Fine Structure Study of Pollen Development in Haemanthus katherinae Baker

1971 ◽  
Vol 8 (2) ◽  
pp. 317-329
Author(s):  
JEAN M. SANGER ◽  
W. T. JACKSON
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Final Stage ◽  
Structure Study ◽  
Pollen Grain ◽  
Developmental Period ◽  
Vegetative Nucleus ◽  
Lipid Bodies ◽  
Starch Granules ◽  
Flat Cisternae

The newly formed vegetative cell of the pollen grain of the African blood lily has a spheroidal nucleus, few dictyosomes, and a small amount of endoplasmic reticulum. Plastids are smaller than those of the microspore and usually lack starch granules. Mitochondria and lipid bodies are more numerous than they were in the microspores, but their appearance is unchanged. As the pollen grain matures, the vegetative nucleus becomes irregular in shape. There is a dramatic increase in the number of dictyosomes, starch accumulates in the plastids, and a moderately well developed system of endoplasmic reticulum appears in the form of flat cisternae. In the developmental period immediately preceding anthesis, the vegetative nucleus becomes lobate and small nucleoli replace the large nucleoli present earlier. Plastids lose their starch, lipid bodies disappear, and the endoplasmic reticulum becomes vesicular in this final stage before germination.

Fine Structure Study of Pollen Development in Haemanthus katherinae Baker

1971 ◽  
Vol 8 (2) ◽  
pp. 303-315
Author(s):  
JEAN M. SANGER ◽  
W. T. JACKSON
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Pollen Development ◽  
Generative Cell ◽  
Structure Study ◽  
Pollen Grain ◽  
Pollen Wall ◽  
Spheroidal Shape ◽  
Oriented System

The newly formed generative cell of the pollen grain of the African blood lily is spheroidal after its detachment from the pollen wall. Plastids are almost always excluded from the generative cell, while dictyosomes, mitochondria, ribosomes, endoplasmic reticulum, and microtubules are present throughout development of the cell. During the time that the generative cell is spheroidal, microtubules are found scattered randomly throughout the cytoplasm. The cell subsequently elongates and concurrently an oriented system of microtubules appears along the wall of the cell. The microtubules are aligned with their long axes parallel to the long axis of the cell. This system of microtubules persists in the generative cell throughout its development. The microtubules can be destroyed by exposure to isopropyl N-phenylcarbamate or colchicine and as a result the generative cell reverts to a near spheroidal shape.

scholarly journals Elektronenmikroskopische Beobachtungen an der generativen Zelle von Oenothera hookeri Torr. et Gray

1963 ◽  
Vol 18 (7) ◽  
pp. 562-566 ◽  
Author(s):  
Lothar Diers
Keyword(s):  
Endoplasmic Reticulum ◽  
Inclusion Bodies ◽  
Generative Cell ◽  
Cytoplasmic Inclusion ◽  
Pollen Grain ◽  
Lipid Bodies ◽  
Lamellar System ◽  
Varying Thickness ◽  
Cytoplasmic Inclusion Bodies ◽  
Germinating Pollen

In the germinating pollen grain the generative cell shows the structure of a meristematic cell. It is separated from the cytoplasm of the vegetative cell by a clearly visible wall, on the average about 30 — 60 mµ thick. This wall appears to be formed by two darkly stained membranes including a lighter region of varying thickness. In the generative cell there are a big nucleus, plastids which show a scarcely developed lamellar system but no starch grains, mitochondria, dictyosomes. very probably lipid bodies and unidentified cytoplasmic inclusion bodies. The endoplasmic reticulum is continuous with the membranes of the nuclear encelope and extends through the cytoplasmic substance in which no vacuoles are recognizable.

Uredospore development in Puccinia graminis

1969 ◽  
Vol 47 (12) ◽  
pp. 2061-2064 ◽  
Author(s):  
M. A. Ehrlich ◽  
H. G. Ehrlich
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Wall Layer ◽  
Tangential Section ◽  
Puccinia Graminis ◽  
Lipid Bodies ◽  
External Wall ◽  
Additional Information ◽  
Spine Development

The present paper reports a number of electron microscope observations on the protoplasm and walls of developing spores which provide additional information on uredospore wall and spine development and on the fine structure of organelles, particularly of mitochondria and endoplasmic reticulum and of lipid bodies in developing spores. Micrographs of partially extracted uredospore walls and of chromium-shadowed extracted sections demonstrate the architecture of the wall as seen in cross and tangential section. Three distinct wall zones are clearly visible with the external wall layer forming the boundary of the germinal pore.

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.

Structure study of the chalcogens and chalcogenides by X-ray absorption fine structure

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Hiroyuki Ikemoto ◽  
Takafumi Miyanaga
Keyword(s):  
Fine Structure ◽  
Covalent Bond ◽  
Narrow Channel ◽  
Structure Study ◽  
Chain Structure ◽  
Covalent Bonds ◽  
X Ray ◽  
Absorption Fine ◽  
Amorphous States ◽  
X Ray Absorption

AbstractIn this review, we make a survey of the structure studies for the chalcogen elements and several chalcogenides in liquid, amorphous and nanosized state by using X-ray absorption fine structure (XAFS). The chalcogen elements have hierarchic structures; the chain structure constructed with the strong covalent bond as a primary structure, and the weaker interaction between chains as a secondary one. Existence of these two kinds of interactions induces exotic behaviors in the liquid, amorphous and nanosized state of the chalcogen and chalcogenides. XAFS is a powerful structure analysis technique for multi-element systems and the disordered materials, so it is suitable for the study of such as liquid, amorphous and nanosized mixtures. In section 2, the structures for the liquid state are discussed, which show the interesting semiconductor-metal transition depending on their temperatures and components. In section 3, the structure for the amorphous states are discussed. Especially, some of chalcogens and chalcogenides present the photostructural change, which is important industrial application. In section 4, the structures of nanosized state, nanoparticles and isolated chain confined into the narrow channel, are discussed. The studies of the nanoparticle and the isolated chain reveal the alternative role between the intrachain covalent bonds and the interchain interaction.

scholarly journals THE FINE STRUCTURE OF ASTROCYTES IN THE CEREBRAL CORTEX AND THEIR RESPONSE TO FOCAL INJURY PRODUCED BY HEAVY IONIZING PARTICLES

1965 ◽  
Vol 25 (2) ◽  
pp. 141-157 ◽  
Author(s):  
David S. Maxwell ◽  
Lawrence Kruger
Keyword(s):  
Cerebral Cortex ◽  
Fine Structure ◽  
Electron Microscope ◽  
Reactive Astrocytes ◽  
Lipid Bodies ◽  
Particle Irradiation ◽  
Fibrous Astrocytes ◽  
Primitive Forms ◽  
Focal Injury ◽  
Glycogen Particles

Normal and reactive astrocytes in the cerebral cortex of the rat have been studied with the electron microscope following focal alpha particle irradiation. The presence of glycogen and approximately 60-A fibrils identify astrocyte cytoplasm in formalin-perfused tissue. The glycogen particles facilitate the identification of small processes and subpial and perivascular end-feet. Both protoplasmic and fibrous astrocytes contain cytoplasmic fibrils and should be distinguished on the basis of the configuration of their processes and their distribution. Acutely reactive astrocytes are characterized by a marked increase in the number of glycogen granules and mitochondria from the first day after irradiation. These cells later hypertrophy and accumulate lipid bodies and increased numbers of cytoplasmic fibrils. The glial "scar" consists of a greatly expanded volume of astrocyte cytoplasm filled with fibrils and displays no signs of astrocyte death, reversion to primitive forms, or extensive multiplication.

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