摘要:

Negli ovociti diPlanorbis corneus, durante il loro accrescimento (previtellogenesi e vitellogenesi), ad un nucleolo iniziale se ne aggiungono man mano degli altri. Le manifestazioni di ciascuno di essi, in rapporto anche alle variabili dimensioni che possono essere raggiunte, sono eguali. Dal lato strutturale, mentre nei nucleoli più piccoli non si hanno granuli rifrangenti (nucleolini), in quelli man mano più sviluppati appaiono aumentare sensibilmente di numero. Per lo stato fisico ad una condizione dei nucleoli di maggiore densità, indicata dall'affinità per il rosso del Mallory, subentra quindi una minore densità, indicata dall'affinità per l'azzurro dello stesso metodo. Nel contempo ciascun nucleolo presenta, nella fase iniziale del suo sviluppo, una scarsa quantità di ARN, di polisaccaridi e di tiogruppi, in una successiva, fino al completamento della vitellogenesi, un aumento sensibile degli stessi composti, ed infine una diminuzione marcata di essi man mano che si completa la vitellogenesi.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796038

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

1.Treatment of inflorescences of the wheat variety N.P. 809 just prior to the onset of meiosis gave rise to several haploids (2n= 21) in the progeny. When the inflorescences were given a subsequent dose of X-rays after the emergence of the ear, several twin seedlings and a triplet arose in the progeny.2.Meiosis was studied in the microsporocytes of three different haploid plants. At pachytene, a few bivalents revealed associations at specific knob like intercalary regions or at the distal ends. A maximum frequency of 5 bivalents was found in one haploid plant. Various types of secondary associations were found both among univalents and bivalents and the incidence of such associations was found to decrease with an increase in bivalent frequency. It is suggested from the behaviour of the satellited univalents that all such associations arise from attractions in specific regions of the chromosomes.3.Multivalent associations were observed during meiosis in the twin and triplet plants. Nearly 50% of all the chromosomes formed multivalent associations in the triplet. The highest association observed was a decavalent; octavalents were frequent.4.The progenies of the haploids, twins and triplet had variable chromosome numbers and plant and ear characteristics. A high degree of karotype re-patterening occurs in them. A greater incidence of cytological and morphological changes was observed in the progeny of the triplet in comparison with those of the haploids.5.Most morphological abnormalities in bread wheat can be correlated with whole chromosome or segmental aneuploidy.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796039

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

The paper deals with the mutual relation of the nucleole in sex differentiation in various sex forms of hemp (Cannabis sativaL.). The genotype divergencies of the different sex forms are expressed in the size of the nucleoles both in pollen mother cells as also in the nucleoles of young pollen grains. Results of the measurement were statistically evaluated by means of the t- test and analysis of variation. The fact that the difference in genotype is more evident in the size of the nucleoles (the differences are statistically significant) than in the size of the cell nuclei seems to prove that the nucleole in all probablity has a certain influence on the sex differentiation.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796040

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

1.The role of polyploidy in the development of seventeen species ofAlliumwas studied. It was determined that the time of occurrence of the tetraploid divisions could be correlated with the renewal of growth of the first leaf the seedling following germination.2.In section I of the genus, leaf initiation and tetraploid divisions were found to occur when the seedlings were ten to twelve millimeters long. The tetraploid divisions, however, were never very numerous.3.All the species studied belonging to section II with the exception ofA. tanguticumandA. caeruleumfollowed the same developmental pattern asA. cepareported in 1946 by Bergerand Witkus. In its developmentA. tanguticumfollows thenutanspattern of section III. The development ofA. caeruleumwas more similar to that ofA. tanguticumthan to the other species belonging to section II that were studied.4.In studying the development of species belonging to section III, it was noted that the section could be divided into two subgroups. The first subgroup would include those species with thenutanstype of development. The second subgroup on the other hand would include those species which follow the pattern of development similar toA. porrum.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796041

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

Detailed analysis of chromosomes at pachytene and later stages of meiosis were made in the five species ofSorghumbelonging to the Sub-genusEu-sorghum.Pachytene chromosomes are depicted on the basis of total length, relative length, arm ratio, amount and distribution of heterochromatin and number and position of chromomeres. The characteristics of each of the ten chromosomes in the haploid complement are described in detail in different classes bringing out the similarities and differences amongst the five species. Species have been comparedinter aliaon their total lengths of chromosomes and the differences in lengths both within the species and between them were statistically tested.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796042

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

L'Autore espone brevemente i dati emersi dalle prime esperienze sull'impiego della P.T.C, nella psoriasi, e ritiene probabile l'esistenza di un nesso fra il fattore P.T.C, e quello responsabile della malattia.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796043

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

Meiotic studies have been made in nine species of the genusAdiantum.Some of them likeA. caudatum, A. philippense, A. capillus-venerisandA. aethiopicumwere collected from several localities where they were found growing in nature. Others were procured from different nurseries of India.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796044

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

Cytogenetical studies were undertaken in two interspecific hybrids ofSetcreasea purpurea×S. pallida.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796045

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor

摘要:

A study of the mitotic behaviour of chromosomes of the different species and varieties ofAglaonemaandRichardiahas been presented in the paper. The Indian forms investigated areA. hospitum, A. costatum, A. costatum, var.‘foxi’andR. Elliottianashowing 38, 40, 48 and 32 respectively as the normal chromosome numbers. The high number of chromosomes ofAglaonemasuggests their polyploid constitution. Numerical differences maintained both at an intra- and interspecific levels clearly indicate their distinct relationship.

ISSN:0008-7114    

DOI:10.1080/00087114.1961.10796046

出版商:Taylor & Francis    

年代:1961

数据来源: Taylor