摘要:

De nombreux croisements expérimentaux entre des taxons morphologiquement affines, ont permis d'obtenir plusieurs hybrides interspécifiques (F1et F2) à partir de parents appartenant à des espèces allopatriques ou marginalement sympatriques. Le comportement méiotique des cellules mères de la F1a été examiné afin de déceler l'existence et le pourcentage d'anomalies traduisant le degré des barrières internes d'isolement et d'homologie des chromosomes.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796761

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

The embryology of two apomictic parents, R473 and 302 has been investigated. The anther structure conforms to the Monocot type. Cytokinesis takes place by the successive method. Ripe pollen is 3-celled. Though 90% of the pollen is fertile the germination is only about 60%. The embryosac developes aposporously from a centrally located nucellar cell. Fertilization does not take place. The development of embryo and endosperm takes place autonomously under the stimulus of pollination. The present study confirms earlier report of somatic apospory and autonomal development of endosperm and embryo in R473 by RAO and NARAYANA (1968). In addition an additional case of somatic apospory in 302 variety is now reported.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796762

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

The variation in chromosome number found within one and the same endosperm in species ofCoffeacan probably be ascribed to: 1) endoreduplication producing cells with euploid chromosome numbers, multiple of the initial ploidy level; 2) endoreduplication of only some of the chromosomes; 3) unequal anaphases. The mechanisms 2 and 3 would produce cells with aneuploid chromosomes numbers, at any ploidy level. Such phenomena occur either independently or concomitantly.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796763

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

This paper shows that extracts fromZephyranthes robustaBaker and a constituent alkaloids haemanthamine and lycorine inhibited mitosis inAllium ceparoot tips.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796764

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

A new chromosome count (n= 36) inN. furcatasubsp.flagelliferaf.patulahas been established. The cytological characters of this taxon have been compared with other taxa ofN. furcatacomplex justifying its merger. It has also been emphasized that polyploidy is not always associated with altitude in Charophytes.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796765

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

The males of the NICD strain ofAnopheles stephensiwere exposed to 4000 R of Co-60 Gamma radiations at the rate of 188 R per minute and then mated with virgin females of the same age group. The salivary chromosome preparations from 4th instar larvae of F1progeny revealed 40 heterozygous aberrations involving deletions, inversions, translocations and complex rearrangements, however with variable frequencies. The frequencies of breaks per sperm and the mortality induced, thereof, have been determined. It has been concluded that gamma-rays act specifically but not at random. From the available data, it has been deduced that chromosomes had a spiral structure and polar field type of orientation during the irradiation of spermatozoa.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796766

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

Somatic chromosomes of the guppy,Poecilia reticulata, were analysed from some tissues of twelve individuals by air-drying method and the diploid number was determined to be 46. The karyotype is composed of 23 chromosome pairs exclusively of acrocentric type. The sex chromosomes of this digametic species were morphologically unidentifiable.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796767

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

Viene ulteriormente avvalorata l'ipotesi che le specie appartenenti alle famiglie Cionidae e Diazonidae vadano raccolte in una unica famiglia. La famiglia Perophoridae rimane, anche a livello cariologico, ben separata dalle altre famiglie e sembra sia da riconsiderare l'ipotesi di una sua primitività nell'ambito del sottordine Phlebobranchiata. Una stretta affinità cariologica viene individuata tra i generiPerophoraedEcteinascidia.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796768

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

Four nulli-tetrasomic lines ofTriticum aestivumvar. Chinese Spring were backcrossed to T.durumvar. Cappelli.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796769

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor

摘要:

Esaminando i cromosomi di dieci specie appartenenti alla famiglia Styelidae, sono stati raccolti alcuni indizi che indicano come primitivo il carattere « precoce attività centromerica ». Smettendo alcuni dati precedenti è stata provata l'alta uniformità cariologica del genereSlyela.

ISSN:0008-7114    

DOI:10.1080/00087114.1978.10796770

出版商:Taylor & Francis    

年代:1978

数据来源: Taylor