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  • Articles  (49)
  • 2010-2014  (21)
  • 1995-1999  (28)
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  • Articles  (49)
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  • 1
    Electronic Resource
    Electronic Resource
    Production and cytogenetics of tetraploid–octoploid Avena hybrids (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 114 (1995), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The objectives of this research were to gather hybridization information about crosses between tetraploid and synthetically derived octoploid lines of Avena and their reciprocals, and to study the cytology of the hybrids obtained. When the octoploid plants were used as females, only 2.6% of the pollinated florets set seed, while seed set increased to 39.0% in reciprocal crosses. However, germination was 95.7% for the first group of hybrids and only 18.2% for the reciprocals. These diverse results can be explained by the paternal: maternal endosperm genomic ratios and the hypothesis of polar nuclei activation. The tetraploid-octoploid hybrids did not always contain 42 chromosomes. Octoploid lines derived indirectly from tetraploid (AABB) × hexaploid (AACCDD) crosses were found to retain their A and B genome chromosomes. Univalents in the above hybrids averaged 15.44 in 1990 and 15.15 in 1991, indicating the presence of C and D genome chromosomes inherited from the octoploid lines. Directly synthesized octoploids from diploid (AcAc) × hexaploid (AACCDD) crosses were found to form 20.44 univalents, 5.30 bivalents, and 2.69 trivalents when crossed with AABB tetraploid species. The high number of univalents indicates that chromosomes from at least three genomes, i.e. B, C, and D, remain unpaired, while trivalents are the result of homology between the A and Ac genomes. Hybrids between tetraploid and octoploid lines can be obtained at low frequencies but, regardless of the direction of the cross, these hybrids are highly sterile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1995.tb00778.x
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  • 2
    Electronic Resource
    Electronic Resource
    Geoid models around Sognefjord using depth data (1998)
    Springer
    Journal of geodesy 72 (1998), S. 547-556 
    Details
    ISSN: 1432-1394
    Keywords: Key words. Bathymetry ; Gravity ; Terrain effects ; Quasigeoid minus geoid ; Geoid ; GPS/levelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. Bathymetry data from Sognefjord, Norway, have been included in a terrain model, and their influence on the geoid has been calculated. The test area, located in the western part of Norway, was chosen due to its deep fjords and high mountains. Inclusion of bathymetry data in the terrain model altered the computed gravimetric geoid by as much as a few decimeters. The effect was detectable to a distance of more than 100 km. All calculated geoids, both with and without bathymetry data in the terrain model, fit the geoidal heights determined by available Global Positioning System (GPS) and levelling heights at the sub-decimetre level. Contrary to expectations, the accuracy in geoid prediction was reduced when using bathymetric data. The geoid changes were largest over the fjord where no GPS points were located. Different methods on the same area [isostatic and Residual Terrain Model (RTM)-terrain reductions] showed differences of approximately 1 m. Rigorous distinction between quasigeoid and geoid was found to be essential in this kind of area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050193
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  • 3
    Electronic Resource
    Electronic Resource
    Airborne gravimetry used in precise geoid computations by ring integration (1998)
    Springer
    Journal of geodesy 72 (1998), S. 600-605 
    Details
    ISSN: 1432-1394
    Keywords: Key words. Airborne gravimetry ; Gravity field extension ; Geoid computation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract. Two detailed geoids have been computed in the region of North Jutland. The first computation used marine data in the offshore areas. For the second computation the marine data set was replaced by the sparser airborne gravity data resulting from the AGMASCO campaign of September 1996. The results of comparisons of the geoid heights at on-shore geometric control showed that the geoid heights computed from the airborne gravity data matched in precision those computed using the marine data, supporting the view that airborne techniques have enormous potential for mapping those unsurveyed areas between the land-based data and the off-shore marine or altimetrically derived data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050198
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  • 4
    Electronic Resource
    Electronic Resource
    Endosperm Balance Number and the polar-nuclei activation hypotheses for endosperm development in interspecific crosses of Solanaceae and Gramineae, respectively (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 848-855 
    Details
    ISSN: 1432-2242
    Keywords: Endosperm development ; Evolution ; Imprinting ; Incompatibility ; Reciprocal crosses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Endosperm Balance Number (EBN) and the polar-nuclei activation (PNA) hypotheses have been developed to interpret, explain and predict interspecific and interploidy crossabilities in the Solanums and the Gramineae, respectively. Although these two hypotheses evolved independently, they share a number of common features. Assignment of EBNs and ‘activation/response values’ (AVs/RVs) depend on plumpness, size, and germinability of hybrid seeds. Also, both hypotheses emphasize the importance of a balanced parental genic contribution for the normal development of endosperm. However, in the EBN hypothesis a 2 maternal∶1 paternal EBN ratio is a prerequisite for successful interspecific crossability, while the PNA hypothesis is based on the stimulative strength of the male nuclei to initiate mitotic divisions in the primary endosperm nucleus and is idependent on a 2∶1 ratio between the RV of the polar nuclei and the AV of the male gamete. Differences and similarities betweeen the EBN and PNA hypotheses are summarized and contrasted. It is proposed that EBN and PNA be considered as the same concept.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223891
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  • 5
    Electronic Resource
    Electronic Resource
    Discovery of 2n gametes in tetraploid oat Avena vaviloviana (1995)
    Springer
    Euphytica 81 (1995), S. 1-6 
    Details
    ISSN: 1573-5060
    Keywords: Avena ; 2n gametes ; binucleate cell ; evolution ; sexual polyploidization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sexual polyploidization via the action of 2n gametes (gametes with the sporophytic chromosome number) has been identified as the most important evolutionary mode of polyploidization among plant genera. This study was conducted to determine whether 2n gametes are present in the tetraploid level of the genus Avena (2n=4×=28) Twenty tetraploid Avena lines, representing four species and one interspecific hybrid, were screened for pollen grain size in order to differentiate between n and 2n pollen. Avena vaviloviana (Malz.) Mordv. line PI 412767 was observed to contain large pollen grains at a 1.0% frequency. Cytogenetic analyses of pollen mother cells of PI 412767 revealed cells with double the normal chromosome number (i.e., 56 chromosomes at metaphase I and anaphase I). The mode of chromosome doubling was found to be failure of cell wall formation during the last mitotic division that preceded meiosis. The resulting binucleate cells underwent normal meiotic divisions and formed pollen grains with 28 chromosomes. Based on the formation and function of 2n gametes, three models involving diploid and tetraploid oat lines are proposed to describe possible evolutionary pathways for hexaploid oats. If stable synthetic hexaploid oat lines could be developed by utilizing 2n gametes from diploid and tetraploid oat species through bilateral sexual polyploidization, the resulting hexaploids could be used in breeding programs for transferring genes from diploids and tetraploids to cultivated hexaploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022452
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  • 6
    Electronic Resource
    Electronic Resource
    Pollen grain size in four ploidy levels of genusAvena (1995)
    Springer
    Euphytica 83 (1995), S. 103-108 
    Details
    ISSN: 1573-5060
    Keywords: oat ; Avena sativa ; pollen grain size ; chromosome number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pollen grain size in many genera positively correlated with chromosome number. In this study, oat (Avena) pollen grain size was examined in diploids (2×=14, one species, for accessions), tetraploids (4×=28, five species, 20 accessions), hexaploids (6×=42, one species, eight cultivars), and in 10 octoploid (8×=56) accessions. Mature anthers ready to dehisce pollen were sampled from one to six plants per accession, and pollen grains were squeezed out of the anther with tweezers. Oat pollen grains are slightly elliptical, and the length of the major axis was found to be highly correlated with the minor axis width (r=0.94**). Pollen grain length, 39.3 μm for diploids, 41.3 μm for tetraploids, 47.0 μm for hexaploids, and 48.8 μm for octoploids, was positively correlated (r=0.86**) with ploidy level. No genomic or species effects appeared to influence this trait. Only tetraploidAvena vaviloviana accession PI 412767 produced two distinct class sizes of pollen grains, 99% normal (43.0 μm) and 1% large (52.7 μm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01678036
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  • 7
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    Registration of ‘Bay’ Oat (1999)
    Wiley
    Details
    Publication Date: 1999-05-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 8
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    Greenland GPS network [Earth, Atmospheric, and Planetary Sciences] (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-07-25
    Description: The Greenland GPS Network (GNET) uses the Global Positioning System (GPS) to measure the displacement of bedrock exposed near the margins of the Greenland ice sheet. The entire network is uplifting in response to past and present-day changes in ice mass. Crustal displacement is largely accounted for by an annual oscillation superimposed on a sustained trend. The oscillation is driven by earth’s elastic response to seasonal variations in ice mass and air mass (i.e., atmospheric pressure). Observed vertical velocities are higher and often much higher than predicted rates of postglacial rebound (PGR), implying that uplift is usually dominated by the solid earth’s instantaneous elastic response to contemporary losses in ice mass rather than PGR. Superimposed on longer-term trends, an anomalous ‘pulse’ of uplift accumulated at many GNET stations during an approximate six-month period in 2010. This anomalous uplift is spatially correlated with the 2010 melting day anomaly.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Combined satellite altimetry and shipborne gravimetry data processing (1998)
    Taylor & Francis
    Details
    Publication Date: 1998-01-01
    Print ISSN: 0149-0419
    Electronic ISSN: 1521-060X
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Published by Taylor & Francis
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  • 10
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    Registration of ‘Kewaunee’ Barley (1999)
    Wiley
    Details
    Publication Date: 1999-05-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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