An ultrastructural study of pollen development in tomato (Lycopersicon esculentum). II. Pollen maturation

1993 ◽  
Vol 71 (8) ◽  
pp. 1048-1055 ◽  
Author(s):  
P. L. Polowick ◽  
V. K. Sawhney
Keyword(s):  
Lycopersicon Esculentum ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grains ◽  
Mature Pollen ◽  
Ultrastructural Changes ◽  
Second Phase ◽  
Cell Cytoplasm ◽  
Pollen Maturation

The maturation of tomato pollen grains encompassed several ultrastructural changes. The generative cell separated from the intine and was free in the cytoplasm of the vegetative cell. This process coincided with the appearance of starch in plastids and the division of elongated mitochondria. This stage was followed by a second phase of vacuolation in the vegetative cell cytoplasm. Starch was still abundant at this stage, as were mitochondria, endoplasmic reticulum (ER), and ribosomes. Lipid droplets were the prominent feature of mature pollen grains. Each droplet was surrounded by rough ER (RER), suggesting the role of RER in lipid accumulation and mobilization. Long stretches of ER were present at early stages of maturation, and stacks of up to 50 strands of RER were abundant in mature pollen. The plastids in mature pollen were devoid of starch and had few internal membranes. Mitochondria were abundant and spherical with parallel cristae. In many cases, the cytoplasm at the periphery of the mature pollen grain was dense, forming a distinct zone, and contained only ER. The generative cell cytoplasm had mitochondria, ER, and actin-like filaments but no plastids. The pollen wall at maturity had a lamellated foot layer, a lightly sculptured tectum, and broad intine. The intine was layered in the region of the pollen aperture. Key words: Lycopersicon esculentum, pollen grains, tomato, ultrastructure.

scholarly journals Ultrastructural study of maturing pollen in Arabidopsis thaliana (L.) Heynh. (Brassicaceae)

2014 ◽  
Vol 66 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Krystyna Zając
Keyword(s):  
Arabidopsis Thaliana ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Spherical Shape ◽  
Ultrastructural Changes ◽  
Lipid Bodies ◽  
Cell Cytoplasm ◽  
Cell Form ◽  
Microspore Stage ◽  
Pollen Stage

Ultrastructural changes in <em>Arabidopsis thaliana</em> pollen, between late microspore stage and mature pollen stage were described. When the generative cell was peeled off from the intine, it was of spherical shape and had all usual organelles with the exception of plastids. The cytoplasm transformation of the vegetative cell included an increase in the number of mitochondria and changes in the accumulation of starch and lipid bodies. The starch plastids were observed at the bicellular and early tricellular pollen stages and next starch was utilized during the maturation procces. The lipid bodies of the vegetative cell form a very regular sheath around the generative cell and then, around the sperm cells. Before anthesis the lipid bodies were dispersed within the whole vegetative cell cytoplasm.

Protein synthetic activity during normal pollen development and during induced pollen embryogenesis in Hyoscyamus niger

1984 ◽  
Vol 62 (12) ◽  
pp. 2493-2513 ◽  
Author(s):  
V. Raghavan
Keyword(s):  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grains ◽  
Synthetic Activity ◽  
Pollen Embryogenesis ◽  
Starch Accumulation ◽  
Hyoscyamus Niger ◽  
Amino Acid Incorporation ◽  
Pollen Maturation ◽  
Germinating Pollen

Protein synthetic activity during maturation, germination, and embryogenic phases of pollen grains of Hyoscyamus niger (L.) was investigated by means of autoradiography of incorporation of [3H]arginine, [3H]leucine, [3H]lysine, and [3H]tryptophan. Silver grain counts showed that during pollen maturation, peaks of incorporation of [3H]arginine and [3H]lysine occurred before the onset of vacuolation in the uninucleate pollen grains and as starch accumulation was initiated in the bicellular pollen grains. In the latter, labeled amino acids were mostly incorporated into the vegetative cell and very little appeared in the generative cell. [3H]leucine and [3H]tryptophan were not incorporated into uninucleate pollen grains at any stage of their development, although they were localized in the vegetative cell of bicellular pollen grains. In germinating pollen grains the nucleus of the vegetative cell, the generative cell, and sperms did not incorporate the isotopes. While the majority of pollen grains incorporated [3H]arginine, [3H]leucine, [3H]lysine, and [3H]tryptophan immediately after culture of anthers, during further periods of culture, protein synthetic activity persisted only in a small number of uninucleate, nonvacuolate, and densely staining "embryogenically determined" pollen grains confined to the periphery of the anther locule. Subsequent division of these pollen grains was accompanied by incorporation of [3H]arginine, [3H]leucine, and [3H]lysine into the vegetative cell or into both the vegetative cell and generative cell. It is suggested that, in contrast to the 3H-labeled amino acid incorporation pattern observed in pollen grains during their normal ontogeny, a significant change associated with embryogenic induction is the incorporation of [3H]leucine and [3H]tryptophan into embryogenically determined uninucleate pollen grains and of [3H]arginine, [3H]leucine, and [3H]lysine into the generative cell of bicellular pollen grains.

Development of sperm cells in barley

1975 ◽  
Vol 53 (10) ◽  
pp. 1051-1062 ◽  
Author(s):  
David D. Cass ◽  
Ilana Karas
Keyword(s):  
Cell Membrane ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grains ◽  
Complete Separation ◽  
Pollen Wall ◽  
Vegetative Nucleus ◽  
Sperm Cells ◽  
Subsequent Stage ◽  
Microspore Stage

Ultrastructural events in barley sperm development were examined from the uninucleate microspore stage to establishment of two mature sperm cells in pollen grains. Microspore mitosis produces a vegetative nucleus and a naked generative cell, both embedded in vegetative cell cytoplasm. The generative cell membrane is enclosed by vegetative cell membrane. The generative cell, at first apparently unattached, becomes attached to the pollen wall and acquires a cell wall by centripetal vesicle accumulation. Wall formation may be complete at the time of generative cell karyokinesis; karyokinesis occurs while the generative cell is attached to the pollen wall. Cytokinesis of the generative cell is delayed. The subsequent stage is a binucleate, attached generative cell with a wall. Generative cell cytokinesis appears to involve formation of a partition between the two sperm nuclei. Eventual complete separation of the sperm cells occurs only after the two-celled derivative of the generative cell detaches from the pollen wall. Final stages in sperm cell separation are considered to result from degradation of the partitioning and surrounding wall, not from furrowing of a naked binucleate generative cell according to previous suggestions. Mature plastids were not observed in the generative cell or the sperms.

Pollen exine substructure In Fagus (Fagaceae): role of tufts in exine expansion

1990 ◽  
Vol 68 (10) ◽  
pp. 2195-2200 ◽  
Author(s):  
Don Claugher ◽  
John R. Rowley
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Pollen Grains ◽  
Mature Pollen ◽  
Similar Range ◽  
Fagus Sylvatica L ◽  
Microscopy Images ◽  
Scanning Electron

We compare results obtained from mature pollen of Fagus sylvatica L. using high-resolution scanning electron microscopy with fransmission electron microscopy images from several stages, from the early free microspore through to mature pollen grains. Exine processes (tufts) on young and mature grains are rodlike, with cross striations 10–15 nm wide. The total diameter of the tufts is 70–100 nm on exines of young microspores and up to 200–250 nm on mature exines. Tufts about 70 nm wide on the young microspores contain about five stacks of loops about 30 nm in diameter, whereas larger tufts on more mature exines have many stacks of the 30 nm wide loops. At maturity there is a mixture of large (200–250 nm wide) and small (70–100 nm wide) tufts and some tapering down from over 200 nm in width to less than 100 nm. There is continuity and a similar range of widths between the tufts as they occur as bacules and components of the tectum. We conclude that either new large-sized tufts are inserted during growth or some of the small (original sized) tufts increase in diameter from their bases toward the outer tip, or that both of these processes occur.

scholarly journals Influence of change in the proportion of H1 histone variants on microsporogenesis and development of male gametophyte in transgenic plants of tobacco (Nicotiana tabacum L.)

2011 ◽  
Vol 72 (1) ◽  
pp. 25-35 ◽  
Author(s):  
Joanna Ślusarczyk ◽  
Andrzej Wierzbicki ◽  
Marcin Przewłoka ◽  
Teresa Tykarska ◽  
Andrzej Jerzmanowski ◽  
...  
Keyword(s):  
Male Gametophyte ◽  
Pollen Grains ◽  
Histone Variants ◽  
Ultrastructural Changes ◽  
Control Group ◽  
H1 Histone ◽  
Nicotiana Tabacum L ◽  
Sterile Pollen ◽  
Different Levels

As continuation of investigations in to the mechanism of the role of the H1 histone, which is a crucial protein component chromosomes of all eukaryotes, transgenic tobacco plants with different levels of the H1 histone variants were examined. Tobacco has six sequential variants of the H1 histone: two major ones (H1A and H1B), constituting ca. 90% of all H1, and four minor ones (H1C, H1D, H1E and H1F), occurring in very small quantities. The following groups of plants were examined: K - control group with a full set of histone variants; -AB -with the A and B variants removed; -ABCD - with the A, B, C and D variants removed; and -CD - with the C and D variants removed. The analysis of microsporogenesis in those plants, based on preparations squeezed in acetoorcein, revealed the asynchronous course of meiosis in -AB and -ABCD plants, occurrence of chromosomal aberration, and, consequently, the formation of sterile pollen grains (accordingly: 84,4% and 81,4%). In -CD plants, the percentage of aberration and sterile pollen grains was similar to the control material. Electron microscope observations of microsporogenesis showed ultrastructural changes. In -AB and -ABCD plants, a major portion of the pollen grains were degraded. The smallest number of degraded pollen grains, in comparison with the control, was found in the -CD group.

scholarly journals Ultrastructural transformations in the cytoplasm of differentiating Hyacinthus orientalis L. pollen cells

2014 ◽  
Vol 57 (2) ◽  
pp. 235-245 ◽  
Author(s):  
Elżbieta Bednarska
Keyword(s):  
Vegetative Cell ◽  
Generative Cell ◽  
Pollen Grain ◽  
Border Region ◽  
Ultrastructural Changes ◽  
Grain Development ◽  
Callose Wall ◽  
Highly Active ◽  
Hyacinthus Orientalis

The sequence of ultrastructural changes in the cytoplasm during the successive stages of pollen grain development in <em>Hyacinthus orientulis</em> pollen cells was studied. The cytoplasmic transformations of the generative cell included the elimination of plastids, increase in the number of mitochondria, assumption of a spindle shape with the aid of microtubules and the characteristic development of the vacuole system with the formation of so-called colored bodies. The cytoplasmic transformations of the generative cell encompassed changes in the plastids, which began to accumulate starch soon after the cell was formed, then released it shortly before anthesis, an increase in the number of mitochondria and an increase in the number of highly active dictyosomes just before anthesis. Changes in the structure of the border region between the differentiating pollen cells were associated mainly with the periodical appearance of a callose wall and the presence of lysosome-like bodies in the cytoplasm of the vegetative cell surrounding the generative cell. They arose soon after the disappearance of the callose wall and disappeared shortly before anthesis.

scholarly journals An L-type lectin receptor-like kinase promotes starch accumulation during rice pollen maturation

Development ◽  
2021 ◽  
pp. dev.196378
Author(s):  
Zhiyuan He ◽  
Ting Zou ◽  
Qiao Xiao ◽  
Guoqiang Yuan ◽  
Miaomiao Liu ◽  
...  
Keyword(s):  
Starch Synthesis ◽  
Pollen Grains ◽  
Starch Accumulation ◽  
Male Sterile ◽  
Pollen Maturation ◽  
Lectin Receptor ◽  
Rice Mutant ◽  
Receptor Like Kinase ◽  
Mutant Pollen

Starch accumulation is key for the maturity of rice pollen grains; however, the regulatory mechanism underlying this process remains unknown. Here, we isolated a male-sterile rice mutant, abnormal pollen 1 (ap1), which produces nonviable pollen grains with defective starch accumulation. Functional analysis revealed that AP1 encodes an active L-type lectin receptor-like kinase (L-LecRLK). AP1 is localized to the plasma membrane and its transcript is highly accumulated in pollen during the starch synthesis phase. RNA-seq and phosphoproteomic analysis revealed that the expression/phosphorylation levels of numerous genes/proteins involved in starch and sucrose metabolism pathway were significantly altered in the mutant pollen, including a known rice UDP-glucose pyrophosphorylase (OsUGP2). We further found that AP1 physically interacts with OsUGP2 to elevate its enzymatic activity likely through targeted phosphorylation. These findings revealed a novel role of L-LecRLK in controlling pollen maturity via modulating sucrose and starch metabolism.

scholarly journals Ultrastructural and metabolic transformations of differentiating Hyacinthus orientalis L, pollen grain cells. I. RNA and protein synthesis

2014 ◽  
Vol 53 (2) ◽  
pp. 145-158 ◽  
Author(s):  
Elżbieta Bednarska
Keyword(s):  
Protein Synthesis ◽  
Vegetative Cell ◽  
Generative Cell ◽  
Growth Dynamics ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Cell Protein ◽  
Replication Process ◽  
Rna And Protein Synthesis ◽  
Hyacinthus Orientalis

RNA and protein synthesis were investigated in generative and vegetative cells during maturation of pollen grains. The rate of RNA and protein synthesis was analysed in reference to the successive interphase periods of the life cycle of pollen cells as well as against the background of the growth dynamics of the cell volume. The results of studies demonstrated that the pollen grain increases in size owing to the growth of the vegetative cell. The generative one does not grow. RNA synthesis and that of proteins in differentiating pollen cells has a different course. In the growing vegetative cell it lasts longer and is more intensive than in the generative cell which does not grow. RNA and protein synthesis in the vegetative cell take place in the period from the callose stage to the stage of lemon-shaped generative cell, that is in the period of phases G<sub>1</sub>, S and G<sub>2</sub>. This synthesis is positively correlated with the growth of the pollen grain. RNA and protein synthesis in the generative cell comprises the period from the callose-less lenticular stage to the stage of spherical generative cell, that is the phases S and early phase G<sub>2</sub>. These results suggest that in the vegetative cell RNA and protein synthesis is utilised above all to increase of its cell, instead in non growing generative cell protein synthese is probably limited mostly to a histones and enzymatic proteins serving for the DNA replication process.

scholarly journals Structure of the generative cell wall complex after freeze substitution in pollen tubes of Nicotiana and Impatiens

1987 ◽  
Vol 88 (3) ◽  
pp. 373-378
Author(s):  
M. CRESTI ◽  
S. A. LANCELLE ◽  
P. K. HEPLER
Keyword(s):  
Cell Wall ◽  
Plasma Membranes ◽  
Generative Cell ◽  
Pollen Grains ◽  
Freeze Substitution ◽  
Pollen Tubes ◽  
Wall Material ◽  
Cell Cytoplasm ◽  
Stage Of Development

The mature generative cell in pollen grains and pollen tubes is surrounded by a wall complex that includes two plasma membranes, one facing the generative cell cytoplasm and one facing the vegetative cell cytoplasm, and usually some intervening wall material. After conventional chemical fixation, the two plasma membranes are very uneven and often appear to be joined, giving the impression that numerous plasmodesmata connect the vegetative and generative cells. These areas alternate with swollen, distorted areas, which give the wall complex the appearance of being composed of a chain of vesicles. Utilizing rapid freeze fixation and freeze substitution, we have re-examined the ultrastructure of the generative cell wall complex from pollen tubes grown in vitro, and the differences are striking. The two plasma membranes are very smooth and closely appressed to a layer of wall material. Occasionally the wall complex contains swollen areas, or varicosities, and these may contain pockets of lightly stained material, but again the surrounding plasma membranes are tightly appressed to these areas. Plasmodesmata are not seen, but this does not eliminate the possibility that they may exist at an earlier stage of development.

Fine Structure Study of Pollen Development in Haemanthus katherinae Baker

1971 ◽  
Vol 8 (2) ◽  
pp. 289-301
Author(s):  
JEAN M. SANGER ◽  
W. T. JACKSON
Keyword(s):  
Fine Structure ◽  
Vegetative Cell ◽  
Daughter Nucleus ◽  
Generative Cell ◽  
Pollen Grains ◽  
Cell Plate ◽  
Structure Study ◽  
Pollen Grain ◽  
Pollen Wall ◽  
Fibrillar Material

When microspores of the African blood lily divide, they form pollen grains which consist of 2 cells of unequal size. This is accomplished when the microspore nucleus is displaced from the centre of the grain prior to division. The displacement is always towards the side of the grain opposite the furrow, and large vacuoles form in the cytoplasm between the furrow and the nucleus. During cell division the cell plate curves around one daughter nucleus and fuses with the pollen wall to enclose the generative cell. The cell-plate attachment always occurs with the wall that is opposite the furrow of the grain. Most of the microspore's organelles become incorporated in the larger vegetative cell, whereas the generative cell has few, if any, plastids and only a small number of other organelles. The wall around the generative cell is composed of finely fibrillar material enclosed within 2 unit membranes. The generative cell eventually becomes detached from the pollen wall, becomes spheroidal, and moves to a position near the centre of the pollen grain. At the same time, the large vacuoles disappear from the vegetative cell and the number of organelles increases substantially.

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