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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of homologous polytene chromosomes in Phaseolus coccineus embryo suspensor cells: morphological, autoradiographic and cytophotometric analyses (1982)
    Springer
    Chromosoma 86 (1982), S. 383-396 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The functional behaviour of unpaired homologous polytene chromosomes (2n=22), was investigated in nuclei of Phaseolus coccineus embryo suspensor cells. Observations were carried out on the morphological level and after 3H-thymidine and 3H-uridine autoradiography. Histone and total protein contents in the chromatin were also investigated. It was shown that corresponding regions of homologous chromosomes may show different functional structures. 3H-thymidine incorporation demonstrated differences between homologues in both DNA synthesis leading to chromosome endoreduplication (polytenization) and DNA amplification (extra DNA synthesis). 3H-uridine autoradiography showed that homologous regions in a given chromosome pair may display three labeling patterns: i) both regions labeled; ii) both regions unlabeled; iii) one region labeled and the other unlabeled. These three states are found to occur in different cells of one and the same embryo suspensor. Differences between homologous chromosome regions were also found in the ratios between DNA and protein contents in their chromatin. These results, which show that the functional activity of homologous chromosomes of the same complement may greatly differ, are discussed in relation to the characteristics of the system investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292265
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of light and gibberellic acid on coleoptile and first-foliage-leaf growth in durum wheat (Triticum durum Desf.) (1984)
    Springer
    Planta 160 (1984), S. 298-304 
    Details
    ISSN: 1432-2048
    Keywords: Blue light ; Coleoptile growth ; Elongation growth (GA, light) ; Gibberellin and light ; Leaf growth ; Light, gibberellin and growth ; Triticum (GA, light)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparison has been made of the relative effectiveness of light quality and quantity and gibberellic acid (GA3) treatment on the elongation growth of the coleoptile and the first foliage leaf in durum wheat (Triticum durum Desf. cvs. Cappelli and Creso). The cultivar Creso is a shortstrawed variety carrying the Gai 1 gene on chromosome 4A, which influences both plant height and insensitivity to applied gibberellins. The main conclusions are as follows: 1) coleoptile elongation growth appears to be modulated via the fluencerate-dependent action of a blue-light receptor and via a low energy response of phytochrome; 2) the inhibition of first-foliage-leaf growth depends on the operation of a single blue-light-responsive photoreceptor; 3) high energy blue light produces the same inhibitory effect on the two wheat cultivars, whereas at relatively low fluences of white and blue light, the cultivar Creso is more sensitive; 4) the insensitivity to applied GA3 exerted by the gene Gai 1 in Creso is independent of light; 5) in Cappelli, the action of light on coleoptiles appears to be independent of the applied GA3, whereas the hormone is able to change the pattern of growth inhibition of the first-foliage-leaf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393410
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  • 3
    Electronic Resource
    Electronic Resource
    Different structure of polytene chromosome ofPhaseolus coccineus suspensors during early embryogenesis 3. Chromosome pair VI (1984)
    Springer
    Protoplasma 122 (1984), S. 98-107 
    Details
    ISSN: 1615-6102
    Keywords: DNA puffs ; RNA puffs ; Polytene chromosomes ; Labeling pattern ; Satellite DNA ; Highly repeated DNA sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different regions of polytene chromosomes pair VI have been characterized by: 1. morphological observations, 2. incorporation of3H-thymidine and3H-uridine, 3. cytophotometry of DNA and associated proteins, 4. hybridization with satellite DNA and highly repeated DNA sequences. The collected data indicate that DNA and RNA puffs are organized by heterochromatic segments. DNA puffs show often a clustered pattern of labeling by3H-thymidine and RNA puffs are always labeled by3H-uridine. Each heterochromatic segment is characterized by a definite ratio between DNA and associated fast-green stainable proteins. Satellite DNA binds mostly to heterochromatic blocks at centromere, highly repeated DNA sequences bind, with approximately the same frequency, to centromeric heterochromatin and to the main intercalary heterochromatic band. The telomeric portions of euchromatin seem to be also enriched in highly repeated DNA sequences. The results indicate that heterochromatic chromosome segments might be sites of intense localized DNA replication. The same chromosome regions are also engaged in an active transcription process. The response to hybridization suggests that heterochromatic blocks of chromosome pair VI are heterogeneous in nucleotide sequences. The present studies also indicate that DNA and RNA puffs organized by different chromosome sites are specific of particular steps of embryo differentiation. The observed metabolic aspects of the suspensors's polytene chromosomes are discussed in relation to the synthesis of growth regulators which is known to occur in the suspensor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279442
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  • 4
    Electronic Resource
    Electronic Resource
    Diploidy and chromosome endoreduplication in the development of epidermal cell lines in the first foliage leaf of durum wheat (Triticum durum Desf.) (1983)
    Springer
    Protoplasma 118 (1983), S. 36-43 
    Details
    ISSN: 1615-6102
    Keywords: Chromosome endoreduplication ; Diploidy ; Durum wheat ; Leaf epidermis ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of epidermal cell lines in the first foliage leaf ofTriticum durum was studied with a combined cytological and DNA cytophotometric analysis. It was shown that: (1) At emergence, the distal portion of the leaf is made of the cells pre-existing in the embryonic leaf and the mitotic activity is localized at the base of the leaf lamina (basal meristem). (2) The proliferating protoderm (outermost cell layer of the basal meristem) contains a meristematic cell population and a differentiating cell population. The cells produced by the protoderm differentiate with 2C, 4C, 8C, and 16 C nuclear DNA contents. (3) The endoreduplicated cells (EC) together with 4C cells form prominent cell rows in the leaf epidermis. The interstomatal cells (ISC) are all 2 C and the inter-hairs cells (IHC) are mostly 2 C (rare 4 C cells lie adjacent to the EC). (4) In the fully developed leaf, the frequency distribution of EC (8 C and 16 C) and 4C cells in a given epidermal segment (Fig. 1) corresponds to the frequency established in the epidermis differentiation zone (zone b, segment 1) at the time of development of that segment:e.g., segment 6 developed at 1–2 days after seed germination, segment 5 at 3 days after germination and so on. (5) Epidermal cell elongation starts in segment 1 and reachs its maximum in the older leaf segments, 5 and 6. The rate of cell elongation is independent of nuclear DNA content; chromosome endoreduplication precedes elongation. (6) The possibility of using epidermal cell parameters in studies on first leaf growth inT. durum is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284744
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  • 5
    Electronic Resource
    Electronic Resource
    Location of heitz's zerstäubungsstadium (dispersion phase) in the mitotic cycle ofPhaseolus coccineus and the concept of Angiosperm endomitosis (1981)
    Springer
    Protoplasma 109 (1981), S. 403-414 
    Details
    ISSN: 1615-6102
    Keywords: Angiosperm endomitosis ; Dispersion phase ; Mitotic cycle ; Phaseolus coccineus ; Zerstäubungsstadium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary DNA microdensitometry and autoradiography after treatment with3H-thymidine were used to study the phase of dispersion of chromocenters (Z phase) in parallel with chromocentric nuclei inPhaseolus coccineus. In all materials studied, two types of chromocentric nuclei were present. In radicle apices of dry seeds, two classes of nuclear DNA contents were measured, 2 C (G1) and 4 C (G2). The 2 C DNA class comprised all chromocentric type I nuclei, the 4 C class included Z phases and chromocentric type II nuclei. The 4 C (G2) condition of Z phases implies that Z phases maintain their nuclear structure for some time after the end of DNA replication. Shoot apices also contain 2 C (G1) and 4 C (G2) nuclei but 4 C nuclei (Z phases and chromocentric type II nuclei) are rare. In seedling root apices, Z phases are from 1.02 to 4.08 times as frequent as prophases. This excludes that Z phase is a very early prophase. DNA microdensitometry shows that the chromocentric type I includes 2 C (G1) nuclei and nuclei in the first part of the S phase, Z phases include 4 C (G2) nuclei and nuclei in the last stage of the S phase and chromocentric type II includes mainly 4 C (G2) nuclei and nuclei in the second part of S. After 90 minutes of treatment with3H-thymidine all Z phase nuclei are labeled. This result and the microdensitometric data unequivocally demonstrate that Z phase is located at the end of S. The present results and those of previous authors on Z phase are discussed in relation to Geitler's concept of Angiosperm endomitosis. It is concluded that the term “Angiosperm endomitosis” must be abandoned and substituted by the term “chromosome endoreduplication”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01287455
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