摘要:

1.Nothoscordum fragranshas colonised a wide range of habitats and, once introduced, can spread to become a weed.2.In a clone of this species with a heterozygous complement (2 n=19=13L + S) similar to those described by previous investigators, the ovules contained more than one embryo. After fertilisation, an embryo with a suspensor could be identified in some embryo-sacs. Usually, after competition for food reserves, only one seedling from each seed reached maturity, and this was frequently from an adventive nucellar embryo.3.Non-disjunction and lagging of unpaired univalents at meiosis, particularly S chromosomes of the heterotrivalent, result in many aneuploid pollen grains, but about 50% of pollen tubes were capable of reaching the ovule. A weak infertile aneuploid (2n +1 = 20 = 14L + 6S) was raised by artificially separating seedlings produced by one seed.4.None of the expected aneuploid or structurally homozygous products of sexual reproduction survive under natural conditions.5.It was concluded that vegetative and apomictic reproduction affects the rapid spread of genotypes produced by sexual reproduction. A system involving balanced lethals and polyembryony eliminates all but the best adapted, heterozygous individuals in this species with enforced inbreeding. Structural heterozygosity is not an essential feature of this mechanism, but as it involves nucleolar chromosomes, is perhaps preserved for its effect on chromosome activity.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796267

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

Cytology ofIochroma tubulosaBenth has been studied. It showed 12 bivalents in PMC and 24 chromosomes in root tip cells. The various abnormalities observed in PMCs and karyotype analysis suggest that this taxon is of possible hybrid origin. This is also borne out by the total absence of fruit setting and the high percentage of pollen sterility observed in these plants.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796268

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

The study of the influence of the 3′-adenylic acid on cell division has shown that it has an inhibiting effect. This substance also produces various types of chromosomal aberrations, especially the picnosis phenomenon. By studying the effect of adenine, adenosine and 3′-adenylic acid on the mitotic cycle inVicia faba, adenine and the 3′-adenylic acid have been found to considerably increase the length of the mitotic cycle. The authors consider that the strong effect of the 3′-adenylic acid upon the nucleus and the chromosomes is probably due to the DNA depolimerization (fact pointed out by the picnosis phenomenon). This also contributes to the blocking of the macromolecules synthesis by the deoxyribonucleic acid.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796269

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

The chromosome number ofT. ligusticumwas found to be 2n = 12, and that ofT. cherleri2n = 10. A comparison of the chromosomes of these species with those ofT. hirtum(2n=10) andT. scabrum(2n = 10) showed that the karyotype of each species has distinctive features, but some chromosomes of the species with 2n = 10 are similar in size and shape and may be homologous.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796270

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

The relation between cotyledon water content and following processes: i) DNA synthesis in cells of the radicle meristems, ii) mitotic activity in the meristems, iii) accumulation of storage material, has been studied during ripening of seeds inVicia faba.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796271

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

In a study of the meiotic chromosomes ofMacaca, the mean chiasma frequency has been found to be between 1.9 and 2.1. No instances of translocation or insertions were seen. It is suggested that the Y chromosome pairs with the terminal portion of the short arms of the X chromosome. The marked chromosome pair has been identified and its behavior, followed through meiosis, suggests that the achromatic zone has an inhibitory action on the formation of chiasmata.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796272

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

The diploid number ofLacerta sicula campestrisis 2n = 38. All the chromosomes are telocentric and morphologically recognizable heterochromosomes are absent.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796273

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

摘要:

In cells culturedin vitroBeryllium exerts a damaging action on all the mitotic phases. In high concentrations (1×10–3M) such action is stronger on lymphocytes than on kidney cells.

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796274

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor

ISSN:0008-7114    

DOI:10.1080/00087114.1967.10796275

出版商:Taylor & Francis    

年代:1967

数据来源: Taylor