DIVISION OF THE GENERATIVE CELL AND LATE DEVELOPMENT IN THE MALE GAMETOPHYTE OF GINKGO BILOBA

1988 ◽  
Vol 75 (9) ◽  
pp. 1434-1442 ◽  
Author(s):  
William E. Friedman ◽  
Ernest M. Gifford
Keyword(s):  
Ginkgo Biloba ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Late Development

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.

Absence of microspore polarity, symmetric divisions and pollen cell fate in Brachiaria decumbens (Gramineae)

Genome ◽  
2003 ◽  
Vol 46 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Roberto Gargione Junqueira Filho ◽  
Andréa Beatriz Mendes-Bonato ◽  
Maria Suely Pagliarini ◽  
Nilton Cesar Pires Bione ◽  
Cacilda Borges do Valle ◽  
...  
Keyword(s):  
Cell Fate ◽  
Nuclear Polarization ◽  
Male Gametophyte ◽  
Chromatin Condensation ◽  
Generative Cell ◽  
Pollen Grains ◽  
Pollen Mitosis ◽  
Male Sterile ◽  
Brachiaria Decumbens ◽  
Pollen Cell

Meiotic division and male gametophyte development were analyzed in one tetraploid (2n = 4x = 36) accession of Brachiaria decumbens cv. Basilisk that showed some pollen sterility. Meiotic process was typical of polyploids in that it consisted of multiple chromosome associations. Precocious chromosome migration to the poles, laggards, and micronucleus formation were abundant in both meiosis I and II and resulted in tetrads with micronuclei. After callose dissolution, microspores were released into the anther locule and had the semblance of being normal. Although each microspore initiated its differentiation by pollen mitosis, in 43.24% of the microspores, nuclear polarization was not observed and the typical hemispherical cell plate was not detected. Division was symmetric and microspores lacked differentiation between the vegetative and the generative cell. Both nuclei were of equal size, presented equal chromatin condensation, and had a spherical shape. After the first pollen mitosis and cytokinesis, each cell underwent a new symmetric mitosis without nuclear polarization. At the end of the second pollen mitosis, four equal nuclei were observed in each pollen grain. After the second cytokinesis, the cells gave rise to four equal-sized pollen grains with a similar tetrad configuration that initially remained together. Sterile pollen grains resulted from abnormal pollen mitosis. This anomaly may be explained by a mutation, probably affecting microtubule cytoskeleton formation. The importance of this male-sterile mutation for Brachiaria breeding programs is discussed.Key words: Brachiaria decumbens, male sterility, pollen mitosis, microspore polarity, symmetric division, pollen cell fate, grasses.

scholarly journals Intracellular motility and the evolution of the actin cytoskeleton during development of the male gametophyte of wheat ( Triticum aestivum L.)

1997 ◽  
Vol 352 (1364) ◽  
pp. 1985-1993 ◽  
Author(s):  
J. Heslop-Harrison ◽  
Y. Heslop-Harrison
Keyword(s):  
Actin Cytoskeleton ◽  
Vegetative Cell ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Triticum Aestivum L ◽  
Starch Accumulation ◽  
Vegetative Nucleus ◽  
Published Evidence ◽  
Main Period ◽  
Actin Mrna

The uniaperturate pollen of wheat is dispersed in a partially hydrated condition. Amyloplasts are concentrated in the apertural hemisphere where they surround the two sperms, while vigorously moving polysaccharide–containing wall precursor bodies (P–particles) together with the vegetative nucleus occupy the other. This disposition is the product of a post–meiotic developmental sequence apparently peculiar to the grasses. During vacuolation of the spore after release from the tetrad, the nucleus is displaced to the pole of the cell opposite the site of the germination aperture, already defined in the tetrad. Following pollen mitosis, the vegetative nucleus migrates along the wall of the vegetative cell towards the aperture, leaving the generative cell at the opposite pole isolated by a callose wall. As the vacuole is resorbed, the generative cell rounds up, loses its wall and follows the vegetative nucleus, passing along the wall of the vegetative cell towards the aperture where it eventually divides to produce the two sperms. Throughout this period of nucleus and cell manoeuvrings, minor inclusions of the vegetative cell cytoplasm, including mitochondria, lipid globuli and developing amyloplasts, move randomly. Coordinated vectorial movement begins after the main period of starch accumulation, when the amyloplasts migrate individually into the apertural hemisphere of the grain, a final redistribution betokening the attainment of germinability. In the present paper we correlate aspects of the evolution of the actin cytoskeleton with these events in the developing grain, and relate the observations to published evidence from another monocotyledonous species concerning the timing of the expression of actin genes during male gametophyte development, as revealed in the synthesis of actin mRNA.

scholarly journals Translocation of the generative cell towards the centre of the pollen grain due to changes in the vacuolar system in Ranunculus repens L.

2015 ◽  
Vol 42 (2) ◽  
pp. 295-300 ◽  
Author(s):  
Maria Charzyńska
Keyword(s):  
Light Microscope ◽  
Male Gametophyte ◽  
Generative Cell ◽  
Pollen Grain ◽  
Vegetative Cells ◽  
Vacuolar System

On the basis of observations performed under the light microscope on the development of the male gametophyte of <i>Ranunculus repens</i> L., the hypothesis is advanced that the translocation of the generative cell from a position adjacent to the wall towards the centre of the pollen grain, associated with change in the shape of this cell, is the result of vacuolization of the generative and vegetative cells and the interaction of these two vacuole systems.

Pollen germination of Tsuga heterophylla in vitro

1971 ◽  
Vol 49 (1) ◽  
pp. 117-119 ◽  
Author(s):  
RongHui Ho ◽  
Oscar Sziklai
Keyword(s):  
Male Gametophyte ◽  
Generative Cell ◽  
Calcium Nitrate ◽  
Pollen Grains ◽  
Potassium Nitrate ◽  
Tsuga Heterophylla ◽  
The Body ◽  
Stalk Cell

The development of the male gametophyte from western hemlock (Tsuga heterophylla (Raf.) Sarg.) pollen was complete after 5 days of incubation. This normally takes at least 6 weeks in vivo. The pollen was cultured in a solution containing boron, calcium nitrate, magnesium sulfate, and potassium nitrate. In 2 days the generative cell divided into the body cell and the stalk cell and after a further 3 days the body nucleus divided into two sperm nuclei. Morphological descriptions and measurements of the germinating pollen grains were made.

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