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  • 1985-1989  (6)
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Materialart
Erscheinungszeitraum
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    The effect of temperature and ageing on root apical meristems during seedling growth of Triticum aestivum L.: a specific effect on nucleoli (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. Growth and cytology of root apical meristems of Chinese Spring wheat were studied in relation to temperature. The maximum rate of growth increased with temperature, a marked rise occurring between 10°C and 12°C. At all temperatures studied nucleolar volume increased to a maximum and then declined. The maximum nucleolar size achieved showed particular temperature sensitivity, higher volumes being attained at lower temperatures. The peak at 5°C was 70% higher than at 20°C. However, in comparison, cell and nuclear volumes were only 38% and 47% larger, respectively. Ultrastructural analysis of the nucleoli revealed a temperature-dependent relationship between the proportion of granular component and dense fibrillar component. The results are discussed in relation to the regulation of ribosome synthesis and function during growth and development at different temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1985.tb01406.x
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  • 2
    Digitale Medien
    Digitale Medien
    Cytological Evidence for Fertilization in Hexaploid Wheat × Sorghum Crosses (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 100 (1988), S. 0 
    Details
    ISSN: 1439-0523
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Crosses were made between the hexaploid wheat ‘Chinese Spring’ (2n = 42) and the diploid grain sorghum ‘S9B’ (2n = 20). Sixty-nine out of 100 florets fixed 48 h after pollination contained an embryo, an endosperm, or both, a remarkably high frequency in view of the taxonomic distance spanned by the cross. Percentages of single or double fertilization ranged from 50 % to 91 % for individual spikes. The hybrid origin of the embryos was confirmed by examining zygotes from spikes fixed 25 to 27 h after pollination. Seven of the 8 zygotes in which chromosomes were sufficiently contracted to be counted contained 21 large wheat chromosomes and 10 much smaller sorghum chromosomes. The eighth contained 21 chromosomes from wheat and 20 from sorghum. Sorghum chromosomes did not appear to be attached to the spindle in zygote nietaphases and showed no evidence of movement towards the spindle poles in the single zygote anaphase found. Embryos with two or more cells invariably contained one or more micronuclei and metaphases in embryos with three or more cells contained only 21 wheat chromosomes showing that sorghum chromosomes were rapidly eliminated. Endosperm, when present, was always highly abnormal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1439-0523.1988.tb00220.x
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  • 3
    Digitale Medien
    Digitale Medien
    The absence of the somatic association of centromeres of homologous chromosomes in grass mitotic metaphases (1988)
    Springer
    Chromosoma 96 (1988), S. 119-131 
    Details
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Root-tip metaphases from Hordeum vulgare (19 cells), H. marinum (11 cells), Aegilops umbellulata (10 cells) and Zea mays (10 cells) were completely reconstructed from electron micrographs of serially sectioned nuclei. The identity of each chromosome was found by measuring the volumes of its two arms and the presence or absence of a secondary constriction at the nucleolar organising region. With the position of the centromere in three dimensions, these data were used to analyse the relative positions of homologous and heterologous centromeres. In 31 out of the 50 cells analysed, homologues were on average further apart than heterologues. Except for two nucleolar organising chromosomes, there was no evidence of any tendency for the distances between different homologue types to be differently distributed from distances between heterologues. Average distances between homologues of the single nucleolar organising chromosome (linkage group 6) of Zea (2n = 20) were lower than the average for heterologues and the interhomologue distances were distributed significantly differently from the separation distances of chromosome 6 to other chromosomes. Presumably this association occurred because of nucleolar fusion in the previous interphase. Homologues of one of the two nucleolar organising chromosomes of A. umbellulata were also distributed significantly differently from heterologues, with a tendency for homologues to lie farther apart than the average heterologous pair. These results do not support previous work using squashed and spread metaphase preparations (some including abnormal, marked chromosomes) for these species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00331044
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  • 4
    Digitale Medien
    Digitale Medien
    The volumes and morphology of human chromosomes in mitotic reconstructions (1989)
    Springer
    Human genetics 〈Berlin〉 84 (1989), S. 27-34 
    Details
    ISSN: 1432-1203
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Ten unpretreated normal human male fibroblast cells in mitosis were completely reconstructed from micrographs of between 82 and 119 consecutive serial sections. All 46 chromosomes and their centromeres could be reconstructed in every cell. Measurements of chromosome volumes and centromere indices are presented. The data enabled allocation of all chromosomes to their groups (A to G), and chromosomes 1, 2, 3, 6, 9, 16, 17, 18 and Y were individually identified. Comparisons with published karyotypes showed that volume measurements correlated well with measurements of DNA content and chromosome length. Centromere indices also showed good correlation, but the acrocentric chromosomes were more unequally armed than found by length measurement. Secondary constrictions at the nucleolar organising region were visible on about a third of the acrocentric chromosomes. One chromosome of the C group, number 9, had a diffuse subcentromeric region (DSR) on the long arm, at the position of the constitutive heterochromatin and (in meiotic cells) the paramere.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00210666
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  • 5
    Digitale Medien
    Digitale Medien
    The effect of the crossability loci Kr1 and Kr2 on fertilization frequency in hexaploid wheat x maize crosses (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 403-409 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Wheat ; Maize ; Crossability genes ; Chromosome elimination ; Haploids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Dominant alleles of the Kr1 and Kr2 genes reduce the crossability of hexaploid wheat with many alien species, including rye and Hordeum bulbosum, with Kr1 having the greater effect. However, a cytological study of wheat ovaries fixed 48 h after pollination showed that the wheat genotypes ‘Highbury’ (kr1, Kr2) and ‘Chinese Spring (Hope 5B)’ (kr1, kr2) were crossable with ‘Seneca 60’ maize, fertilization occurring in 14.4 and 30.7% of embryo sacs respectively. The latter figure was similar to the 29.7% fertilization found in ‘Chinese Spring’ (kr1, kr2). Most embryo sacs in which fertilization occurred contained an embryo but lacked an endosperm and where an endosperm was formed it was usually highly aberrant. All three wheat x maize combinations were karyotypically unstable and rapidly eliminated maize chromosomes to produce haploid wheat embryos.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00262508
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  • 6
    Digitale Medien
    Digitale Medien
    The production of haploid wheat plants from wheat x maize crosses (1988)
    Springer
    Theoretical and applied genetics 76 (1988), S. 393-397 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Wheat ; Maize ; Wide-crosses ; Embryo culture ; Haploids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Hybrid embryos from hexaploid wheat x maize crosses rapidly lose the maize chromosomes to produce haploid wheat embryos. Such embryos almost always aborted when left to develop on the plant, and only 1 was recovered from 2440 florets (0.17% of the expected number). Embryos had greater viability in spikelet culture, 47 (26.5% of the expected number) being recovered from 706 ovaries. Thirty-two of these embryos germinated to give green plants, 31 of which were haploid (21 wheat chromosomes) and 1 of which was euploid (42 wheat chromosomes). Spikelet culture enabled 17.1% of the expected number of embryos to be recovered as haploid plants, a 100-fold improvement on allowing embryos to develop in vivo. Ten haploid plants of ‘Chinese Spring’ (kr1, kr2), 13 plants of ‘Chinese Spring (Hope 5A)’ (kr1, Kr2), and 8 of ‘Hope’ (Kr1, Kr2) were recovered. The potential of wheat x maize crosses for wheat haploid production and for gene transfer from maize to wheat is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265339
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