Untersuchungen �ber Die Cytologie polyploider Pflanzen II

Linnert, Gertrud

doi:10.1007/bf00319485

Cited by 24 publications

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“…However, only recently attempts have been made (Linnert 1949, Peters 1954, Gottschalk 1955 to look for interchromosomal relationships in prophase stages of meiosis, which might correspond to secondary association.…”

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“…2-7) lend themselves to two interpretations which are not necessarily mutually exclusive: 1) a fusion of the non-homologous chromosomes E and G at the centromeres similar to that reported in Zea mays (McClintock 1933); (see interpretive diagrams: figs. 18-22) 2) an exchange of portions of pairing strands involing the long arm of chromosome E and the short arm of chro mosome G; (see also Linnert 1949;Peters 1954;Gottschalk 1955 The assumption of such a stretching effect becomes more questionable when attempting to explain the cross-shaped configurations of figures 5, 6 and 7; (see also figs. 21 and 22).…”

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Secondary Association in the Castor Oil Plant

Jakob

1957

CYTOLOGIA

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A study of pollen mother cells of the castor oil plant (Ricinus communis L.; 2n=20) at diakinesis and metaphase I (MI) of meiosis reveals associations of more than two chromosomes.These consist of groups of presumably non-homologous bivalents associated in various degrees of intimacy. Thus one may observe loose side by side associations of pairs as well as apparent configurations of four chromosomes reminiscent of quadrivalents or translo cations; (figs. 11-15). Richharia (1937) and Kurita (1946) have reported secondary association in Ricinus at metaphase I and later stages of meiosis. The general phe nomenon of secondary association was first observed by Kuwada (1910) in Oryza sativa. Darlington (1928) and Lawrence (1931) were the first to re late this phenomenon of side by side association of bivalents in groups of two, three or more, to the homology existing between these bivalents. Primary pairing at zygotene and chiasma formation between more than two homolog ous chromosomes were known to result in multivalents. This type of pairing was considered as distinct from secondary pairing (or association) in which there is only a loose association of bivalents without chiasmata connecting them. According to these authors this association between pairs starts only at prometaphase and metaphase I and continues into the later meiotic stages. They suggested that chromosomes which have secondary association are homolog ous or partially so, and reflect the polyploid origin of the species exhibiting this phenomenon.More recently Brown (1950) has shown that in Luzula, secondary as sociation at metaphase I is an artifact of the squash technique. Stebbins (1950) recognizes that secondary association serves in many cases as an in dication of the polyploid origin of a species or genus, but he cautions against elaborate phylogenetic conclusions based on such evidence.Chromosome homology has been presumed to be the basic element com mon to both primary and secondary association (Lawrence 1931). However, only recently attempts have been made (Linnert 1949, Peters 1954, Gottschalk 1955 to look for interchromosomal relationships in prophase stages of meiosis, which might correspond to secondary association.

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Secondary Association in the Castor Oil Plant

Jakob

1957

CYTOLOGIA

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“…Es besteht aber vielleiclit die Miiglichkeil, dass es eine Reihc gradueller Unterschiede gibt, die voii einer festen Verbindung z u ciner nur durcli die rauiiiliche Lage nngedeuteten Bezieliung reiclien. (Vgl LINNERT, 1949)…”

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