摘要:

The present communication deals with a discussion on the significance of chromosome numbers in Charophyta. After presenting a brief review of the various views held on the basic chromosome numbers in the taxa ofChara, NitellaandTolypella, the role of polyploidy in the evolution of Charophyta and the possible ways in which polyploid taxa might have originated in nature have been considered. On the basis of present evidences aneuploids seem to show restricted geographical distribution as compared to euploids. Maximum degree of polyploidy has been found to be prevalent inChara zeylanicawithin the tribe Chareae andNitella tenuissimaandNitella furcatawithin the tribe Nitelleae. Significance of polyploidy in relation to sex, taxonomy, external form, chromosome length, pH, and altitude has also been discussed with some specific examples.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796447

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The author makes a critical examination of present embryological data regarding the Podostemaceae family.1°The oldOenonetype (CHIARUGI 1927) is changed to theApinagiatype.2°Four different forms of theApinagiatype are distinguished:a)Apinagiatype form A (5-nucleate, 4-celled),b)Apinagiatype form B (4-nucleate, 4-celled),c)Apinagiatype form C (5-nucleate, 5-celled),d)Apinagiatype form D (6-nucleate, 4-5-6-celled).3°TheDicraeatype is completely valid.4°ThePodostemumtype (formerlyPodostemon) is considered as not definitely ascertained. An investigation would seem absolutely necessary particularly forPodostemum subulatus(MAGNUS 1913), the first example of this embryological type.5°Some embryological findings regardingTerniola(=Lawia)zeylanicaandGriffithella hookerianaare discussed critically.6°The morphology of the mature embryo sac of the Podostemaceae is interpreted differently to the accepted way. In such embryo sacs, according to the author, the proendospermatic cells, the polar nuclei and the so called double fertilisation are totally lacking, justifying the general and constant lack of endosperm. The author, in other terms, attributes the value of « antipodal cell nucleus » to that nucleus which other authors have always considered as « the polar nucleus ».7°As a result of the data in the above point 6°, the author considers that it is more exact to say that in the Podostemaceae areduced bisporicgametophyte is present rather than areduced Allium typegametophyte.8°The different embryological types of Podostemaceae are described according to the theoretic interpretation the author has previously formulated (Battaglia1951, 1955, 1963).

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796448

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Cytological investigations on eightCamelliaspecies and three related genera belonging to the family Theaceae have been made.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796449

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The cytological behaviour of the seven primary simple trisomies in pearl millet was studied. Positive correlation between the trivalent frequency and the lenght of the extra chromosome in all the trisomies was observed which is of help in the identification of different trisomies at diakinesis. The distribution of chromosomes at anaphase I and II was mostly normal.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796450

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The cytogenetics ofChthonerpeton indistinctumwas studied. The karyotype was composed of five pairs of metacentric chromosomes, four pairs of submetacentrics and one pair of telocentrics (diploid number 2n= 20).

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796451

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The behaviour of chromosomes during meiosis in four species of grasshoppers has been studied. The diploid chromosome number in male in all the species is twenty three. All the chromosomes are acrocentric. Chiasma frequency and terminalisation coefficient studies have been made in detail. Some chromosomal abnormalities like anaphase bridges, supernumerary chromosomes are also seen. Metrical study from second division meiotic chromosomes have been made.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796452

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Cytophotometric analysis of nuclear DNA and histone content were made in dividing and nondividing root meristems ofTriticum durumcv. CAPPELLI. It was demonstrated that the nuclei in the pre-DNA synthesis phase of the nuclear cycle (G1), all having a 2C DNA content, show very different amounts of fast-green stainable histone. The 2C nuclei in nonproliferating meristems of caryopses at 15 days before harvest have a histone content nearly twice that of 2C nuclei in proliferating meristems of germinating caryopses.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796453

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The DNA/histone ratio was calculated through Feulgen/fast green absorption in different regions of polytene chromosomes inPhaseolus coccineusembryo suspensor cells. A great variability of ratios, related with the structural characteristics of DNA in the different regions, has been found. This seems to indicate that complexes of histone with DNA may depend on changes in DNA metabolic activity. In one and the same cell, and even in one and the same chromosome, different chromosome segments have different DNA/histone ratios.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796454

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Histophotometric evaluation of the DNA content of the post-kinetic nuclei (lymphocytes) has been performed in 8 species of Palearctic Microchiroptera:Rhinolophus ferrumequinum, R. euryale, R. hipposideros, Miniopterus schreibersi, Pipistrellus savii, P. kuhli, Myotys myotisandM. capaccinii.The results obtained are compared with the known data (CAPANNA and CIVITELLI 1970) on the morphology of the karyotype of these species and are discussed whith a view to explaining the relationships between chromosome transformations and variations in DNA content.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796455

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Karyometric analysis was made of two palaearctic species of bats:Plecotus auritusandPlecotus austriacus.In both species the number of chromosomes was shown to be identical (2N=32) and also the number of arms of the chromosomes (NF = 54, NFa = 50). The relative length of chromosomes in both species are not significantly different. Significant differences, however, were found in the position of centromeres for three pairs of autosomes and X-chromosomes.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796456

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor