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  • Articles  (199)
  • Springer  (199)
  • 1985-1989  (199)
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  • Articles  (199)
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  • 1
    Electronic Resource
    Electronic Resource
    A Mössbauer study on the surface hyperfine field of uniform hematite particles (1988)
    Springer
    Applied physics 45 (1988), S. 245-247 
    Details
    ISSN: 1432-0630
    Keywords: 68.35 ; 76.00
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A Mössbauer spectroscopic study was performed on uniform spherical hematite particles (99±9 nm, Sample I) and those enriched with57Fe on the surface (Sample II). A striking difference was found between the spectra of these two samples, in that Sample I showed a spectrum with nearly symmetrical resonant absorption lines, while Sample II showed a spectrum with the lines broadened toward the central peaks asymmetrically. But after the57Fe-enriched sample was heated to 623 K, the spectral lines became narrower due to the diffusion of the surface57Fe-ions into the bulk. The above results showed that the centripetal broadening of the spectral lines for small uniform hematite particles resulted from a surface effect. The surface exhibited a hyperfine field about 5.2% lower than that for the bulk. The wider distribution of the surface hyperfine field was explained by structural inhomogeneity of the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615011
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  • 2
    Electronic Resource
    Electronic Resource
    Mössbauer studies of the Morin transition interval of uniform hematite particles (1988)
    Springer
    Hyperfine interactions 41 (1988), S. 483-486 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the vicinity of the Morin temperature Mossbauer spectra of uniform, non-uniform hematite particles and57Fe enriched on the surface of the uniform ones were measured. It was established that the wider the distribution of the particle size the larger the temperature interval of the Morin transition, but the surface effect did not affect the interval. The reason of existence of the Morin transition interval was explained based on theoretical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02400433
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  • 3
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    A M�ssbauer study on the surface hyperfine field of uniform hematite particles (1988)
    Springer
    Details
    Publication Date: 1988-03-01
    Print ISSN: 0947-8396
    Electronic ISSN: 1432-0630
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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    PAPER CURRENT
  • 4
    Electronic Resource
    Electronic Resource
    Bias in leaf area — sapwood area ratios and its impact on growth analysis in Pinus contorta (1988)
    Springer
    Trees 2 (1988), S. 104-109 
    Details
    ISSN: 1432-2285
    Keywords: Leaf area ; Sapwood cross-sectional area ; Production ; Leaf-area efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two alternative estimators of individual tree leaf area (A1) area are used to derive estimates of leaf-area index (L) for 40 plots in Pinus contorta Dougl. stands. One estimator of A1 is based on the common assumption of a constant ratio between A1 and sapwood cross-sectional area at breast height (As). The second estimator of A1 accounts for tree-to-tree variation in the relation between A1 and As. The apparent relationship between stand growth and leaf-area index is strongly dependent on the way leaf area is estimated. When L is derived from a constant A1∶As ratio, stand growth appears to be strongly correlated with L. However, when L is based on estmates of A1 that account for tree-to-tree variation in the A1 — As relation, stand growth is seen to be only weakly related to L. Stand structure, quantified as percent live-crown, accounts for a great deal of the observed variation in leaf-area efficiency. These contrasting relationships illustrate the importance of unbiased estimates of L in interpreting the link between stand-level processes and leaf area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196756
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  • 5
    Electronic Resource
    Electronic Resource
    Distribution and community structure of the benthic fauna of the north shore of the Gulf of St. Lawrence described by numerical methods of classification and ordination (1987)
    Springer
    Marine biology 95 (1987), S. 93-101 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The invertebrate benthic macrofauna of the northern part of the Gulf of St. Lawrence was sampled with a van Veen grab along a series of transects from 37 to 285 m in May, 1981. The pattern of spatial distribution was determined by classification and ordinastion techniques and by diversity and evenness statistics. Classification and ordination resulted in eleven station groups which could be divided into three broad faunal zones related to temperature, depth and sediment composition. The proportions of suspension feeders increased with sand content and nonselective deposit feeders increased with mud content. Faunal diversity decreased with depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447490
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  • 6
    Electronic Resource
    Electronic Resource
    Statoliths and microfilaments in plant cells (1989)
    Springer
    Planta 179 (1989), S. 275-278 
    Details
    ISSN: 1432-2048
    Keywords: Chara rhizoid ; Graviperception ; Lepidium root ; Microfilament ; Statolith
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microfilaments have been demonstrated in rhizoids of Chara fragilis Desvaux by labelling of actin with rhodamine-conjugated phalloidin. Each rhizoid contains thick microfilament-bundles arranged longitudinally in the basal region. In the subapical and apical regions, much thinner bundles exist which contact the statoliths and encircle them in the form of a dense envelope. In root statocytes from Lepidium sativum L. the presence of an actin network is indicated by the fact that application of cytochalasin B (25 μg·ml-1 for 4 h) results in an approximately threefold increase in the rate of statolith (amyloplast) sedimentation relative to controls. It is concluded that in gravity-perceiving plant cells statoliths may trigger the transduction mechanism via actin filaments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393699
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  • 7
    Electronic Resource
    Electronic Resource
    The role of carbon dioxide and oxygen in determining chlorophyll fluorescence quenching during leaf development (1985)
    Springer
    Planta 165 (1985), S. 477-485 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Leaf development (photosynthesis) ; Photoinhibition ; Triticum ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorophyll fluorescence emission at 680 nm (F680) and the rate of CO2 fixation were measured simultaneously in sections along the length of wheat and maize leaves. These leaves possess a basal meristem and show a gradation in development towards the leaf tip. The redox state of the primary electron acceptor, Q, of photosystem II was estimated using a non-invasive method. Distal mature leaf sections displayed typical F680 induction curves which were generally anti-parallel with CO2 fixation and during which Q became gradually oxidised. In leaf-base sections net assimilation of CO2 was not detectable, F680 quenched slowly and monotonously without displaying any of the oscillations typical of mature tissue and Q remained relatively reduced. Sections cut from mid-regions of the leaf showed intermediate characteristics. There were no major differences between the wheat and maize leaf in the parameters measured. The results support the hypothesis that generation of the transthylakoid proton gradient and associated ATP production is not a major limitation to photosynthesis during leaf development in either C3 or C4 plants. Removal of CO2 from the mature leaf sections caused little change in steady-state F680 and produced about 50% reduction of Q. When O2 was then removed, F680 rose sharply and Q became almost totally reduced. In immature tissue unable to assimilate CO2, removal of O2 alone caused a similar large rise in F680 and reduction of Q whilst removal of CO2 had negligible effects on F680 and the redox state of Q. It is concluded that in leaf tissue unable to assimilate CO2, either because CO2 is absent or the tissue is immature, O2 acts as an electron acceptor and maintains Q in a partially oxidised state. The important implication that O2 may have a role in the prevention of photoinhibition of the photochemical apparatus in the developing leaf is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398092
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  • 8
    Electronic Resource
    Electronic Resource
    Microscopic studies of cell divisions induced in alfalfa roots by Rhizobium meliloti (1987)
    Springer
    Planta 171 (1987), S. 289-301 
    Details
    ISSN: 1432-2048
    Keywords: Medicago ; Mutant (Rhizobium) ; nod genes ; Rhizobium ; Root nodule ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used spot-inoculation and new cytological procedures to observe the earliest events stimulated in alfalfa (Medicago sativa L.) roots by Rhizobium meliloti. Roots were inoculated with 1–10 nl of concentrated bacteria, fixed in paraformaldehyde, and after embedding and sectioning stained with a combination of acridine orange and DAPI (4′-6-diamidino-2-phenylindole hydrochloride). Normal R. meliloti provoke cell dedifferentiation and mitosis in the inner cortex of the root within 21–24 h after inoculation. This activation of root cells spreads progressively, leading to nodule formation. In contrast, the R. meliloti nodA and nodC mutants do not stimulate any activation or mitosis. Thus the primary and earliest effect of Rhizobium nod gene action is plant cellular activation. A rapid, whole-mount visualization by lactic acid shows that the pattern of nodule form varies widely. Some R. meliloti strains were found to be capable of stimulating on alfalfa roots both normal nodules and a “hybrid” structure intermediate between a nodule and a lateral root.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398674
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  • 9
    Electronic Resource
    Electronic Resource
    Gravitropic bending of cress roots without contact between amyloplasts and complexes of endoplasmic reticulum (1987)
    Springer
    Planta 172 (1987), S. 321-329 
    Details
    ISSN: 1432-2048
    Keywords: Endoplasmic reticulum complex ; Gravicurvature ; Graviperception ; Lepidium ; Root (graviperception) ; Statocyte polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The polar arrangement of cell organelles in Lepidium root statocytes is persistently converted to a physical stratification during lateral centrifugation (the centrifugal force acts perpendicular to the root long axis) or by apically directed centrifugation combined with cytochalasin-treatment. Lateral centrifugation (10 min, 60 min at 10\g or 50\g) causes displacement of amylplasts to the centrifugal anticlinal cell wall and shifting of the endoplasmic reticulum (ER) complex to the centripetal distal cell edge. After 60 min of lateral centrifugation at 10\g or 50\g all roots show a clear gravitropic curvature. The average angle of curvature is about 40° and corresponds to that of roots stimulated gravitropically in the horizontal position at 1\g in spite of the fact that the gravistimulus is 10-or 50-fold higher. Apically directed centrifugation combined with cytochalasin B (25 μg\ml-1) or cytochalasin D (2.5 μg\ml-1) incubation yields statocytes with the amyloplasts sedimented close to the centrifugal periclinal cell wall and ER cisternae accumulated at the proximal cell pole. Gravitropic stimulation for 30 min in the horizontal position at 1\g and additional 3 h rotation on a clinostat result in gravicurvature of cytochalasin B-treated centrifuged (1 h at 50\g) roots, but because of retarded root growth the angle of curvature is lower than in control roots. Cytochalasin D-treatment during centrifugation (20 min at 50\g) does not affect either root growth or gravicurvature during 3 h horizontal exposure to 1\g relative to untreated roots. As lateral centrifugation enables only short-term contact between the amyloplasts and the distal ER complex at the onset of centrifugation and apically directed centrifugation combined with cytochalasin-treatment even exclude any contact the integrity of the distal cell pole need not necessarily be a prerequisite for graviperception in Lepidium root statocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398660
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  • 10
    Electronic Resource
    Electronic Resource
    Sapwood area ofPinus contorta stands as a function of mean size and density (1986)
    Springer
    Oecologia 68 (1986), S. 410-412 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An indirect test of the relationship between leaf area and the combination of mean size and density is made in stands of lodgepole pine (Pinus contorta Dougl.). Total sapwood cross-sectional area of these stands is a function of the product of density and mean diameter raised to an exponent of about 1.6. Results from other studies, representing four species, suggest that this relationship between sapwood area and the combination of mean size and density may be general. The implications of the relationship are discussed in the context of evapotranspiration, competition and self-thinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01036747
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