摘要:

Endospermi di mandorlo (Prunus amygdalusStokes) ancora apociziali o all'inizio della cellularizzazione sono stati esaminati al microscopio elettronico. Si descrivono le principali strutture osservate e si indicano alcune particolarità della membrana esterna, della zona a cellularizzazione irregolare e di « strutture a coppa » assai abbondanti prima della cellularizzazione definitiva.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796047

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

1.The results of the cytological studies in the endosperm ofZephyranthes ajaxSprenger have been reported.2.Alpha bromonaphthalene and 8-hydroxyquinoline were found to be very effective in spreading the endosperm chromosomes.3.The endosperm was free nuclear upto 4 days after pollination. The 5 to 6 day old endosperm was cellular.4.The endosperm, especially at the free nuclear stage, showed a striking variation in the size and shape of nuclei. The range in length and breadth of nuclei in the 4 day old endosperm, for example, was 16μ to 280μ and 8μ to 160μ respectively. The variation was equally striking in the central and the peripheral region.5.Polyploidy, aneuploidy, amitosis and nuclear fusion were found to be the main causes for the variation observed in the size and shape of endosperm nuclei. Split anaphases, tripolar spindles and lagging chromosomes were responsible for the formation of nuclei with aneuploid numbers. The normal cytological constitution of the endosperm was regarded tetraploid (4n= 84) as 85 per cent of the nuclei showed this condition.6.Analysis of the nucleolar numbers and chromosome counts of the endosperm and root tip nuclei have shown that the number of nucleoli per nucleus cannot be used as an index of polyploidy inZephyranthes ajax.7.A study of the nuclei at 2, 4, 6, 8, 10, 12 and 14 days after pollination did not reveal any definite constant relationship between size of nuclei and age of endosperm.8.The endosperm failure was possibly caused by the cumulative effect of mitotic abnormalities which were exhibited in the form of bridges, laggards and rings. High degree of polyploidy, aneuploidy and amitosis also characterised the degenerating cells of the endosperm.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796048

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

Perennial teosinte was found to be a modified autotetraploid with a reduced chiasma frequency and an extension of chiasma interference across the centromere. This apparently simple modification has reduced quadrivalent frequency and has restricted quadrivalent types to rings and chains. Meiosis is nearly always regular and 93% of perennial teosinte seedlings were euploid. It is considered that since chromosome stability may be so easily attained, autotetraploids may be an important source of evolutionary variation.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796049

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

In un ceppo di cellule di rene di cavia coltivate in vitro sono stati studiati gli effetti citologici dell'irradiazione con dosi diverse di raggi X, con particolare riferimento alle modificazioni dell'attività moltiplicativa e alla comparsa di varie alterazioni nucleari.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796050

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

The Orchidaceae is unusual in that placental proliferation and ovule formation generally occur after anthesis and require pollination to stimulate development. In this study the normal sequence of ovule development in relation to time after pollination in two species ofPhalaenopsis(P. pulcherrima, P.X Chieftain) belonging to different sections of the genus is discussed. P. X Chieftain is approximately ten days slower in attaining any given stage when compared toP. pulcherrima.The slowness in development ofP.X Chieftain is probably due to its tetraploid nature rather than to the sectional difference of the two species involved.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796051

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

In a research programme on the karyological aspects of evolution in Primates the author in the present paper shows the results of a morphometric comparative analysis between the chromosomes of Man and the Anthropoid Apes.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796052

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

È stato descritto il cariotipo diChrysanthemum cinerariaefoliumVis.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796053

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

The chromosome number forHydrodictyon reticulatumLagh. has bem determined to be 18, lending support to PROSKAUER (1952), contrary to the observations of PALIK (1949). Several karyological effects following colchicine treatment, including induction of polyploid and deficient nuclei in some segments are described and compared with those ofSphaeroplea.Abnormalities in the morphology of daughter coenobia liberated from the material transferred to colchicine-free medium subsequent to colchicine treatment have been described and possible causes for the abnormalities have been discussed. Production of abnormal daughter coenobia even in the second generation without colchicine treatment points to the view that the abnormalities produced are probably genetic.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796054

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

In the present paper the autor reports a chromosome number of 2 n = 48 and on the morphology of chromosomes in an allopolyploid species ofAllium strictumSchrad.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796055

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor

摘要:

The chromosome number ofCitrus Assamensishas been found to be 2n — 18. Though it is ordinary diploid species yet it shows multivalent formation ranging from trivalent, quadrivalent to esavalent. The bridge fragment configuration has also been observed at anaphase. The second division is marked by stray chromosomes and laggards. The pollen sterility is 45%.

ISSN:0008-7114    

DOI:10.1080/00087114.1962.10796056

出版商:Taylor & Francis    

年代:1962

数据来源: Taylor