摘要:

The chromocentres in nuclei of germinating radicles ofBryonia dioicanormally disperse before the onset of DNA synthesis. Inhibitors of DNA synthesis enhance the frequency of such disperse nuclei. Later, when the meristem of the rootlets is established, there is a good correspondence between the disperse Z phase morphology and DNA synthetic activity in such nuclei. When roots are exposed to inhibitors of DNA synthesis Z phase persists but the correspondence with DNA synthesis is broken. It is proposed that chromatin dispersion is not dependent upon DNA synthesis, and that chromatin condensation/decondensation and DNA synthesis are markers of two separate cyclical processes that occur in proliferating cells.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797696

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

In root meristem cells of two cultivars ofHelianthus annumL., which slightly differ in 2C DNA content, a comparison was made on the following parameters: heterochromatin content, duration of the cell cycle and of some of its particular phases, growth and sizes of cells in the course of interphase, frequency of proliferating cells, RNA, protein and dry mass content in nucleus, nucleolus and cytoplasm, as well as the content of condensed chromatin in consecutive phases of the cell cycle. It was found that in cv. Pionier—which is characterized by lower content of DNA and heterochromatin, smaller cells and a greater increase in dry mass and protein during the G2phase—the cell cycle lasts 14 h, whereas in cv. Jadalny it lasts 10 h. In both cultivars, the content of condensed chromatin and RNA is similar. The frequency of ring nucleoli increases at the G1/S, S/G2, and G2/M transitions of the cell cycle. It is assumed that an increase in dry mass content may play the role of regulatory factor of the cell cycle duration. The productivity of meristem, i.e. the increase in dry mass and protein content after successive cell cycles, was found to be some 22% higher in cv. Jadalny.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797697

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

Nothoscordum fragranschromosomes were mildly prepared by enzyme maceration and subsequent air-drying. Cytological characteristics of heterochromatic segments were studied by the C-banding technique, fluorochrome-staining and treatment with chemicals. Results showed that at least two classes of heterochromatic segments were differentiated with regard to the base composition of DNA and treatment with various chemicals or enzyme solubilized the heterochromatic segments comprised of GC-rich DNA.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797698

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

Analysis of mitotic and meiotic chromosome spreads from testicular, ovarian and uterine tissue ofParadistomoides orientalisrevealed a diploid number of 28 for this species. The karyotype consisted predominately of biarmed chromosomes forming a gradual relative length series. Serial squashes of the oviduct and the proximal region of the uteri were used to follow chromosome behaviour at various stages of zygote formation. Based on these studies, early divisions of the oogonia were found to occur in the ovary whereas metaphase-1 spreads from the primary oocyte were observed in the ootype region. This region was also marked by the entry of the sperm into the ooplasm of primary oocyte. Once inside the egg, sperm chromatin formed fourteen thread like chromosomes termed as precondensed chromosomes. Primary oocyte pinched off 1st polar body nucleus followed by 2nd meiotic division. After releasing 2nd polar body nucleus, prophase chromosomes of the female pronucleus and precondensed chromsomes from the sperm nucleus passed directly in to metaphase of the first cleavage division. No fusion between male and female pronuclei was observed.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797699

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

Nuclear DNA content was determined in 17Rutaceaespecies. The results obtained suggest that both nuclear DNA content and mean chromosomal DNA content appear to be very sensitive indicators of the kin relationship between species or genera. The variation in nuclear DNA content amongRutaceaeis mainly determined by high ploidy levels. Diploid and tetraploid species generally have a 4C of less than 5.5 pg, whereas those with higher ploidy have a 4C of more than 12 pg. The few exceptions in this tendency are encountered in species from temperate regions where the evolutionary strategies at the chromosome level seem to diverge from those developed by tropical plants.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797700

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

At 10−3M, isovitexin, a C-glycosylflavone isolated from leaves ofRhynchosia minima(Leguminosae), inhibits cell plate formation resulting in the production of binucleate and occasionally multinucleate cells. A 48-hour treatment caused nucleolar fission leading to multinucleolate condition. At 10−5M and 10−7M, isovitexin seldom induced any cytologic abberations, but promoted mitosis up to 48 hours from treatment and suppressed it thereafter. The potentialities of isovitexin render it useful in studies on cell cycle and as a cytokinin-like substance.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797701

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

The karyotype and microsporogenesis of triploidCrocus sativuswere studied. The high percentage of trivalents observed at metaphase I (on average, 7.3 trivalents per cell) together with the karyotype configuration confirm autotriploidy. Some considerations about the presence of one unique chromosome in the karyotype and about the origin of triploidy are presented.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797702

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

Meiotic analyses of the hybrids obtained in crosses with the 12 double-ditelocentric and 2 ditelocentric lines from A and B genomes ofTriticum aestivumL. cv. «Chinese Spring» were carried out to identify the chromosomes involved in an induced interchange in the cv. «Senatore Capelli» ofTriticum turgidum durum(2n= 4x= 28). A karyotype analysis of plants carrying the interchange was also carried out and compared to that showing the standard constitution. From these studies it was concluded that the chromosomes involved in the interchange in cv. «Senatore Capelli» were 7A and 5B.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797703

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

In this work the results of karyological investigations onPithophora pragenstsŜula are reported. The chromosome number for this species has been established as 2n= 24. It is the first count of chromosomes forPithophora pragensts.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797704

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor

摘要:

G- and C-band pattern and NOR's ofTalpa occidentalismetaphase chromosomes are described. The C-band pattern shows that the chromosomal pair causing karyotypic differences in the genusTalpapresents their short arm totally heterochromatic. The implication of this fact in the karyotypic evolution of this genus and the taxonomic status ofT. occidentalisare discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1984.10797705

出版商:Taylor & Francis    

年代:1984

数据来源: Taylor