摘要:

È stata studiata la maturazione dei testicoli dei maschi diDaphnia magnastabilendo come tappe di sviluppo le mute con le quali l'animale acquisisce lo stato adulto. Alla nascita i testicoli contengono solo spermatogoni in riposo; alla prima muta essi sono in intensa attività mitotica; alla seconda muta si notano spermatociti di primo ordine in meiosi; alla terza muta il processo spermatogenetico è arrivato fino allo stadio di spermatidio e infine alla quarta muta l'animale raggiunge la maturità sessuale con i testicoli pieni di spenni.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796153

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

Some of the ultrastructural modifications which occur during meiotic prophase I in three hybrids ofDendrobiumorchids have been examined by electron microscopy. In early prophase I the enlarged nucleus has no annulate pores in its envelope. The onset of nuclear break down is evidenced by the reappearance of pore-like discontinuities in a small region of the envelope. During this stage the chromosomes exhibit synaptinemal complexes. Continued nuclear envelope destruction occurs as the number of pores increases with new pores being formed in regions of the envelope adjacent to those pores already present. Initially, the cytoplasmic organelles are distributed throughout the megasporocyte. Subsequently they are concentrated in the perinuclear cytoplasm and with the progressive break down of the nucleus all the membrane-bound organelles of the megasporocyte are degenerated. It is proposed that marked decrease in all cytoplasmic components during prophase I accounts for the increase in numbers of phragmosomes which may be formed by the coalescence of degraded organelles. Very few identifiable organelles remain in meiotic metaphase I; however, mitotic metaphase figures in proliferating integument exhibit no comparable organelle destruction. Several persisting ultrastructural features of the megasporocyte which are described in earlier studies are also mentioned. These include the presence of rhopheocytosis, lipid micro-droplets, and small Golgi-apparati; and the absence of intercellular plasmodesmata. Developmental patterns are established and discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796154

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

The cytology of 189 collections comprising 131 species of Compositae from N. India has been worked ont. Sixteen genera cytologically investigated for the first time are:Dichrocephala, Cyathocline, Myriactis, Rhynchospermum, Blumea, Laggera, Ifloga, Caesulia, Vicoa, Carpesium, Siegesbeckia, Blainvillea, Lasthenia, Tricholepis, Volutarella, and Pterotheca.New chromosome counts are made available for 57 species.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796155

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

The comparative effects of colchicine in combination with 11 chemicals (1 paradichlorobenzene, 2 coumarine, 3 saponin, 4 α-bromonapthalene, 5 phloroglucinol, 6 8-hydroxy-quinoline, 7 gammexane, 8 aesculine, 9 acenapthene, 10 β-bromonapthol and 1l phenol) on the production of polyploid cells inTrigonella foenum-graecumhas been studied. In the chemicals alone in comparison to water the root growth has been accelerated in (1), (7) and (9) while (5) shows no change and in the rest there is a decrease. In Combination with colchicine every chemical shows decrease except in (3), and 10. The frequency of metaphase plates per root tip is lowest in water while it reaches the maximum in (3) followed by (4), (8), (5), (7), (6), (9), (1), (10) and colchicine in decending order. In combination with colchicine the accumulation of metaphase plates increases in (1) while in the rest there is a decrease. The rate of root growth and karyokinetic activity are not interrelated to each other. There is some correlation between frequency of chromosomal aberrations and retardation of growth rate of roots.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796156

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

The present communication deals with the cytology of 21 taxa (16 well recognized species) belonging to 6 genera, namelyPteris, Coniogramme, Cheilanthes, Onychium, AnogrammaandAdiantum, of W. Himalayan Adiantaceae, sensu ALSTON. All the reports from Dalhousie hills are fresh records (cf. Table I). This data have revealed at least 6 new species-complexes, namelyPteris cretica, Onychium contiguum, Adiantum edgeworthii. A. venustum, Cheilanthes albomarginataandCheilanthes farinosa.The cytotypes are associated either with polyploidy or aneuploids are recorded at the diploid level (cf. Table II).

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796157

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

Chromosome numbers in twenty one fern species from Kodaikanal, South India are reported. Out of these 12 are diploids, one triploid apogamous and 8 tetraploids. Comparisons have been made with earlier reports from other regions.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796158

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

An assessment of the temperature sensitivity of chromosomes inTriticum monococcumhas been made with a view to evaluating the adaptability of the diploid wheat to temperature- conditioned environments. Since stability of chromosomal mechanisms and fertility provide important criteria in relation to such adaptation, these were employed for obtaining a measure of temperature sensitivity. The various durations of high temperature treatment were found to affect sporogenesis in the pollen mother cells in many ways; the more important chromosomal irregularities included differential condensation, disturbed metaphase arrangement, desynapsis, degeneration of chromatin material, and irregular anaphase distribution of chromosomes leading to the formation of micronuclei. Observations revealT. monococcumto be very sensitive to high temperature conditions.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796159

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

Cytogenetical studies were undertaken inSetcreasea brevifolia,S. purpureaand in their eight interspecific hybrids.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796160

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

1.Meiotic chromosomes of seven species of the genusRubus(x=7), two species ofSpiraea(x=18) and one species ofPotentilla(x=28) have been studied (vide Table 1).2.SpiraeaandPotentillaspecies are tetraploid and octaploid respectivelly while all of the species ofRubusare diploid.3.Extranuclear bodies are seen in some species ofRubusand are non-chromatic.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796161

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor

摘要:

L'Autore ha sperimentato la sensibilità umana al test olfattivo GR (soluzione standard di geraniolo) mettendone in luce le caratteristiche ed il comportamento genetico.

ISSN:0008-7114    

DOI:10.1080/00087114.1965.10796162

出版商:Taylor & Francis    

年代:1965

数据来源: Taylor