摘要:

The pellicle of five species ofEuglena, belonging to three different groups (Catilliferae, Radiatae and Serpentes), was studied by transmission electron microscopy, in order to see if pellicular morphology could be taken as a valuable character to differentiate the groups. The data demonstrate that pellicular ultrastructure is not constant within the groups, and can therefore be considered a differential character only at the level of species.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796906

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The chromosome complement ofB. purpurocaeruleashows a pattern of Quinacrine bands of the reduced type, that coincides both with the pattern of Giemsa C-bands and with the Feulgen band pattern shown by GRAU (1966). Quinacrine staining provides the best definition of karyotype details. The correspondence of Q-bands of the reduced type to positively heteropycnotic Feulgen bands is also briefly discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796907

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

A treatment with the analogue of thymine 5 Aminouracil (5-AU) can induce, some time after its removal, a good mitotic synchronization in root meristems of higher plants. The mechanism of action of 5-AU is still unknown. According to some Authors 5-AU may act by inducing an accumulation of the cells in some specific point of the cell cycle (the S phase in general, the end of the S phase, or G2). Since we showed in a previous work that nuclei in the last part of the S phase replicating heterochromatic DNA can be cytologically identified on the basis of their peculiar labelling, we used this feature as a tool to elucidate the stage of the S phase in which the cells grown in 5-AU appear to be blocked. According to our results, this point should be in the last 1/3 of the S phase, just before the onset of heterochromatic DNA replication.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796908

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

Somatic chromosomes of 15 roses: diploid, triploid, tetraploid and pentaploid were studied. The chromosomes were grouped into types based on their relative lengths and arm ratios. The longest chromosome of a complement was found to be twice the length of small chromosomes. Two small chromosomes possessed nucleolar organizing regions both in diploids and tetraploids. Additional evidence was obtained from the PMCs where one bivalent was found attached to the nucleolus. There were a few minor differences in the karyotypes of theRosaspecies, hybrids and cultivars, which could be attributed to the hybridization and prolonged hystory of cultivation of roses.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796909

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The analysis of the meiotic behaviour of the PMCs ofDipcadi serotinum(Liliaceae) (2n= 8 + 0–4 B) revealed an unusually high frequency of several types of abnormalities: chromosome breakage, pairing failure of chromosomes, irregular anaphase segregations etc. The possible origin of these meiotic abnormalities is discussed in relation to other characteristics of the genetic system of this species, as the existence of gene duplication phenomena.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796910

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The presence of only a single satellited chromosome in the chromosome complement ofAllium cepawas recorded. By means of Giemsa staining, silver staining and C-banding, cytological studies of the chromosomes were carried out in bulbs with a single, two, three and four satellited chromosomes. The presence of the satellites was limited to the subtelocentric (st) and the shortest metacentric (m3) chromosomes. Although the satellites were higly polymorphic in size and staining intensity, all proved to be active for nucleolus formation as revealed by silver staining. The st chromosomes were easily discriminated into two types and the m3 into three types by C-banding. It is concluded from the present observations that both the translocation and deletion may be concerned in numerical variation of the satellited chromosomes and the polymorphism of the st and m3 chromosomes.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796911

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

Chromosomes of two species of earwigs viz.,Diplatys gladiatorBurr and D.rufescens(Kirby) are described. These two species are characterized by the possession of 18 chromosomes in the diploid set of both the sexes, with XY and XX sex mechanism in the male and female respectively.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796912

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The distribution of insoluble polysaccharides, DNA, RNA, total proteins and histones have been studied in the developing ovule ofLinaria bipartita.The distribution of the above metabolites has been observed in the nucellus, integument and integumentary tapetum with a view to understand the role played by these tissues. The cytochemical details of the nucellus show that the nucellar cells in tenuinucellate ovules do not have a significant role in providing nutrition to the embryo sac. In the absence of a vascular supply to the funiculus, a group of elongated and thin-walled cells seems to be transporting food materials from the placenta to the chalaza. Cytochemical details of the integumentary tapetum assign a high metabolic activity to this tissue. It is possible that a part of the nutrients from the chalaza of the ovule is transported to the micropylar end of the embryo sac, through the integumentary tapetum. Therefore, the present study indicates that the nutrients are supplied to the embryo sac both at the micropylar and chalazal ends. The possible pathways of nutrition to the embryo sac before and after fertilization is depicted diagramatically.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796913

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

The cytogenetic study ofDeltamys kemptshows a diploid complement of 37 chromosomes in both sexes. The somatic complement consists of 36 acrocentric chromosomes and one odd submetacentric chromosome which has presumably arised in an X-autosome translocation. Thus, the female would be heterozygous for the translocation with an odd chromosome number the same as the male. Consequently, it can be assumed that this is a preliminar stage in the evolution of a multiple sexual mechanism of the XY1Y2/XX type. In the male meiosis an XY1Y2sexual trivalent can be observed. In the 32 per cent of the plates the dissociation of the trivalent into two components could be detected. One of them is a classical mammalian XY complex; the other is an asimetric autosomic complex which is structurally analysed. This fact confirms the occurrence of an X-autosome translocation.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796914

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor

摘要:

Cytological analysis ofPeliosanthes macrophyllaWall, ex Baker andP. violaceaWoll. ex Baker indicates that both of them bear 2n= 36 chromosomes. The meioses studied are normal. The transfer ofPeliosanthesfrom Haemodoraceae to Liliaceae by Hutchinson is justified as the chromosome morphology of this genus is related to that of the different tribes of Liliaceae. Chromosome complements show a clear cut gradation in size from large, medium to small. Karyotype analyses crearly indicate that structural alterations of chromosomes have played a significant role in the evolution of the genusPeliosanthes.The chromosome numbers of these two Indian species of Peliosanthes are reported for the first time.

ISSN:0008-7114    

DOI:10.1080/00087114.1981.10796915

出版商:Taylor & Francis    

年代:1981

数据来源: Taylor