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.

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.

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.

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.

Ultrastructural changes of Arabidopsis thaliana pollen during final maturation and rehydration

Zygote ◽  
1993 ◽  
Vol 1 (2) ◽  
pp. 173-179 ◽  
Author(s):  
A.C. Van Aelst ◽  
E.S. Pierson ◽  
J.L. Van Went ◽  
M. Cresti
Keyword(s):  
Arabidopsis Thaliana ◽  
Outer Part ◽  
Peripheral Region ◽  
Pollen Grain ◽  
Ultrastructural Changes ◽  
Sperm Cells ◽  
Lipid Bodies ◽  
Electron Dense Material ◽  
Final Maturation ◽  
The Individual

SummarySeveral ultrastructural changes occur during dehydration and subsequent rehydration of Arabidopsis thaliana pollen. The cytoplasmic channels, present in the outer part of the intine of the mature, dehydrating pollen grain, degenerate and develop into electron-dense inclusions. At the same time a large quantity of electron-dense material is deposited in the cavities of the exine. A large number of vesicles is produced in the vegetative cell, and they become predominantly located in the peripheral region near the intine. Starch of amyloplasts is consumed and the lipid bodies which originally surround the sperm cells become randomly distributed. In addition, the individual lipid bodies become enveloped by single rough endoplasmic reticulum cisterns.

scholarly journals Ultrastructural characterization of microlipophagy induced by the interaction of vacuoles and lipid bodies around generative and sperm cells in Arabidopsis pollen

PROTOPLASMA ◽  
2020 ◽  
Vol 258 (1) ◽  
pp. 129-138
Author(s):  
Kae Akita ◽  
Tomoko Takagi ◽  
Keiko Kobayashi ◽  
Kazuyuki Kuchitsu ◽  
Tsuneyoshi Kuroiwa ◽  
...  
Keyword(s):  
Generative Cell ◽  
Lipid Body ◽  
Sperm Cells ◽  
Lipid Bodies ◽  
Pollen Maturation ◽  
Ultrastructural Characterization ◽  
Pollen Stage ◽  
And Function ◽  
Arabidopsis Pollen

AbstractDuring pollen maturation, various organelles change their distribution and function during development as male gametophytes. We analyzed the behavior of lipid bodies and vacuoles involved in lipophagy in Arabidopsis pollen using serial section SEM and conventional TEM. At the bicellular pollen stage, lipid bodies in the vegetative cells lined up at the surface of the generative cell. Vacuoles then tightly attached, drew in, and degraded the lipid bodies and eventually occupied the space of the lipid bodies. Degradation of lipid began before transfer of the entire contents of the lipid body. At the tricellular stage, vacuoles instead of lipid bodies surrounded the sperm cells. The degradation of lipid bodies is morphologically considered microautophagy. The atg2-1 Arabidopsis mutant is deficient in one autophagy-related gene (ATG). In this mutant, the assembly of vacuoles around sperm cells was sparser than that in wild-type pollen. The deficiency of ATG2 likely prevents or slows lipid degradation, although it does not prevent contact between organelles. These results demonstrate the involvement of microlipophagy in the pollen development of Arabidopsis.

scholarly journals Ultrastructural Changes in the Pancreata of Selenium-Vitamin E-Deficient Chicks

1977 ◽  
Vol 14 (6) ◽  
pp. 629-642 ◽  
Author(s):  
A. H. Rebar ◽  
J. F. Van Vleet
Keyword(s):  
Endoplasmic Reticulum ◽  
Vitamin E ◽  
Acinar Cell ◽  
Interstitial Fibrosis ◽  
Ultrastructural Changes ◽  
Zymogen Granules ◽  
Cell Cytoplasm ◽  
Torula Yeast ◽  
Cell Changes ◽  
Ductular Proliferation

Three hundred and seventy 1-day-old male, white Leghorn chicks were divided into seven groups and fed a series of semipurified torula yeast diets either deficient in or supplemented with selenium and vitamin E. Chicks in each group were necropsied sequentially and the pancreata examined by light microscopy. Selected pancreata of selenium deficient chicks in various stages of the deficiency disease were examined by electron microscopy. Supplements of either selenium (0.2 mg/kg) or vitamin E (100 IU/kg diet) resulted in protection against pancreatic lesions. Changes in pancreata of selenium deficient chicks progressed from cytoplasmic vacuolation of acinar cell cytoplasm to focal disseminated acinar necrosis. There was ductular proliferation and interstitial fibrosis in advanced lesions. Acini around islets were less frequently affected than acini further away. Ultrastructurally, the mildest lesions were focal dilation of the endoplasmic reticulum and autophagic vacuoles in acinar cell cytoplasm. Necrotic areas contained both membranous and granular debris and fragments of intact endoplasmic reticulum. In fibrotic pancreata the main acinar cell changes were uniform dilation of endoplasmic reticulum and reduction in number of zymogen granules.

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.

An ultrastructural study of pollen development in tomato (Lycopersicon esculentum). I. Tetrad to early binucleate microspore stage

1993 ◽  
Vol 71 (8) ◽  
pp. 1039-1047 ◽  
Author(s):  
P. L. Polowick ◽  
V. K. Sawhney
Keyword(s):  
Endoplasmic Reticulum ◽  
Lycopersicon Esculentum ◽  
Ultrastructural Study ◽  
Pollen Development ◽  
Pollen Wall ◽  
Ultrastructural Changes ◽  
Dense Matrix ◽  
Tetrad Stage ◽  
Microspore Stage ◽  
Electron Dense Matrix

Microspores undergo considerable ultrastructural changes between the tetrad and early binucleate microspore stages of microsporogenesis in tomato (Lycopersicon esculentum). Pollen wall deposition began late in the tetrad stage, and by the early microspore stage a lamellar foot layer and tectum were deposited. Sculpturing of the tectum was evident by the early binucleate microspore stage. Dictyosomes and vesicles were abundant during the period of pollen wall formation. Plastids were associated with the endoplasmic reticulum (ER) to form plastid–ER complexes, from the late tetrad to the vacuolate microspore stage. At the vacuolate microspore stage, endoplasmic reticulum independent of plastids was also observed, and at the early binucleate microspore stage ER was not associated with plastids. Free ribosomes were evenly distributed throughout the cytoplasm until the vacuolate microspore stage when they were organized into polysomes. Mitochondria were spherical to ellipsoid, with an electron-dense matrix and swollen cristae, until the early binucleate microspore stage when they were highly elongate and became convoluted. Key words: Lycopersicon esculentum, microsporogenesis, pollen development, tetrads, tomato, ultrastructure.

Aspterric Acid and 6-Hydroxymellein, Inhibitors of Pollen Development in Arabidopsis thaliana, Produced by Aspergillus terreus

2002 ◽  
Vol 57 (5-6) ◽  
pp. 459-464 ◽  
Author(s):  
Atsumi Shimada ◽  
Miyako Kusano ◽  
Sumiyo Takeuchi ◽  
Shozo Fujioka ◽  
Tomohisa Inokuchi ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Microscopic Examination ◽  
Pollen Development ◽  
Aspergillus Terreus ◽  
Higher Plants ◽  
Molecular Investigation ◽  
Microspore Stage ◽  
Stage 1

Aspterric acid (1) and 6-hydroxymellein (2), inhibitors of pollen development in Arabidopsis thaliana, have been isolated fromthe fungus Aspergillus terreus. 1 and 2 inhibited the pollen development at concentrations of 38 and 52 μᴍ, respectively. The microscopic examination of pollen development suggested that the inhibition by the treatment with 1 caused at meiosis and the inhibition by the treatment with 2 caused at microspore stage. 1 and 2 could be useful agents for the molecular investigation of anther and pollen development in higher plants.

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