The formation of the generative cell in Polystachia pubescens (Orchidaceae)

1992 ◽  
Vol 5 (2) ◽  
Author(s):  
M. Schlag ◽  
M. Hesse
Keyword(s):  
Generative Cell

The development of the male gametophyte and spermatogenesis in Taxus baccata L

1986 ◽  
Vol 228 (1250) ◽  
pp. 85-96 ◽  
Keyword(s):  
Pollen Tube ◽  
De Novo ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Equal Size ◽  
Taxus Baccata ◽  
Transverse Wall ◽  
Proximal Pole ◽  
Spermatogenous Cell ◽  
Tube Cell

The development of the male gametophyte of Taxus baccata has been studied over a period of 20 weeks, from germination of the microspore in February to spermatogenesis in July. A few days after germination the microspore nucleus divides and a transverse wall forms at the equator cutting off the small generative cell and a large tube cell. The latter immediately begins to expand to form the pollen tube. The first division thus establishes the polarity of the gametophyte and the generative cell is regarded as proximal. The transverse wall is ephemeral, and within six weeks it has disappeared. The nucleus of the generative cell divides while still at the proximal pole. The two daughter nuclei are unequal in size, but they remain associated and together move distally. The larger nucleus eventually becomes the nucleus of the spermatogenous cell, and the smaller the sterile nucleus. The spermatogenous cell acquires a distinctive cytoplasm and becomes surrounded by a wall which arises de novo . The nucleus of the spermatogenous cell enlarges, but always remains towards one side of the cell so that at mitosis the spindle is contained within one hemisphere. After division the wall of the spermatogenous cell is ruptured and the two sperms are released as naked nuclei of equal size. The cytoplasm of the spermatogenous cell degenerates as it enters the tube, but remains recognizable until fertilization.

Fusion studies of pollen protoplasts and generative cell protoplasts in Lilium longiflorum

Plant Science ◽  
1990 ◽  
Vol 72 (2) ◽  
pp. 259-266 ◽  
Author(s):  
Kenji Ueda ◽  
Yoshihisa Miyamoto ◽  
Ichiro Tanaka
Keyword(s):  
Generative Cell ◽  
Lilium Longiflorum

scholarly journals Prunus necrotic ringspot virus Early Invasion and Its Effects on Apricot Pollen Grain Performance

2007 ◽  
Vol 97 (8) ◽  
pp. 892-899 ◽  
Author(s):  
Khalid Amari ◽  
Lorenzo Burgos ◽  
Vicente Pallas ◽  
María Amelia Sanchez-Pina
Keyword(s):  
Developmental Stages ◽  
Generative Cell ◽  
Pollen Grains ◽  
Growth Zone ◽  
Pollen Tubes ◽  
Climatic Conditions ◽  
Pollen Grain ◽  
Ringspot Virus ◽  
Prunus Necrotic Ringspot Virus

The route of infection and the pattern of distribution of Prunus necrotic ringspot virus (PNRSV) in apricot pollen were studied. PNRSV was detected both within and on the surface of infected pollen grains. The virus invaded pollen during its early developmental stages, being detected in pollen mother cells. It was distributed uniformly within the cytoplasm of uni- and bicellular pollen grains and infected the generative cell. In mature pollen grains, characterized by their triangular shape, the virus was located mainly at the apertures, suggesting that PNRSV distribution follows the same pattern as the cellular components required for pollen tube germination and cell wall tube synthesis. PNRSV also was localized inside pollen tubes, especially in the growth zone. In vitro experiments demonstrated that infection with PNRSV decreases the germination percentage of pollen grains by more than half and delays the growth of pollen tubes by ≈24 h. However, although PNRSV infection affected apricot pollen grain performance during germination, the presence of the virus did not completely prevent fertilization, because the infected apricot pollen tubes, once germinated, were able to reach the apricot embryo sacs, which, in the climatic conditions of southeastern Spain, mature later than in other climates. Thus, infected pollen still could play an important role in the vertical transmission of PNRSV in apricot.

scholarly journals Immunochemical and immunocytochemical identification of a myosin heavy chain polypeptide in Nicotiana pollen tubes

1989 ◽  
Vol 92 (4) ◽  
pp. 569-574
Author(s):  
X.J. Tang ◽  
P.K. Hepler ◽  
S.P. Scordilis
Keyword(s):  
Pollen Tube ◽  
Nuclear Envelope ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Immunofluorescence Microscopy ◽  
Generative Cell ◽  
Pollen Tubes ◽  
Nuclear Surface ◽  
Common Pattern ◽  
Western Blots

A myosin heavy chain polypeptide has been identified and localized in Nicotiana pollen tubes using monoclonal anti-myosin antibodies. The epitopes of these antibodies were found to reside on the myosin heavy chain head and rod portion and were, therefore, designated anti-S-1 (myosin S-1) and anti-LMM (light meromyosin). On Western blots of the total soluble pollen tube proteins, both anti-S-1 and anti-LMM label a polypeptide of approximately 175,000 Mr. Immunofluorescence microscopy shows that both antibodies yield numerous fluorescent spots throughout the whole length of the tube, often with an enrichment in the tube tip. These fluorescent spots are thought to represent vesicles and/or organelles in the pollen tubes. In addition to this common pattern, anti-S-1 stains both the generative cell and the vegetative nuclear envelope. The different staining patterns of the nucleus between anti-S-1 and anti-LMM may be caused by some organization and/or anchorage state of the myosin molecules on the nuclear surface that differs from those on the vesicles and/or organelles.

scholarly journals Autoradiographic studies of DNA and histone synthesis in successive differentiation stages of pollen grain in Hyacinthus orientalis L.

2014 ◽  
Vol 50 (3) ◽  
pp. 367-380 ◽  
Author(s):  
Elżbieta Bednarska
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Vegetative Cell ◽  
Developmental Stages ◽  
Generative Cell ◽  
Pollen Grain ◽  
Cell Nuclei ◽  
Hyacinthus Orientalis ◽  
Histone Synthesis ◽  
Generative Cells

DNA and histone synthesis in five consecutive morphological stages of <em>Hyacinthus orientalis</em> L. pollen grain differentiation were studied autoradiographically. DNA synthesis was found to occur in both the generative and the vegetative cell. DNA replication in the generative cell took place when the generative cell was still adhered to the pollen grain wall but already devoid of callose wall. DNA synthesis in the generative cell slightly preceded that in the vegetative cell. Histones were synthesized in phase S of the generative and vegetative cell. In the generative cell histone synthesis also continued at a lower level after completion of DNA replication. In the developmental stages under study the nuclei of the generative cells were decidedly richer in lysine histones than vegetative cell nuclei.

scholarly journals Tradescantia bracteata pollen in vitro: pollen tubes development and mitosis

2015 ◽  
Vol 46 (4) ◽  
pp. 587-598 ◽  
Author(s):  
E. Lewandowska ◽  
M. Charzyńska
Keyword(s):  
Pollen Tube ◽  
Generative Cell ◽  
Metaphase Plate ◽  
Pollen Grains ◽  
Neutral Red ◽  
Generative Nucleus ◽  
Mitotic Spindles ◽  
Germinating Pollen ◽  
Vacuolar System

About 90 per cent of <i>Tradescantia bracteata</i> pollen germinates <i>in vitro</i> after 15 min. Mitosis starts in the pollen tube after about 3 h. The mitotic trans-formations of chromosomes within the generative nucleus are not synchronized. They involve succesively the linearly arranged chromosomes in the elongated generative nucleus. In metaphase the chromosomes are arranged tandem-like linearly along the pollen tube. The chromatides translocate in anaphase from various distances to the poles in a plane parallel to the metaphase plate. This suggests that chromosomes have individual mitotic spindles and that coordination of the chromosome transformations in the generative cell is much less strict than in a typical somatic mitosis. Starch is the storage material of pollen grains. In the vegetative cytoplasm of mature pollen grains minute reddish-orange vesicular structures are visible after staining with neutral red. They do not fuse with the vacuoles proper arising in germinating pollen grains to form the vacuolar system of the pollen tube.

scholarly journals snRNP: Rich Nuclear Bodies inHyacinthus orientalisL. Microspores and Developing Pollen Cells

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
K. Zienkiewicz ◽  
E. Bednarska
Keyword(s):  
Pollen Development ◽  
Rna Synthesis ◽  
Generative Cell ◽  
Pollen Grains ◽  
Strong Relationship ◽  
Nuclear Bodies ◽  
Cajal Body ◽  
Sm Proteins ◽  
Hyacinthus Orientalis

The aim of the present work was the characterization of nuclear bodies in the microspore and developing pollen cells ofHyacinthus orientalisL.. The combination of Ag-NOR, immunofluorescence and immunogold techniques was used in this study. The obtained results showed the presence of highly agyrophylic extranucleolar bodies in microspore and developing pollen cells, which were finally identified as Cajal bodies. In all cases, a strong accumulation of snRNP-indicating molecules including TMG cap, Sm proteins and U2 snRNA, was observed in the examined nuclear bodies. In contrast to their number the size of the identified structures did not change significantly during pollen development. In the microspore and the vegetative cell of pollen grains CBs were more numerous than in the generative cell. At later stages of pollen development, a drastic decrease in CB number was observed and, just before anthesis, a complete lack of these structures was indicated in both pollen nuclei. On the basis of these results, as well as our previous studies, we postulate a strong relationship between Cajal body numbers and the levels of RNA synthesis and splicing machinery elements in microspore and developing pollen cells.

Basal body loss during fungal zoospore encystment: evidence against centriole autonomy

1986 ◽  
Vol 83 (1) ◽  
pp. 135-140
Author(s):  
I.B. Heath ◽  
S.G. Kaminskyj ◽  
T. Bauchop
Keyword(s):  
Life Cycle ◽  
Cell Line ◽  
Basal Body ◽  
Generative Cell ◽  
Basal Bodies ◽  
Cilia And Flagella ◽  
Endosymbiotic Origin

The controversial question of the possible autonomy of centrioles, as shown by the persistence of all or part of them in the generative cell line throughout the life cycle of organisms, remains unresolved. All previous reports on shedding or withdrawal of cilia and flagella showed that their basal bodies (= centrioles) were retained in the cells where they may, or may not, subsequently disassemble. We show that in the fungus Neocallimastix sp. the basal bodies are discarded with the flagella when zoospores encyst. This shedding of basal bodies argues against centriolar persistence in any form and thus against their autonomy and endosymbiotic origin.

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