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  • 1
    Electronic Resource
    Electronic Resource
    Effect of microgravity on the cell cycle in the lentil root (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 105 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Characteristics of the cell cycle in cortical regions (0–0.6 mm from the root-cap junction) of the primary root of lentil (Lens culinaris L.) during germination in the vertical position on earth were determined by iododeoxyuridine labelling and image analysis. All cells were in the G1 phase at the beginning of germination and the duration of the first cell cycle was about 25 h. At 29 h, around 14% of the cortical nuclei were still in the G2 or M phases of the first cell cycle, whereas 53 and 33% of the nuclei were respectively in the G1 or S phase of the second cell cycle. In parallel, the cell cycle was analysed in root tips of lentil seedlings grown in space during the IML 2 mission (1994), (1) on the 1-g centrifuge for 29 h, (2) on the 1-g centrifuge for 25 h and placed in microgravity for 4 h, (3) in microgravity for 29 h, (4) in microgravity for 25 h and placed on the 1-g centrifuge for 4 h. The densitometric analysis of nuclear DNA content showed that in microgravity there were less cells in DNA synthesis and more cells in G1 than in the controls on the 1-g centrifuge (flight and ground). The comparison of the sample grown continuously on the 1-g centrifuge in space and of the sample grown first in 1-g and then in microgravity indicated that 4 h of microgravity modified cell cycle, increasing the percentage of cells in the G1 phase. On the contrary, the transfer from microgravity to the 1-g centrifuge (for 4 h) did not provoke any significant change in the distribution of the nuclear DNA content. Thus the effect of microgravity could not be reversed by a 4 h centrifugation. As the duration of the first cell cycle in the lentil root meristem is about 25 h, the results obtained are in agreement with the hypothesis that the first cell cycle and/or the second G1 phase was lengthened in absence of gravity. The difference observed in the distribution of the nuclear DNA content in the two controls could be due to the fact that the 1g control on board was subjected to a period of 15 min of microgravity for photography 25 h after the hydration of the seeds, which indicated an effect of short exposure to weightlessness. The mitotic index of cortical cells was greater on the 1-g centrifuge in space than in any other sample (flight and ground) which could show an effect of the centrifugation on the mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.105125.x
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  • 2
    Electronic Resource
    Electronic Resource
    Microspectrophotometric measurements of DNA by automated computerized scanning in cycling cells of theChrysanthemum segetum shoot apex (1987)
    Springer
    Protoplasma 136 (1987), S. 183-190 
    Details
    ISSN: 1615-6102
    Keywords: Chrysanthemum segetum ; DNA condensation/decondensation ; DNA scanning microdensitometry ; Shoot apex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new technique of exploitation of the data was proposed after DNA scanning microdensitometry. By using all of the measurements obtained from the seriated sections of a single nucleus, this method made it possible to estimate six characteristic parameters during the different phases of the cell cycle in the various shoot apical cells. The cells whose rate of proliferation was the highest showed the biggest variations of their nuclear and nucleolar volumes during the cell cycle. In the axial zone, where the cells have a slow cell cycle and display the longest duration of the G1 phase, the volume occupied by dispersed DNA was greater than in the cells of the lateral zone and of the rib meristem, where the cell cycle and the G1 phase were short. No matter what the cell type, the proportion of the dispersed and condensed DNA varied little when the G1 and G2 phases were compared. In the Z phase, characterized by a decondensation of the DNA, the mean DNA amount was 3.4 C. The evolution of the nuclear density during the interphase was also estimated. It is demonstrated that the main feature of the shoot apex zonation was the decondensation of the condensed DNA in the axial zone in both the G1 and G2 phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276367
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  • 3
    Electronic Resource
    Electronic Resource
    Rates of cell division in the young prefloral shoot apex ofChrysanthemum segetum L. (1987)
    Springer
    Protoplasma 138 (1987), S. 156-160 
    Details
    ISSN: 1615-6102
    Keywords: Cell cycle duration ; Chrysanthemum segetum ; Prefloral phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The rate of cell division was determined by the colchicine induced metaphase-accumulation technique in the young prefloral shoot apex of the quantitative long-day plantChrysanthemum segetum L. growing under conditions favourable to flowering (16-hour photoperiod; 124μEm−2s−1; 22 °C). Cell cycle duration was evaluated in relation to the location of the cells in the intact apex. The cell cycle durations were 53.5 hours, 47.4 hours, and 97.7 hours in the axial, lateral and subapical central cells respectively. Compared with previous results, these data give evidence of the major role played by the early increase in cell division rate of axial cells in the new pattern of the prefloral shoot apex at its initial stage of development. By comparison with the vegetative shoot apex, the cell cycle duration was preferentially shortened in the axial zone; it was only slightly altered in the lateral zone while it was lengthened in the vacuolating subapical central cells. In the three zones within the prefloral shoot apex, the duration of mitosis was constant (3.2 to 3.3 hours) and the same as in the vegetative shoot apex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281024
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  • 4
    Electronic Resource
    Electronic Resource
    Ageing of theSilene coeli-rosa L. shoot apex under non-inductive conditions: Changes in morphology, mitotic index, and polypeptide composition (1989)
    Springer
    Protoplasma 153 (1989), S. 30-36 
    Details
    ISSN: 1615-6102
    Keywords: Ageing ; Non-inductive conditions ; Shoot apical development ; Silene coeli-rosa ; Two-dimensionalmini-gel electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ageing was studied in the shoot apex of the long day plant,Silene coeli-rosa by maintaining it in non-inductive short day conditions for 170 days. The dimensions, the zonation, and the polypeptidic pattern of the shoot apex, and the rate of leaf initiation were altered in 170-day-old plants compared with young plants grown under the same conditions (28 days). In aged plants, the number of cells increased in all shoot apical zones and, notably, the mitotic index increased in the axial zone; however, the rate of leaf initiation slowed down. These changes showed some similarities to those during the intermediate phase in quantitative photoperiodic species. The two-dimensional mini-gel electrophoretic study of protein extracts from shoot apices of young and ageing plants maintained in non-inductive conditions revealed 489 common polypeptidic spots, 13 unique to the young state and 24 new ones specific to aged plants. The spots characteristic for each state represented only 3.6% of the total identified polypeptides, but apical development under non-inductive conditions was characterized by qualitative changes in the polypeptide complement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322462
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  • 5
    Electronic Resource
    Electronic Resource
    Electron microscopy and X-ray microanalysis as tools for fine localization of the β-glucuronidase activity in transgenic plants harbouring the GUS reporter gene (1992)
    Springer
    Protoplasma 170 (1992), S. 68-76 
    Details
    ISSN: 1615-6102
    Keywords: β-Glucuronidase ; Cytoenzymology ; CaMV 35S-GUS ; Transgenic tobacco ; X-ray microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The GUS reporter gene encoding β-glucuronidase is very useful in various domains of plant genetic engineering. A method for ultrastructural detection of its activity was developed using 35S-GUS transgenic tobacco root tips. Short glutaraldehyde prefixation at 4°C preserved up to 70% enzyme activity and was followed by brief incubation in X-Glu, strong postfixations, then quick dehydration at low temperature before resin embedding. In these conditions, transgenic cells were well preserved and displayed electron dense indigo precipitates with a crystalline structure as shown by electron diffraction. Due to other dense structures in the tissues, controls of the nature of the reaction product (diX-indigo) were necessary. A first control was carried out by means of X-ray microanalysis in order to check the presence of bromine. Other controls, including incubated non-transformed tissues, non-incubated or boiled transgenic roots as well as transgenic samples incubated with the specific β-glucuronidase inhibitor, D-saccharic acid-1,4-lactone, were also carried out. The discussion points out the potential uses but also the limits of the method, non-specific localizations of the diX-indigo microcrystals being possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384458
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