摘要:

The nucleolar secondary constrictions ofVicia fabachromosomes were filled with a weakly stained substance when the sections were treated with conventional double staining and examined under an electron microscope. But both silver staining and ribonucleoprotein preferential staining contrasted these constrictions as positively stained areas. On the other hand, the nucleolus-associated chromatin blocks in the epidermal cells were clearly impregnated with silver although they were fully condensed, suggesting that ribosomal (r) RNA genes are organized into the condensed chromosomal segment when cells differentiate into specialized cells such as the epidermal cells.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797225

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

The karyotype and meiosis of wild and cultivated ulluco were analysed. All wild ulluco clones studied were triploids, 2n= 36, and all cultivated ones diploids, 2n= 24. A tetraploid cell line, 2n= 48 was found in a cultivated clone. Cultivated and wild ulluco have a similar set of chromosomes, with two pair of long, two pair of short and eight pair of intermediate chromosomes, and with two pair of satellite chromosomes. This indicates that the basic chromosome number of ulluco may bex= 6. Male and probably also female meiosis of diploid cultivated ulluco is regular and pollen stainability high. Reasons for the poor seed set of cultivated ulluco are to be looked for in other processes than meiosis. Meiosis of triploid wild ulluco is irregular, leading predominantly to aneuploid gametes, pollen stainability was low, and there was more variation in pollen size than in cultivated ulluco, most probably because of aneuploidy.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797226

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

Secale cerealeproduces, in the same ear, brown and black caryopses, which differ widely in size and morphology. These phenotypic differences are correlated to different variations in both germination and viability during seeds lifespan. Spontaneous mutagenesis analysis demonstrates that the two kinds of seeds display a different nuclear damage during storage. The brown caryopses are less damaged during the dormancy period, but more damaged during aging, mainly in the last months of life. This different pattern of dormancy and aging in seeds produced within the same ear might be of significance for specie propagation and safeguard.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797227

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

Meiotic pairing of the B chromosomes of rye in the genetic environment of wheat was studied in order to investigate the effect of some structurally altered derivatives of B chromosomes on the pairing of the standard B chromosomes in the plant series containing 42 wheat chromosomes plus 2stBs + 1defB, 3stBs + 1defB, 3stB+ lsB, 3stBs+ 1siB, 3stBs+11iB, 3stBs + 2mBs, 4stBs + 1siB, 4stBs+11iB, 5stBs + 1siB, and 6stBs + 1siB chromosomes, and a comparison was made with control plants bearing only an equal number of standard B chromosomes. In the presence of deficient B, small B and small iso B chromosomes in the above plant series together with standard Bs, frequencies of pairing of the standard B chromosomes were markedly lower than the control plants containing only the corresponding number of standard Bs whereas the frequencies of standard B univalents were remarkably higher in the presence of the aforesaid derivatives of B chromosomes. This indicates that the dificient B, small B and small iso B chromosomes exert a suppressing effect on the pairing of the standard Bs; it may be due to the deficiency of a distal segment of the long arm of the standard B chromosome. The large iso B and medium B chromosomes have no such effect on pairing.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797228

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

Karyotypes of the blind catfishPimelodella kroneifrom three different caves in the southwestern part of the State of São Paulo, Brazil, and of its presumed ancestorPimelodella transitoriawere examined. Chromosome number and formula, as well as C-banding pattern and NOR location were found to be the same in both species, supporting the hypothesis of a close relationship and even conspecificity ofP. kroneiandP. transitoria.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797229

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

An intensely morphometrical study of the chromosomes ofLiza aurata, Liza ramadaandChelon labrosusis presented in this paper. We have found a very homogeneous karyotype for these three species formed by 2n= 48 chromosomes and 50 distinguishable arms, i.e. 46 acrocentric chromosomes and two biarmed ones. We have analyzed statistically the real lengths and the haploid relative lengths of the chromosome pairs of these species, the latter in order to neutralize the effect of the metaphase state on the variable variance. Using these data we have made a comparison between the chromosome complements of these three species, by mean of a fixed simple linear model of analysis of variance. This comparison supports the modern systematics of these species, and upholds the last evolutive criteria, observing bothLizaas being very near, andCh. labrosusshowing a certain distance. The specific study on the biarmed pair 24 has revealed these chromosomes as being submetacentric, with great differences between species for their lengths but with a strong homogeneity with respect to their arm ratio.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797230

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

The three species of cobitoids inhabiting the Iberian Peninsula were cytogenetically analysed—Cobitis calderoni, C. maroccanaandNemacheilus barbatulus.Metaphasic plates of specimens collected in several Portuguese and Spanish streams and, for the stoneloach, also in a central European river, were compared. All the species have a diploid value of 2n= 50 and are characterized by a high incidence of chromosomes with terminal/subterminal centromeres, particularly the cobitids. In spite of their phenotypical distinction, the spined-loaches karyotypes are grossly similar, suggesting only the occurrence of punctual chromosome rearrangements related to the respective differentiation processes. The lack of well-apparent interpopulation chromosome variability and the existence of diploid-polyploid relationships in these Euro-Asiatic families is finally discussed according to the new model of Cyprinidae karyological evolution.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797231

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

One of the most frequently reported cases of chromosome polymorphism amongst grasshoppers is the presence of supernumerary heterochromatin, involving either B chromosomes or supernumerary segments. Moreover, it has been long evident that these changes may exert intra- and/or interchromosome effects on chiasma frequency and/or position. In the present paper a cytogenetical analysis of 447 males ofLeptysma argentina(Acrididae: Orthoptera) revealed that two supernumerary segments (both of them sited in the smallest member of the karyotype) produce effects on chiasma conditions. The proximal segment (sp) precludes chiasma formation in the proximal region of the bivalent contiguous to the segment, causing a more distal chiasma repatterning; this effect is accumulative, since in sp homozygotes this pattern is significantly more evident. The interstitial segment (s1) causes a significant increase in chiasma frequency (due to enhanced proximal chiasma frequency) in some populations ofL. argentina, but not in others. Finally, it was noticed that the presence of heterozygous s1in the normally monochiasmate bivalent 10 raises average chiasma frequency of this bivalent from 1.00 to 1.24. This fact suggests that the presence of a discontinuity in pairing caused by the formation of a loop in the region of the segment—perphas due to a discontinuity in the synaptonemal complex—produces a relaxation of interference. However, other facts that reveal that interference, although relaxed, is still operative are mentioned and discussed. These facts suggest that the continuity of the synaptonemal complex may play a central role in the operation of interference.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797232

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

Chromosome numbers and karyotypes in some Orchid taxa are presented. In numerous populations ofOrchis coriophorasubsp.fragrans, chromosome counts yielded 2n= 36. At MI in EMC, there are usually 18 bivalents. However, we observed 16 bivalents + 2 trivalente in a few specimens. A specimen of O.coriophorafound near Mattinata was a triploid with 2n= 3x= 54. A karyological study ofBarila robertianarevealed a remarkable karyomorphology compared toHimantoglossum hircinum.A similar situation was found within theOrchisgenus when comparing O.tridentatawithO. lactea, and within theSerapiasgenus when comparingS. vomeraceasubsp.vomeraceawithS. vomeraceasubsp.laxiflora.Karyological correlations in some Orchid genera are discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797233

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor

摘要:

Specimens ofOryzomysaff.subflavuscollected in Central Brazil displayed a karyotype with 2n= 58 and FN = 70, not described previously. Sex chromosomes polymorphisms were identified: the X could be a large submetacentric (Xa), a large subtelocentric (Xb) or a large subtelocentric smaller than Xb (Xc) and the Y appeared as a medium submetacentric (Ya), a medium subtelocentric (Yb) or a medium acrocentric (Yc). G- and C-banding, as well as chromosomal measurements were used to establish the rearrangements involved in the sex chromosomes variability.

ISSN:0008-7114    

DOI:10.1080/00087114.1992.10797234

出版商:Taylor & Francis    

年代:1992

数据来源: Taylor