Accessory nucleoli in microsporocytes of hybrid Phlox

Levin, Donald A.

doi:10.1007/bf00396499

Cited by 7 publications

(8 citation statements)

References 28 publications

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“…In C. agatiflora, however, the nucleoli which exceed in number that of secondary constrictions, do not fuse untill they individually disappear at the end of prophase I as normally happens in other organisms except in Euglena and Spirogyra (Cohn, 1969). The failure of fusion has also been observed in the Phlox pilosa complex (Levin, 1973) and to lesser a extent in Oxalis dispar (Marks, 1957).…”

Section: Studies Of Male Meiosis In About 55 Species Ofmentioning

confidence: 79%

“…In Oxalis dispar (2n=12) 1-10 nucleoli are present in a cell although there is no specific nucleolar organizer (Marks, 1957). Similarly in the Phlox pilosa complex 1-5 nucleoli are present against two nucleolar chromosomes in the somatic complement (Levin, 1973). In C. agatiflora (2n=!6) as in most other diploid species of Crotalaria, the mitotic complement contains two nucleolar chromosomes (Raina & Verma, 1979;unpublished) and wherever male meiosis has been analysed, all but C. agatiflora have usually one nucleolus in premetaphase-I cells.…”

Section: Studies Of Male Meiosis In About 55 Species Ofmentioning

confidence: 99%

“…In C. agat(/tora it is presumed that due to a change in the cell caused by hybridity, some latent organizers get activated and synthesize nucleoli of varying sizes depending upon the quantum of repetitive rDNA present in them, although hybridity is not involved in the presence of latent organizers as such. The dispersion of part of the nucleolar organizer in the genome might have occurred due to spontaneous breakage across the organizer(s) in the distant past (Levin, 1973). Normally they remain latent and only in some changed physical and/or genetic environment they might get activated (Jain, 1957;Snoad, 1956;Levin, 1973).…”

Section: Agatiflora Growing Wild In Ethiopia and Eastmentioning

confidence: 99%

“…The dispersion of part of the nucleolar organizer in the genome might have occurred due to spontaneous breakage across the organizer(s) in the distant past (Levin, 1973). Normally they remain latent and only in some changed physical and/or genetic environment they might get activated (Jain, 1957;Snoad, 1956;Levin, 1973). Often in species hybrids and allopolyploids the normal organizer of one of the species involved, is suppressed (Navashin, 1927(Navashin, , 1934Keep, 1962Keep, , 1971Yeh& Peloquin, 1965).…”

Section: Agatiflora Growing Wild In Ethiopia and Eastmentioning

confidence: 99%

“…In size, they may account for about one third of the nuclear volume or may be hardly discernable in the nucleus. In the majority of plant and animal cells one nucleolus is present in each genome (Sybenga, 1972) and more than one have been reported in only few (Cohn, 1969;Fischberg & Wallace, 1960;Beermann, 1960;Marks, 1957;Darvey & Driscoll, 1972;Chakravorti, 1960;Levin, 1973;Heitz, 1931). During the analysis of male meiosis in 35 species of Crotalaria L. (Leguminosae), one species, C. agatiflora Schweinf., was found to have consistently more than one nucleolus in some PMCs.…”

Section: Introductionmentioning

confidence: 99%

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Cytogenetics of Crotalaria V. Supernumerary nucleoli in C. agatiflora (Leguminosae)

Verma

Raina

1981

Genetica

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Of 35 species of Crotalaria (Leguminosae) studied, all but one had usually one nucleolus in the premetaphase I cells. In C. agatiflora 300 PMCs from four out of five plants were investigated and the percentage cells with more than one nucleolus was determined as well as the nature of nucleolar attachment to bivalents and the range and the sizes of various nucleoli present in the cell. The "aberrant' cells ranged from 42 to 50%. The nucleoli (1-6) were usually attached to different bivalents. Where one nucleolus was present in the cell, it was always attached to an X-shaped bivalent, formed of a pair of nucleolar chromosomes. In the aberrant cells one nucleolus usually was attached to such a bivalent. The presence of accessory nucleoli has been attributed to hybridity as a result of large-scale intercrossing among five subspecies and consequent dispersal of intermediates in the adjoining areas where C. agatflora grows wild (East Africa and Ethiopia).The change in the regulatory system of the cell caused by hybridity results in activation of latent nucleolar organizers, although their overall presence in the genome is not due to hybridity.

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Section: Studies Of Male Meiosis In About 55 Species Ofmentioning

confidence: 79%