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  • 11
    Electronic Resource
    Electronic Resource
    Early post-pollination events in hexaploid wheat × maize crosses (1990)
    Springer
    Sexual plant reproduction 3 (1990), S. 70-76 
    Details
    ISSN: 1432-2145
    Keywords: Wheat ; Maize ; Hybridization ; Fertilization ; Karyogamy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytological events in the first 12 h after pollination were studied in crosses between the hexaploid wheat genotype Chinese Spring and the maize genotype Seneca 60. A pollen tube was first observed in the embryo sac 4 h after pollination, and maize sperm nuclei were first observed in the embryo sac after 5 h. On 29 occasions two, and on 1 occasion three, pollen tubes penetrated the embryo sac. Four categories of aberration limiting the frequency of fertilization were identified: (1) in 20% of florets no pollen tube reached the embryo sac; (2) in at least 1.9% the pollen tube severely damaged the wheat egg cell and polar nuclei; (3) in 33% the maize sperm nuclei were not released from the pollen tube; and (4) in 16% the sperm nuclei were released into the embryo sac but failed to move to either of the wheat gametes. In the remaining 29% sperm nuclei were more often found in the egg cell than at the polar nuclei. The results suggest that karyogamy occurs with very high efficiency when a sperm nucleus reaches the egg cell, but with only about 50% efficiency when a sperm nucleus reaches the polar nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189954
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  • 12
    Electronic Resource
    Electronic Resource
    The use of genomic in situ hybridization (GISH) to show transmission of recombinant chromosomes by a partially fertile bigeneric hybrid, Gasteria lutzii ×Aloe aristata (Aloaceae), to its progeny (1997)
    Springer
    Chromosoma 105 (1997), S. 342-348 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Genomic in situ hybridization (GISH) was used to study somatic chromosomes of parental and progeny plants (all 2n=2x=14) of the bigeneric hybrid between Gasteria lutzii and Aloe aristata (Aloaceae), which is partially fertile, a rare occurrence in plants. GISH successfully distinguished between the two parental genomes in the F1 hybrid and revealed numerous genomic recombinations in chromosomes transmitted by the F1 to the back-cross progeny. The results indicate high levels of meiotic compatibility between the parental genomes, even though they differ in size by 20%. Recombination occurred at a frequency that was higher than that expected from the analysis of orcein-stained meiosis in the F1. The discrepancy suggests that terminalization may occur prior to or during metaphase I, reducing the apparent chiasma frequency, or possibly reveals an under-estimation caused by difficulties in resolving closely grouped chiasmata by eye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050193
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  • 13
    Electronic Resource
    Electronic Resource
    Aloe L. – a second plant family without (TTTAGGG)n telomeres (2000)
    Springer
    Chromosoma 109 (2000), S. 201-205 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The physical ends of chromosomes are protected and stabilised by telomeres. The sequence of telomeric DNA normally consists of a simple repeating unit that is conserved in many organisms. Most plants examined have been shown to possess Arabidopsis-type telomeres consisting of many repeat copies of the sequence 5′-TTTAGGG-3′. Using fluorescent in situ hybridisation, slot blotting and the asymmetric polymerase chain reaction we demonstrate an absence of Arabidopsis-type telomeres in the genus Aloe (family Asphodelaceae). The only other plant genera so far reported without such telomeres are Allium, Nothoscordum, and Tulbaghia (family Alliaceae). As these genera and Aloe are petaloid monocots in the Asparagales, it is suggested that an absence of Arabidopsis-type telomeres may be characteristic of this related group of plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050429
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  • 14
    Electronic Resource
    Electronic Resource
    Induced and developmental variation in chromosomes of meristematic cells (1969)
    Springer
    Chromosoma 27 (1969), S. 226-244 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Change in chromosome size in root tip meristems of rye and Allium cepa are induced by growing the plants in solutions differing in phosphorus content. The chromosomes are 50% larger by volume in a “high” phosphate as compared with a “no” phosphate solution. Alteration of other elements supplied in culture also induces change in the size of chromosomes. — The size variation is a reflection of change in the chromosome dry mass. In part at least this change in mass is attributable to alteration in the amount of protein. The DNA component of the chromosomes remains unchanged. — A consistent pattern of change in chromosome size, quite independent of that induced by varying the culture solution, is related to age and development. For example, the root tip chromosomes double in size during the first three weeks of growth in rye seedlings. Thereafter the size decreases. As with the induced chromosome changes the protein content alters, the DNA amount remains constant. — Variation in the “non-permanent” component of the chromosomes in meristems appears to be closely correlated with the rate of cell metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326147
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  • 15
    Electronic Resource
    Electronic Resource
    The time rate and mechanism of chromosome elimination in Hordeum hybrids (1976)
    Springer
    Chromosoma 54 (1976), S. 175-200 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Seed development at 20±1° C in continuous light was studied during the first 5 days after pollination in diploid Hordeum vulgare, diploid H. bulbosum and the cross, H. vulgare x H. bulbosum, where H. bulbosum chromosomes were eliminated. Developing seeds were fixed and stained at known intervals after pollination and the embryo sac contents dissected out for cytological examination. — In all cases, the pattern of development was similar to that previously described for the Triticeae. After intraspecific pollination, the rate of endosperm and embryo development was significantly faster in H. vulgare than in H. bulbosum. In hybrid tissues, the rate was intermediate, but often much nearer to that of H. vulgare at first. Elimination of H. bulbosum chromosomes occurred only during endosperm and embryo mitoses. Usually, 0–3 chromosomes were lost at any one division but up to 7 were lost at some. Elimination, which occurred as early as zygotic anaphase, was nearly or quite complete in all dividing cells in both embryo and endosperm after 5 days. The mean number of chromosomes lost per nucleus per nuclear cycle was low at first but rose rapidly and stayed high for about a day in each tissue before falling quickly. The rate of elimination in each tissue was maximal when that tissue first synthesized significant amounts of new cytoplasm (day 2 after pollination in the endosperm and day 3 in the embryo). At mitosis, chromosomes being eliminated differed from others only in failing to congress at metaphase or to reach a pole at anaphase or both. — It is noted that in several widely different examples where either haploids are produced when only hybrids are expected, or where chromosomes of one species are preferentially eliminated from hybrid cells, nucleolar activity was suppressed in chromosomes of the genome which was selectively or preferentially eliminated. Consequently, it is suggested that chromosome elimination in Hordeum hybrids may be caused by a disturbed control of protein metablism in hybrid seeds and perhaps H. bulbosum chromosomes are selectively eliminated because they are less efficient than H. vulgare chromosomes at forming normal attachments to spindle protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292839
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  • 16
    Electronic Resource
    Electronic Resource
    Variation in nuclear DNA in the genus Secale (1977)
    Springer
    Chromosoma 61 (1977), S. 149-176 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Estimates of the 4C DNA amount per nucleus in 16 taxa of the genus Secale made by Feulgen microdensitometry ranged from 28.85 picograms (pg) in S. silvestre PBI R52 to 34.58 pg in S. vavilovii UM 2D49, compared with 33.14 pg in S. cereale cv. “Petkus Spring” which was used as a standard. Giemsa C-banding patterns showed considerable interspecific and intraspecific variation and several instances of polymorphism for large telomeric C-bands. The proportion of telomeric heterochromatin in the genome ranged from about 6% in S. silvestre and S. africanum to about 12% in cultivated rye. A detailed comparison of nine taxa showed no overall relationship between 4C DNA amount and the proportion of telomeric heterochromatin in the genome. However, evidence is presented which strongly supports the notion that the major evolutionary change in chromosome structure in Secale has involved the addition of heterochromatin at, or close to, the telomeres. It is suggested that saltatory amplification events at telomeres were initially responsible for each large increase in DNA amount. Subsequently unequal crossing over between homologues may have played an important secondary role by extending the range of variation in the amount of heterochromatin at a given telomere, while crossing over between non-homologues may have provided a useful mechanism allowing an increase in the DNA amount at one telomere to be distributed between chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327398
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  • 17
    Electronic Resource
    Electronic Resource
    Cytological investigations of the effect of colchicine on meiosis in Lilium hybrid cv. “Black Beauty” microsporocytes (1979)
    Springer
    Chromosoma 72 (1979), S. 157-173 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using colchicine, two methods have been successfully applied for the induction of tetraploid meiocytes at premeiotic mitosis in the near achiasmate diploid hybrid cultivar “Black Beauty” of Lilium. The experiments were aimed at understanding whether the achiasmate condition is attributable to insufficient homology for effective pairing or to some genie defect in order to interpret the data obtained from molecular studies. Cytological observations demonstrate a strong correlation between the induction of tetraploidy and subsequent chiasma formation. The chiasma frequency per cell in untreated diploid control meiocytes ranged from 0 to 8 (mean 2.25), while in colchicine treated undoubled cells sampled 14±2 days after the start of treatment it ranged from 0 to 2 (mean 0.148). By comparison, the chiasma frequency per cell in colchicine-doubled tetraploid cells ranged from 29 to 51 (mean 42.24), such cells showing complete or near complete bivalent pairing. These results, similar to those reported previously for other higher plant species, demonstrate that the achiasmatic condition in “Black Beauty” is not due to a genie defect. The methods developed have made possible hitherto inaccessible biochemical analyses of meiocytes that had been treated with colchicine or other chemicals at premeiotic stages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293232
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  • 18
    Electronic Resource
    Electronic Resource
    Regulation of R-protein and endonuclease activities in meiocytes by homologous chromosome pairing (1979)
    Springer
    Chromosoma 72 (1979), S. 191-201 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Achiasmate meiocytes of Lilium cv. Black Beauty do not undergo DNA nicking at pachytene, nor do they acquire the high level of R-protein during zygotene-pachytene that is characteristic of chiasmate types. Induction of tetraploidy in such meiocytes with its accompanying increase in chiasma frequency results in a pachytene nicking pattern that is indistinguishable from what occurs in chiasmate plants. R-protein also increases to a level that on a per diploid genome basis is at least as high, and probably higher, than the level of chiasmate diploids. The absence of nicking in the achiasmate diploid is not due to a lack of appropriate enzyme activity but seems to result from the fact that unpaired or ineffectively paired chromosome regions are not accessible to the enzyme. The regulation of R-protein level by homologous pairing is examined but remains poorly understood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293234
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  • 19
    Electronic Resource
    Electronic Resource
    The effect of colchicine on meiosis in Lilium speciosum cv. “Rosemede” (1979)
    Springer
    Chromosoma 72 (1979), S. 175-189 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Chromosome pairing and chiasma frequency were studied in meiocytes at diakinesis of Lilium speciosum cv. “Rosemede” fixed up to 21 days after the start of either continuous or 3 day pulse colchicine treatment. The two treatments gave similar results. In pulse treated pollen mother cells (PMCs) the mean chiasma frequency per cell fell from 26.4 in controls to 8.5 after fourteen days while the mean number of univalents per cell increased from 0.05 to 17.58. There was a negative correlation between mean chiasma frequency per bivalent and per PMC in colchicine treated buds; univalents were preferentially induced in bivalents with one chiasma, and preferentially excluded in bivalents with 4 chiasmata. Some chiasmata were redistributed to surviving bivalents despite the concurrent reduction in chiasma frequency per meiocyte. — Colchicine sensitivity began in premeiotic interphase and extended to mid or late zygotene in PMCs; ongoing synapsis was unaffected. However, susceptibility to univalency was asynchronous between bivalents occurring at zygotene in short chromosomes but at late premeiotic interphase in the longest chromosomes. The number of chiasmata per bivalent could be altered by colchicine without inducing univalents, but the ultimate effect was to reduce the number of chiasmata per bivalent (or per chromosome arm) directly to zero. The major factors determining the order and extent of reduced pairing and chiasma number were total chromosome length and arm length. Pairing and chiasma formation in embryo sac mother cells were less sensitive to colchicine than in PMCs, but their behavior was otherwise similar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293233
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  • 20
    Electronic Resource
    Electronic Resource
    Somatic deletion and redistribution of telomeric heterochromatin in the genus Secale and in Triticale (1983)
    Springer
    Chromosoma 88 (1983), S. 293-298 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract C-banding analysis of populations of Secale kuprijanovii L., S. cereale L., and x Triticosecale Wittmack established that Secale chromosomes that were modified by the loss of a telomeric C-band arose spontaneously by breakage in somatic tissue and could be stabilized and maintained over at least two generations. In S. cereale approximately double-sized C-bands were seen on every arm that originally contained a C-band except 1RS, 2RS, 3RS, and 7RS. One plant was homomorphic for an amplified band on 3RL which was stable over two generations. In the tetraploid triticale analyzed, an amplified telomeric C-band was found on 5RS and was stable in the homomorphic condition for two generations. Even though Secale chromosomes with deleted or amplified telomeric C-bands can arise spontaneously in the somatic and germ tissue of Secale species and triticale, they are not common. The conditions required for their formation and stabilization within a population are not known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292906
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