摘要:

Two successive stages — nucellar and archesporial — of ovule development in three hybrids ofDendrobiumorchids have been studied by electron microscopy. A megaspore mother cell is developed at the tip of each placental outgrowth following a 30-day mitotic period induced by pollination. Except for its terminal position in the nucellar row, the potential megaspore mother cell exhibits no unique morphological properties. It is proposed that the marked multiplication of organelles effecting cytoplasmic growth in the archesporial phase is facilitated through a net absorption of cytoplasm from the surrounding nutritive cells by the developing megaspore mother cell. Evidence for this is presented by the concomitant loss of plasmodesmata and the initiation of rhopheocytosis between the developing cell and the adjacent nucellar and epidermal cells and a marked reduction in the concentration of ribonucleoprotein particles within the developing cell. No evidence can be found that the simple Golgi-apparati of the archesporial cell elaborate either the numerous single-membrane-bound vesicles of the cytoplasm or the extensive, continuous network of the cell endoplasm. Furthermore, no evidence can be found to support the theory that mitochondria and plastids share a common origin or that their origins arede novo.Cup-proliferation and binary fission are the methods by which they are duplicated in the developing archesporial cell. Cytoplasmic lipid microdroplets are also described and discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796128

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796129

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

Viene confermato in 28 il numero dei cromosomi del corredo diploide diDiscoglossus pictus; questa specie presenta eterogametia femminile, mostrando la ♀ un paio di omologhi diversi tra loro per lunghezza.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796130

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

On the basis of observations of cells (strains KB-PK and L-fibroblasts) cultivated in tissue culturesin vitrothe author believes nuclear rotation to be an active and pantypical phenomenon. He believes, however, that, with regard to the fact that the nuclei of one and the same culture do not move at the same time, in the same direction and at the same speed the inhibition of this phenomenon cannot be used as a criterion of the reaction of the cells on some noxae before it is studied more deeply. In his opinion, the rotation is in relation to the elimination of products from the nucleolus into the cytoplasm.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796131

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

Sono stati esaminati, con la tecnica delle culture dei tessuti, i cromosomi somatici diRhinolophus ferrumequinum(Sehr.) e diRhinolophus euryaleBlasius.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796132

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

Le paraaminosalicylate d'isonicotinylhydrazide (PASINH) manifeste au moment de la mitose une triple action:1°)gélatinisation et collage des chromosomes,2°)ruptures chromosomiques, et3°)troubles de l'appareil achromatique. Les relations entre ces divers effets étant discutées, ces trois actions semblent largement indépendantes.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796133

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796134

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

Vengono descritti particolari organuli osservati nei parenchimi di riserva di tuberi diHelianthus tuberosusposti ad inverdire e nei parenchimi clorofilliani di foglie diPetunia hybrida.Questi organuli — che sono da noi denominati provvisoriamente «proteosomi» — hanno dimensioni circa uguali a quelle dei mitocondri, sono delimitati da una evidente doppia membrana e contengono nel loro interno una sostanza fondamentale omogenea, più o meno opaca ai raggi elettronici, nella quale spicca un corpo cristallino voluminoso, costituito da numerosi cristallini elementari disposti su più file, dal periodo di circa 150 Å. I proteosomi, per questi caratteri e per il fatto di non sottostare ad ulteriore evoluzione, se assomigliano ad alcuni organuli descritti recentemente inDaturae inPisum, si differenziano nettamente sia da altri aggregati cristallini, privi di membrana (virus), sia dai proteoplasti.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796135

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

By treating the bean radicles at 4° for 3 to 6 hours, a high frequency of prometaphase cells was accumulated. On the other hand, the frequencies of metaphase, anaphase and telophase were decreased to zero. The increase or decrease in the frequencies of different phases of mitotic division was a linear function of the duration of low temperature treatment.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796136

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor

摘要:

L'Autore descrive un metodo di determinazione del cariotipo, dai tessuti ovulari, che almeno inScilla autumnalis(Liliaceae) fornisce risultati del tutto simili a quelli ottenuti utilizzando i meristemi dell'apice radicale.

ISSN:0008-7114    

DOI:10.1080/00087114.1964.10796137

出版商:Taylor & Francis    

年代:1964

数据来源: Taylor