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  • 1
    Electronic Resource
    Electronic Resource
    Histochemical studies of pollen: storage pockets in the endoplasmic reticulum (ER) (1968)
    Springer
    Histochemistry and cell biology 13 (1968), S. 169-182 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pollen grain of cotton (Gossypium hirsutum) was examined histochemically at the light and electron microscope level. The cytoplasm of the pollen contains an unusual storage unit which consists of a pocket of endoplasmic reticulum (ER) containing lipid droplets and dictyosome vesicles. The ER pockets are large enough to be seen with the light microscope if thin enough sections are used (0.3–1.5μ). The results of the histochemical analyses show that the dictysome vesicles are rich in carbohydrate and contain protein and lipid as well. The ER contains large amounts of protein which may be arginine rich. Some carbohydrates may also be present in the ER. The ER is covered with ribosomes so that the pockets are unusually rich storage units containing abundant protein, carbohydrate, lipid and RNA. The light microscope localization of carbohydrates was confirmed by the periodic acid-silver method. Other storage units in the cytoplasm were also studied. A new method for the embedding of plant tissue for thin sectioning for light microscopy is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266578
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  • 2
    Electronic Resource
    Electronic Resource
    Nuclear and cytoplasmic DNA synthesis in cotton embryos: a correlated light and electron microscope autoradiographic study (1972)
    Springer
    Histochemistry and cell biology 32 (1972), S. 1-22 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary To investigate the possibility, implied by an earlier report, that large amounts of degradable DNA are probably present in the cytoplasm of young cotton embryos, an investigation was undertaken to establish the distribution, amount and metabolic stability of DNA in cotton embryos. Several sensitive cytochemical tests failed to detect any but small amounts of extranuclear DNA. Quantitative determination of the nucleic acid content of embryos during embryogenesis showed that the amounts of DNA and RNA remained fairly constant during embryogenesis, with a ratio of RNA to DNA of about 3.5 to 1. Quantitative autoradiography at both the light and electron microscope levels of sections from embryos pulse-labeled with 3H-thymidine showed that the grain density over the nucleus and cytoplasm did not change during a seven-hour period after labeling, nor did the distribution of label in the cytoplasm. Virtually all incorporation was eliminated by the inclusion of iododeoxy-uridine in the medium. Almost all of the nuclear label and at least 90% of the cytoplasmic label after 3H-thymidine incorporation was eliminated by deoxyribonuclease. It was concluded that there are no unusual features related to DNA distribution or metabolism in cotton embryo; i.e., that only small amounts of DNA are present in the cytoplasm and that all of the DNA is metabolically stable. Approximately 40% of the cytoplasmic grains after 3H-thymidine labeling were not associated with either plastids or mitochondria (i.e., were more than 0.1 micron distant). No fully satisfactory explanation for such an apparently high figure could be given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277467
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  • 3
    Electronic Resource
    Electronic Resource
    Pattern of DNA synthesis in the meristematic cells of sinapis (1966)
    Springer
    Histochemistry and cell biology 6 (1966), S. 85-92 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary High-resolution autoradiographs were made of ultrathin sections in the shoot apex and the very young leaves of Sinapis alba fed with tritiated thymidine for 4 hours. Three types of labeled nuclei were found. (1) Those labeled in both the dispersed and the condensed chromatin, (2) those labeled only in the dispersed chromatin, and (3) those labeled only in the condensed chromatin. A distinct cytoplasmic labeling was found. Proplastids and mitochondria were the only significantly labeled entities in the cytoplasm. DNA synthesis in these organelles seems to be synchronized with DNA synthesis in the nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277968
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  • 4
    Electronic Resource
    Electronic Resource
    Cotton embryogenesis: The identification, as nuclei, of the X-bodies in the degenerated synergid (1968)
    Springer
    Planta 84 (1968), S. 122-133 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The “x-bodies” present in the degenerated synergid of cotton were shown to contain DNA by specific staining with Azure B, the Feulgen procedure, and by labelling with 3H-actinomycin D. They are identified on a morphological basis as the degenerated vegetative nucleus of the pollen tube which is always found in the degenerated synergid tip, and as the degenerated synergid nucleus, which is found about halfway up the degenerated synergid near the side towards the central cell. The positions of these nuclei and of some other structures have been used to construct a tentative description of some of the events occurring during pollen-tube discharge and movement of the sperm through the synergid. Some observations which may indicate some of the factors involved in interaction of the synergid and pollen tube cytoplasm are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398390
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  • 5
    Electronic Resource
    Electronic Resource
    Double fertilization: a personal view (1998)
    Springer
    Sexual plant reproduction 11 (1998), S. 1-5 
    Details
    ISSN: 1432-2145
    Keywords: Key words Advances in microscopy ; Double fertilization ; Guignard-Nawaschin ; Personal account
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This year marks the 100th anniversary of the discovery of double fertilization by Nawaschin in St. Petersburg, Russia and, independently, Guignard in France. This discovery came at the end of a period of controversy about fertilization in angiosperms and ushered in a new period of intense research. Still, by 1950, there were many unanswered questions about double fertilization because of limitations of the light microscope. The introduction of the electron microscope stimulated new research and helped resolve some of the questions. My own research with the electron microscope and that of people who worked in my laboratory is recounted and some of the still unanswered questions raised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050113
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  • 6
    Electronic Resource
    Electronic Resource
    An electron microscope study on in vitro parthenogenesis in sunflower (1989)
    Springer
    Sexual plant reproduction 2 (1989), S. 154-166 
    Details
    ISSN: 1432-2145
    Keywords: Helianthus annuus ; Unfertilized ovule culture ; Parthenogenesis ; Ultrastructure ; Proembryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electron microscope studies have been conducted on the parthenogenesis induced by in vitro culture of unfertilized ovules of sunflower (Helianthus annuus). In comparison with the state of the egg prior to inoculation, some eggs 5 days after culture show striking ultrastructural changes, which include, among others, nuclear migration, an increase in the number and activity of the organelles, a loss of polarity and wall formation at the chalazal end of the cell. Most of these changes are similar to those that occur normally in the zygote, indicating that parthenogenic development has been triggered in these eggs. Such eggs have been termed activated and are presumed to be capable of undergoing parthenogenesis. The parthenogenic proembryos which result share some features in common with zygotic proembryos. In addition, some parthenogenic proembryos exhibit unique properties not found in zygotic proembryos. These include embryos that consist of two parts differing markedly in density, an inversion of polarity, the frequent occurrence of autophagic vacuoles, the thickening of cell walls, a centripetal growth mode of wall formation, the appearance of an incomplete cell wall, free nuclear division, amitosis and degeneration. We believe that these ultrastructural peculiarities are the effects of in vitro culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192762
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  • 7
    Electronic Resource
    Electronic Resource
    Studies of pollen maturation in cotton: the storage reserve accumulation phase (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 117-127 
    Details
    ISSN: 1432-2145
    Keywords: Pollen maturation ; Gossypium hirsutum L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study follows the maturation of the pollen grain of cotton (Gossypium hirsutum L.), particularly the development of the vegetative cytoplasm and the various storage products formed. CTEM, HVEM, stereoscopy, and cyto-histochemistry were used to examine the events occurring during the 9 days before anthesis. Starch began to accumulate in plastids at anthesis minus 9 days and reached a peak concentration shortly before anthesis; lipid deposition followed a similar pattern, but started at 6 days before anthesis. Lipid bodies were always seen closely oppressed to the endoplasmic reticulum (ER). Dictyosomes appear active during the entire 9 days; first producing vesicles involved in the formation of the intine and, later, producing vesicles stored in the pollen grain. The dictyosome vesicles appear to contain polysaccharides and concentrate in layers around the lipid bodies. Ribosomes increase in number from 6 days before anthesis and are particularly numerous in the mature pollen. From anthesis minus 6 days until anthesis, the ER cisternae become increasingly inflated and, in the hours immediately before pollen release, form pockets filled with lipid bodies and dictysosome vesicles. The mature pollen has a core region filled with ER pockets and a peripheral cytoplasm in which such pockets are generally lacking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194870
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 166-175 
    Details
    ISSN: 1432-2145
    Keywords: Helianthus annuus ; Ultrastructure ; Micropyle ; Pollen tube ; Synergid degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190000
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  • 9
    Electronic Resource
    Electronic Resource
    An ultrastructural study of early endosperm development and synergid changes in unfertilized cotton ovules (1977)
    Springer
    Planta 133 (1977), S. 179-189 
    Details
    ISSN: 1432-2048
    Keywords: Embryo sac ; Endosperm ; Fertilization ; Gossypium ; Synergids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Excised, unfertilized cotton (Gossypium hirsutum L.) ovules were cultured for 1–5 days postanthesis and embryo-sac development was studied with the electron microscope. In some ovules the two polar nuclei fuse and the diploid endosperm nucleus goes through a limited number of free nuclear divisions after 2–3 days in culture. Each nucleus has two nucleoli, in contrast to nuclei of fertilized triploid endosperm which have three nucleoli. Precocious cell walls form between the endosperm nuclei on the 3rd day in culture. The morphology of the plastids, mitochondria, rough endoplasmic reticulum (RER), dictyosomes and microbodies, and the amount of starch and lipid in the diploid cellular endosperm are similar to those of the central cell. A few large helical polysomes appear close to plastids and mitochondria. After 2 days in culture, one of the two synergids in the unfertilized cultured ovules shows degenerative changes which in fertilized ovules are associated with the presence of the pollen tube, i.e., increase in electron density, collapse of vacuoles, irregular darkening and thickening of mitochondrial and plastid membranes, disappearance of the plasmalemma and the membranes of the plasmalemma and the membranes of the RER. The second synergid remains unchanged in appearance. The egg cell does not shrink or divide or show structural changes characteristic of the cotton zygote. Embryo-sac development is arrested on the 4th and 5th days in culture. The nucellus continues growth and at 14 days crushes the degenerate embryo sac.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391917
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  • 10
    Electronic Resource
    Electronic Resource
    Cotton embryogenesis: The zygote (1968)
    Springer
    Planta 79 (1968), S. 346-366 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The zygote of cotton (Gossypium hirsutum) remains undivided for approximately $$2{\mathbf{\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} }}$$ days following fertilization. The changes which occur during this period can be divided into two stages. During stage 1 the zygote decreases in volume so that its volume becomes one half that of the egg. Correlated with this change a number of alterations occur in the endoplasmic reticulum (ER) numerous enlargements form; it becomes closely associated with the plasma membrane; and an internal network of tubes appears in it. The plastids and mitochondria become grouped around the zygote nucleus. The ribosomes form large, helical polysomes which are arranged as shells around the plastids and mitochondria. Starch accumulation and wall formation over the chalazal end of the cell, which begins during the end of stage 1, continues during stage 2. A new set of ribosomes appear in the cytoplasm. These either remain single, or aggregate into small polysomes. The large, helical polysomes of stage 1 persist. Ultimately the zygote becomes a highly polarized cell, rich in starch, surrounded by a wall, filled with a tube containing ER, and two types of polysomes, one composed of ribosomes present in the egg and the other of ribosomes produced by the zygote nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386917
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