摘要:

In the planarian species,Dugesia lugubris, two biotypes are found: E (2n = 8, n = 4) and F (2n = 6, n = 3); on the basis of karyometric studies it has been hypothesized that the second was derived from the first through a Robert-sonian mechanism of centric fusion. The quantitative cytochemical data reported here confirm the hypothesis of karyotype evolution, since there are no significant differences between the DNA content of the nucleus in the two biotypes. The regenerative blastemas of both biotypes contain a number of cellular populations with a variable Feulgen-DNA content; these correspond to successive doublings of the 2C diploid content. In addition, metaphase plates with multistranded chromosomes have been found. A difference between the chromosome C-banding in the two biotypes has also been observed.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796880

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796881

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

Columnar epithelium and parenchyma cells of the scutellum ofTriticum durumcaryopses show different quiescence models: while epithelium cells display a DNA content per nucleus of 2C, the parenchyma cells undergo poli- ploidization. Furthermore, in old seeds, the distribution of the histones/DNA ratio shifts much more in parenchyma cells than in columnar epithelium cells. It may thus be concluded that different tissues of the same organ (scutellum) are affected in a different way by damaging effect of ageing factors.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796882

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The female gametophyte development in the fourteen investigated taxa of the Eriocaulaceae conforms to thePolygonumtype. Three circumaxial antipodal cells are organized at the chalazal pole of the embryosac. The size and form of cells vary in different taxa. The cells lose their walls prior to the fusion of polar nuclei within the embryo sac. A conspicuous antipodal cyst develops by the coalescence of the three naked protoplasts. This is followed by the enlargement and subsequent fusion of nuclei. The triploid nucleus undergoes hypertrophy. The cyst breaks down soon after the secondary nucleus is organized and when the central cell begins to elongate. A nutritive role is ascribed to the antipodal cyst. This unique behaviour of the antipodals is a consistent character of the Eriocaulaceae of the Old and the New Worlds studied.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796883

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The karyotype and male meiosis of three species of Psychodinae were examined. The trend of meiosis is very similar in the different species apart from a little variation observed inBerdeniella sp.Karyotypic analysis of these species as well as of these already studied belonging to the tribe Pericomini apparently shows differences only on the sex-chromosomes size. On this basis some hypotheses were suggested and discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796884

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The cytotaxonomic comparison betweenIris palestinaBoiss. andIris alataPoir., shows that they are closely related. The main differences between the two species include a) the area of distribution and b) the size of at least one of the chromosome pairs as well as differences in the number and location of secondary constrictions. Relatively small karyotype differences also exist betweenI. palestinafrom Israel and from Lebanon and also betweenI. alatafrom different localities in Sicily.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796885

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

Triploid (2n= 3x+ 36) cytotype ofTulipa clusianavar.stellatahas been recovered from Kishtwar plateau located south-east of Srinagar. Except for number, the fundamental karyotype of triploid plants is essentially similar in detail to other cytotypes ofTulipa clusiana.The monoploid set consists of one submetacentric and eleven subtelocentric chromosomes. Attemps made to explain the nature of triploidy on grounds of karyotype and meiotic behaviour favour origin of triploid plants through autoploidy.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796886

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

Chromosomes of the following four species ofPolisteswasps from the Bryan-College Station area in Texas are reported:apachus, n = 22 or 25; exclamans, n = 33;metricus, n = 26; and carolina, n = 19, 2n = 38. The karyotype of P. carolinawas constructed and revealed that chromosomes no. 16 and no. 19 are acrocentric whereas the others are metacentric.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796887

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The nucleolar organizer activity was studied in the salivary gland cells ofDrosophilaspecies from the ‘mulleri’ complex and their hybrids. The association of nucleoli with chromosomes showed that intraspecifically the X chromosome and the microchromosome are involved in the nucleolar synthesis in every case: the first as the main nucleolus organizer and the second apparently as a minor site operating in a low number of cells. Hybrids, however, revealed interspecific differentiation in the nucleolar activity and its control. In the female progeny from every interspecific combination nucleolar dominance was a constant feature, but the specific origin of the dominant nucleolar organizer varied among different combinations. In the male hybrids interspecific variation was detected by the occurrence, in some combinations, of an activation of the microchromosome to operate like the main NO, associated with gene amplification. The degree of gene amplification was another feature which varied among those combinations. These findings were discussed in view of the phylogenetic relationships of the species, previously established on the basis of cytological and genetical analysis.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796888

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor