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  • 1990-1994  (4)
  • Life and Medical Sciences  (2)
  • calcium  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A re-examination of phosphorus-lime interactions in perennial ryegrass (1991)
    Springer
    Plant and soil 135 (1991), S. 185-196 
    Details
    ISSN: 1573-5036
    Keywords: calcium ; critical phosphorus concentration ; gypsum ; lime ; perennial ryegrass ; root membranes ; soluble carbohydrate ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The results of a previous study had suggested that under conditions of limited P availability, Ca may be able to compensate for P in the shoot tissue of perennial ryegrass. To verify this preliminary finding, a factorial experiment was set up which simultaneously tested the effects of Ca and P fertilization on the yield and chemical composition of perennial ryegrass. Calcium was supplied as either lime or gypsum in order to differentiate between the effects of Ca and pH on the response of perennial ryegrass to P fertilization. In the final stage of the experiment a Zn treatment was included, to see whether altering the P/Zn ratios of plant shoots had any influence on the purported interaction between Ca and P. The results demonstrated that the P-sparing effect of lime occurs, at least partly, because Ca application improves the efficiency of absorbed P for DM production. However, it was reasonably clear that the site of the interaction between Ca and P was the soil-root interface, and not shoot tissue. It was suggested that under conditions of limited P supply, Ca stablizes root membranes and thereby minimizes both the efflux losses of nutrients from root tissue, and the compensatory flow of photosynthates from shoots to roots. No interaction was observed between P and Zn treatments in this study. Instead, a positive interaction was found between lime and Zn treatments, which suggests that the stabilizing action of Ca on root membranes requires Zn as a co-stabilizing factor. It is proposed that chemical analysis of shoot tissue alone may not be sufficient to accurately diagnose the P, Ca or Zn status of whole plants, since the critical levels of these elements in shoots appear to bear little relation to their requirements in the rhizosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010906
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of gypsum on the uptake, assimilation and cycling of 15N-labelled ammonium and nitrate-N by perennial ryegrass (1992)
    Springer
    Plant and soil 143 (1992), S. 19-31 
    Details
    ISSN: 1573-5036
    Keywords: ammonium ; calcium ; carboxylate/organic nitrogen ratio ; 15N isotope ; nitrate ; nitrogen cycling ; perennial ryegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Solution culture studies have shown that plant uptake of NH4 + and NO3 - can be improved by increasing the concentration of Ca2+ in the root environment: the same may be true for grass grown in soil culture. An experiment was set up to see whether gypsum (CaSO4 2H2O) increased the rate at which perennial ryegrass absorbed 15NH4 + and 15NO3 - from soil. The results demonstrated that gypsum increases the rates of uptake of both NH4 + and NO3 - by perennial ryegrass. However because there was little potential for mineral-N loss from the experimental system, either by gaseous emission or by N immobilization, long term improvements in fertilizer efficiency were not observed. Nitrogen cycling from shoots to roots commenced once net uptake of N into plants had ceased. Labelled N transferred thus to roots underwent isotopic exchange with unlabelled soil N. It was suggested that this exchange of N might constitute an energy drain from the plant, if plant organic N was exchanged for soil inorganic N. The fact that the exchange occurred at all cast doubt on the suitability of the 15N-isotope dilution technique for assessing fertilizer efficiency in medium to long term experiments. There was evidence that the ‘extra’ NO3 --N taken up by plants on the all-nitrate treatments as a result of gypsum application, was reduced in root tissue rather than in shoots, but to the detriment of subsequent root growth and N uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009125
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of cold shock and phospholipase A2 on intact boar spermatozoa and sperm head plasma membranes (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 143-149 
    Details
    ISSN: 1040-452X
    Keywords: Fertility ; Ca2+ uptake ; Head plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes (HPM) isolated from cryopreserved boar spermatozoa show an excessive fluidization (Buhr et al., Gamete Res 23:441-449, 1989), which might be involved in the loss of fertility. The current study assessed the ability of cold shock (5°C) and phospholipase A2 (PA2) to duplicate these effects on membrane structure and to affect 45Ca2+ uptake and gross morphological characteristics of whole, fresh boar sperm. The HPM from cold-shocked sperm showed a significantly greater rate of fluidization over time than did HPM from control sperm. Addition of PA2 (bee or snake venom, 0.1 or 10.0 ng/ml) to HPM from control sperm caused fluidization similar to cold shocking, but to a lesser degree (P 〈 0.05). Cold-shocked intact sperm exhibited severe acrosomal disruption, loss of motility, and increased 45Ca2+ uptake relative to control sperm. Addition of PA2 (bee or snake venom, 0.1, 1.0., 10.0, and 1,000 ng/ml) to control sperm had not effect on gross morphology or motility while maintaining or increasing sperm extrusion of 45Ca2+. Therefore, although PA2 can, to some extent, duplicate the effects of cold shock on HPM molecular organization, its lipid hydrolytic action is insufficient to cause all the gross disruptions of severe thermal shock. Both PA2 and cold shock disrupted HPM structure, but only cold shock increased 45Ca2+ uptake, suggesting that cold shock may be increasing 45Ca2+ uptake in areas other than the head. Cold shock disrupts sperm on three levels; membrane molecular organization, intracellular Ca2+ regulation, and gross morphology/motility.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080260208
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of ethanol dehydration and critical point drying on fish tissue culture cell membrane elemental composition by scanning electron microscopy/X-ray microanalysis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 259-260 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070280310
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    Paper (German National Licenses)
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