatering, determinations were made of equilibrium photosynthesis rates, leaf conductances and leaf water potentials. As the drying cycle progressed, leaf water potentials decreased, stomata closed, and rates of transpiration and photosynthesis were reduced. Stomata of the two Acer species initially were more sensitive to water stress than were those of the other species. At low leaf water potentials, stomata of Juglans and Cornus were more open than those of the other species. Photosynthesis of Acer saccharum, Fraxinus and Juglans was significantly reduced by plant water stress, while photosynthetic water use efficiency of Cornus and Juglans was most unfavourable. Photosynthesis/leaf conductance ratios in water stressed leaves were higher in Fraxinus than in the other species. Immediately after rewatering, only limited stomatal opening occurred in Acer saccharum and Cornus with recovery of stomatal opening most protracted in Fraxinus and Ulmus. There was extended reduction of photosynthesis of all species as a result of the soil drying treatment. This effect was most significant in Acer saccharum and Juglans. Survival of plants on moist and dry sites is discussed in relation to stomatal control of transpiration and metabolic responses to water stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010099
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    Paper (German National Licenses)
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