摘要:

Allium rubellumBieb. so far known as a diploid and a triploid has been collected in the tetraploid form (2n=4x=32) from the saffron fields and mud built house tops of Kashmir valley. Tetraploidy has caused gigantism in the size of the plant and the flower head. Root tip cells bear 32 chromosomes with median or submedian centromeres. Eight of the chromosomes are secondarily constricted. These do not match into pairs. Meiosis is characterized by a high frequency of quadrivalents ranging in number from 8 (maximum number possible) to 2 per cell. Anaphase distribution is regular in almost half of the microspore mother cells and only slightly irregular (17:15) in the rest. The subsequent course of meiosis is perfectly normal and as a consequence healthy pollen grains are produced. Though the high quadrivalent frequency points to autopolyploidy, in view of the karyotypic heteromorphicity the taxon seems to have arisen through hybridization at the varietal level.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796422

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The chromosomes of three species ofCallosobruchus(Bruchidae: Coleoptera) have been studied in the male germ cells and nervous tissue of both the sexes. The karyotype is in confirmation with the basic type advocated for Coleoptera i.e. 9AA-XyDmale and 9AA-XX female. X and Y chromosomes form a typical parachute during first meiotic division. The Y-chromosome is, however, the smallest. Intraspecific variations in the chromosome number, by the loss of Y-chromosome, have been noted inCallosobruchus maculatusF. andC. chinensisL.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796423

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

From the study of somatic chromosomes ofDracaena metallicaHort., which shows a high degree of variation in chromosome number, and which is propagated exclusively by vegetative means, it is clear that the chromosome numbers have got some common characteristics in all the offshoots. Counting of a large number of plates in the root tips of different offshoots shows the repetition of almost similar types of chromosome numbers which tend to remain as multiples of 7. In spite of this homogeneity in the offshoots, differences in the tendencies of variation were noticed, particularly in the occurrence of the most frequent chromosome numbers. In the long run, such differences may lead to the production of new species having distinct chromosome complements.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796424

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

A study of the meiotic behaviour and transmission of accessory chromosomes in a British population ofC. pyrenaicaDC. (C. alpinaWats.) has been carried out. The accessories are euchromatic but smaller than the A-chromosomes. They occur in 78% of the individuals sampled and are constant in number in all the cells of an individual. All the accessories are morphologically identical and in no cell has any association between the accessories and the A-chromosomes been observed. The accessory chromosomes behave normally at mitosis. During meiosis their behaviour differs from that of the A-chromosomes in that at metaphase I they are sometimes associated together to form accessory ‘bivalents’ or ‘multivalents’. At anaphase I the paired accessories segregate in the same way as the A-chromosomes. Unpaired accessories, however, do not divide and are generally incorporated in one of the daughter nuclei. At anaphase II the accessories divide and segregate regularly. There is a significant difference in the transmission of accessories through the male and female lines. The accessories are preferentially eliminated from the male line and retained in the female line. This provides a possible mechanism for their retention at a constant level and frequency in the population.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796425

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Etudes cytotaxinomiques de plusieurs taxons du genreLinariadu bassin méditerranéen occidental.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796426

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Chromosome counts for two genera and five species have been investigated for the first time. The genera arePogostemonwith two species (n=30) andElsholtziawith four species (n=8). The new counts for species are:Micromeria biflora(n=15),Calamintha clinopodiuK(n=10),C. umbrosa(n=10),Melissa parviflora(m=8) andMosla ocymoides(n=9). Evolution of base numbers in the tribe Satureineae is discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796427

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

An analysis of mitotic index, labelling index and nuclear DNA content in differentiating cells of roots inVicia fabaandLactuca sativahas shown a different behaviour of cell differentiation in the two species.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796428

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Nineteen different chromosome numbers ranging from 2n=18 to 96 have been obtained from an analysis of 8 species and 65 garden cultivars of the genusZephyranthes.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796429

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The chromosome complement (2n) in the males ofDistantiella theobromaandSahlbergella singularisin 26A+X + Y each and the complement inBryocoropsis laticollisandHelopeltis corbisiertis 32A+X+Y and 16A+X + Y respectively.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796430

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Taphozous melanopogonandT. l. longimanus(family Emballonuridae, have 2N=42,Megaderma I. lyra(family Megadermatidae) has 2N = 54 andHipposideros fulvusandH. a. ater(family Hipposideridae) have 2N=32. The chromosomes of Megadermatidae and Hipposideridae have been studied for the first time. Interrelationships on the basis of available chromosome data and also the probable mechanisms of karyotype evolution in these Indian species of Microchiroptera are discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796431

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor