摘要:

Chromosome numbers and meiosis in 164 interspecific hybrids representing 17 combinations ofS. officinarum(2n=80) xS. spontaneum(2n= 54, 56, 61, 63, 64 80, 112, 124 and 128) are reported. Hybrids involvingS. spontaneum2n= 61, 63 and 124 as the pollen parents are reported for the first time.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796591

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Cytology and development ofEntyloma thirumalachariPavgi and Singh, parasitic onBlumea oxydontaDC. have been described. During teliospore germination, the diploid nucleus migrates into and divides in the promyceliuin. The first division is reductional followed by an equational one. Some of the meiotic divisional stages were observed and the haploid chromosome complement determined to ben= 6. Several aberrations in teliospore germination and nuclear behavior were observed and their repercussions discussed. Sporidial development and their conjugation, parasitic mycelium and formation of clamp connections, and development of teliospores in the host tissue have been studied. The fungus possesses a diplobiontic rhythm of life cycle, which is well adapted for its effective dissemination and survival under the ecological conditions to which the host is subjected.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796592

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Two cell lines with 6 and 16 chromosomes were obtained from a predominantly diploid (2n=4) suspension culture ofHaplopappus gracilis(Nutt.) Gray. The 6-chromosome line had two normal homologues of each of the twoH. gracilischromosomes; the remaining chromosome I had a deletion in the short arm, while the remaining chromosome II had a translocated piece of chromatin on the short arm forming a larger satellite than normal. The karyotypic composition of the 4- and the 6-chromosome lines remained fairly stable during thein vitroculture. In the 16-chromosome line, however, a dominant karyotype with 13 chromosomes evolved during thein vitrocultivation. Loss of chromosome(s) by fragmentation appears to be the major method of the production of aneuploid cells. Selection was found to be ‘conservative’ in the 4- and the 6-chromosome lines, while the 16-chromosome showed a ‘progressive’ selection.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796593

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Cytogenetic behaviour of suspension cultures ofHaplopappus raveniiJack, and a hybrid betweenH. gracilis(Nutt.) Gray andH. raveniimaintained in B5 medium containing 4.5×10−6M 2,4-D, was studied. A selection for diploid cells was observed in the case ofH. ravenii, while in the case of the hybrid, a steady increase in the frequency of amphidiploid cells was observed. Anaphase analyses showed a number of anomalies. It is suggested that the genome ofH. gracilishas undergone a limited genetic differentiation subsequent to its origin from that ofH. ravenii.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796594

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Dans ce travail consacré à plusieurs espèces du genreCallisia(Commélinacées), la garniture chromosomique (longeur, diamètre et volume des chromosomes) a été étudiée et des analyses cytophotométriques pratiquées sur des noyaux de méristèmes radiculaires.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796595

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Gamma rays emitted by radioactive particles of Co60″, are highly mutagenic. It can not only induce gene mutation but also act as a powerful agent in chromosome and chromatid breakage. A balery plant with 53% pollen and 71% ovule sterility was obtained in the progeny grown from seeds irradiated with 15,000r. Subsequently, this plant produced fewer mature seeds. Meiotic analysis of the microsporocytes collected from this plant showed two isochromosomes, more frequently associated with a ring of four chromosomes than without it. Cytological study of the somatic metaphase, prepared from leaf sheath meristems of the same heterozygous plant revealed a few centromeric breaks adding support to the occurrence of isochromosomes.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796596

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Endosperm development prior to cell wall formation was observed in two species ofHibiscussectionFurcaria: H. costatus, a diploid, andH. acetosella, an allotetraploid. During early development of the endosperm, divisions are free-nuclear, highly synchronous, and most nuclei contain only one nucleolus each. However, just prior to initiation of wall formation, the nuclei lose their division synchrony and the number of nucleoli per nucleus increases. The endosperm is organized into an interior and an exterior region. To the exterior there are highly developed proliferations of the embryo sac wall. Adjacent to the wall there is a zone of large, elongated mitochondria. The interior of the young endosperm is filled with an intricate labyrinth of endoplasmic reticulum, interspersed with smaller, more spherical mitochondria and both free ribosomes and polysomes. Organization, development and fine structure of the endosperm is discussed in relation to its historically assumed functions.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796597

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Early development is compared in self-fertilizedHibiscus costatusand in hybridH. cos. tatus-aculeatusandH. costatus-furcellatusendosperm. Since the paternal parentsH. aculeatusandH. furcellatusare both tetraploids, fertilization of the polar nuclei ofH. costatus, a diploid, results in tetraploid endosperm. Development of the rough endoplasmic reticulum in both the hybrids was highly aberrant and was characterized by short irregular pieces which apparently arose from blebs in regions of the membrane which were devoid of ribosomes. The nuclei of the hybrids frequently contained multiple (5–30) nucleoli, even at very young stages. In comparison, selfed material generally contain only one to perhaps three nucleoli per nucleus at the age observed. Nuclei of the hybrid endosperm also frequently contained many large clumps of heterochromatin associated with the nuclear membrane. Failure of hybrid crosses of different ploidy parents is discussed in terms of recent observations.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796598

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Difficulties in evaluating the meiosis inRosahybrids were found to be due to stickiness caused by hybridization in this genus. In sticky meiosis, the form and behaviour of chromosomes are changed and dense chromatin mass of different multivalent-like configurations are formed; but in spite of this, the two divisions are often completed. The stickiness varies very much in degree, and complete stickiness to almost normal meiosis can be observed in the same plant. Though stickiness was found to be caused by physiological conditions too in other material, the observation that it was found in hybrids mostly in our studies, indicates that this phenomen in roses is a result of an interaction between the genotype and the environment.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796599

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor

摘要:

Four hypertriploid plants were obtained: two plants were found in the progeny of the primary trisomic for chromosome 4 (Robust) in the F2population of the cross between Robust x KM 200 (a short-awned mutant). The F1hybrid of Robust x zebra Colorado (zbc) and Robust x light green (lg4) contained one plant each. All the four hypertriploids studied were larger than their diploid sibs in various plant organs.

ISSN:0008-7114    

DOI:10.1080/00087114.1975.10796600

出版商:Taylor & Francis    

年代:1975

数据来源: Taylor