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  • 1
    Electronic Resource
    Electronic Resource
    THE MECHANISMS OF POLLINATION AND FERTILIZATION IN PLANTS (2002)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 18 (2002), S. 81-105 
    Details
    ISSN: 1081-0706
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract In flowering plants, pollen grains germinate to form pollen tubes that transport male gametes (sperm cells) to the egg cell in the embryo sac during sexual reproduction. Pollen tube biology is complex, presenting parallels with axon guidance and moving cell systems in animals. Pollen tube cells elongate on an active extracellular matrix in the style, ultimately guided by stylar and embryo sac signals. A well-documented recognition system occurs between pollen grains and the stigma in sporophytic self-incompatibility, where both receptor kinases in the stigma and their peptide ligands from pollen are now known. Complex mechanisms act to precisely target the sperm cells into the embryo sac. These events initiate double fertilization in which the two sperm cells from one pollen tube fuse to produce distinctly different products: one with the egg to produce the zygote and embryo and the other with the central cell to produce the endosperm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.cellbio.18.012502.083438
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructure of the sperm of Plumbago zeylanica (1984)
    Springer
    Planta 162 (1984), S. 385-391 
    Details
    ISSN: 1432-2048
    Keywords: Angiosperm reproduction ; Mitochondrion (in pollen) ; Plastid (in pollen) ; Plumbago ; Pollen ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pollen grains of Plumbago zeylanica L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and organelle content. The larger of the two sperm cells (Svn) is distinguished by the presence of a long (approx. 30 μm) projection, which wraps around and lies within embayments of the vegetative nucleus. This cell contains numerous mitochondria, up to two plastids and, infrequently, microbodies. It is characterized by a larger volume and surface area and contains a larger nucleus than the other sperm cell. The second sperm cell (Sua) is linked by plasmodesmata with the Svn, but is unassociated with the vegetative nucleus. It is smaller and lacks a cellular projection. The Sua contains relatively few mitochondria, but numerous (up to 46) plastids and more microbodies than the other sperm. The degree of dimorphism in their content of heritable cytoplasmic organelles must at fertilization result in nearly unidirectional transmission of sperm plastids into just one of the two female reproductive cells, and preferential transmission of sperm mitochondria into the other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393450
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  • 3
    Electronic Resource
    Electronic Resource
    Calcium distribution in fertile and sterile anthers of a photoperiod-sensitive genic male-sterile rice (1998)
    Springer
    Planta 204 (1998), S. 183-192 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Anther ; Calcium ; Male sterility ; Oryza (fertility) ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Potassium antimonate was used to locate Ca2+ in fertile and sterile anthers of a photoperiod-sensitive genic male-sterile rice (Oryza sativa L. japonica). During the development of fertile anthers, abundant calcium precipitates accumulated in the anther walls and on the surface of pollen grains and Ubish bodies at the late developmental stage of the microspore, but not in the cytoplasm of pollen grains. Following the accumulation of starch grains in pollen, calcium precipitates on pollen walls diminished and increased in parenchymatous cells of the connective tissue. In sterile anthers, calcium precipitates were abundant in the middle layer and endothecium, but not in the tapetum, as was found in fertile anthers. A special cell wall was observed between the tapetum and middle layer of sterile anthers that appeared to relate to distinctive calcium accumulation patterns and poor pollen wall formation in the loculi. The formation of different patterns of antimonate-induced calcium precipitates in the anthers of photoperiod-sensitive genic male-sterile rice indicates that anomalies in the distribution of calcium accumulation correlate with the failure of pollen development and pollen abortion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050245
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  • 4
    Electronic Resource
    Electronic Resource
    Calcium distribution in fertilized and unfertilized ovules and embryo sacs of Nicotiana tabacum L. (1997)
    Springer
    Planta 202 (1997), S. 93-105 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Antimonate precipitation ; Calcium ; Embryo sac ; Fertilization ; Nicotiana (fertilization) ; Synergid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Potassium antimonate was used to localize Ca2+ in tobacco ovules from 0 to 7 d after anthesis in pollinated and emasculated flowers. Antimonate binds “loosely bound” Ca2+ into calcium antimonate; less-soluble forms are unavailable and free calcium usually escapes. Ovules are immature at anthesis. Abundant calcium precipitates in nucellar cells surrounding the micropylar canal. A difference between calcium in the two synergids emerges at 1 d, which is enhanced in pollinated flowers. The future receptive synergid accumulates more precipitates in the nucleus, cytoplasm and cell walls. After fertilization, micropyle precipitates diminish, and the ovule is unreceptive to further tube entry. In emasculated flowers 6 d after anthesis, ovular precipitates essentially disappear; however, flowers pollinated at 4–5 d and collected 2 d later largely restore their prior concentration of precipitates. Ovular precipitates occur initially in the nucellus, then the embryo sac, and finally the synergid and micropylar filiform apparatus. Possibility, calcium is released from the embryo sac, although no structural evidence of exudate formation was observed. Calcium precipitates in the ovule correlate with the ability of the ovule to be fertilized, suggesting that successful pollen tube entry and later development may require calcium of the class precipitated by antimonate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050107
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  • 5
    Electronic Resource
    Electronic Resource
    Populations of plastids and mitochondria during male reproductive cell maturation in Nicotiana tabacum L.: A cytological basis for occasional biparental inheritance (1994)
    Springer
    Planta 193 (1994), S. 115-122 
    Details
    ISSN: 1432-2048
    Keywords: Autophagy ; Cytoplasmic inheritance ; Generative cell ; Nicotiana (reproductive cells) ; Plastid diminution ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dynamics of plastid and mitochondrial populations in male reproductive cells of tobacco (Nicotiana tabacum L.) were examined during development using serial ultrathin sections and transmission electron microscopy to reconstruct 58 generative cells and 31 sperm cells at selected stages of maturation from generative cell formation through gametic fusion. The first haploid mitosis resulted in incomplete exclusion of plastids providing an average of 2.81 plastids and 82.7 mitochondria for each newly formed generative cell. During generative-cell maturation, plastid content decreased to an average of 0.48 plastids/generative cell at anthesis owing to autophagy of organelles. Plastids were present in low frequency within generative and sperm cells in the pollen tube and appeared to be transmitted, according to observations immediately prior to fertilization. This forms a cytological basis for genetic reports of occasional biparental plastid inheritance. In contrast, mitochondria were transmitted in larger numbers, and approximately 80 mitochondria per generative cell or sperm cell pair were retained throughout development. This provides a potentially stable source for the transmission of male mitochondrial DNA, if present at fertilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191614
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitative cytology of the sperm cells of Brassica campestris and B. oleracea (1987)
    Springer
    Planta 170 (1987), S. 446-452 
    Details
    ISSN: 1432-2048
    Keywords: Brassica (sperm cell) ; Cytoplasmic inheritance ; Double fertilization ; Mitochondrion ; Pollen ; Vegetative nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pollen grains of Brassica campestris L. var. acephala DC and B. oleracea L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and mitochondrial content. The larger of the two sperm cells (Svn) is distinguished by the presence of a blunt evagination, which in B. oleracea wraps around and lies within shallow furrows on the vegetative nucleus and in B. campestris can penetrate through internal enclaves of the vegetative nucleus. This sperm cell contains more mitochondria in both species than the second sperm cell (Sua). This latter cell is linked to the first by a common cell junction with the S vn, but is not associated with the vegetative nucleus and lacks a cellular evagination. Such differences are indicative of a system of cytoplasmic heterospermy in which sperm cells possess significantly different quantities of mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402978
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  • 7
    Electronic Resource
    Electronic Resource
    Sperm cell surface characteristics of Plumbago zeylanica L. in relation to transport in the embryo sac (1999)
    Springer
    Planta 208 (1999), S. 539-544 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Fertilization ; Male germ unit ; Myosin Nitella ; Plumbago ; Sperm transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Myosin associated with the male germ cells of angiosperms interacts with actin, promoting transport of the non-motile generative and later sperm cells in the pollen tube. Myosin localizing on the sperm cell plasma membrane seems negligible in Plumbago, as reflected by the absence of: (i) anti-myosin labeling using immunoelectron microscopy, (ii) sperm motility on actin matrices, and (iii) electrophoretic movement changes after addition of antibody. Sperm cells injected directly into actively streaming Nitella internodal cells, however, follow actin bundles and their movement is sensitive to ATP and Mg2+. This may be based on simple charge binding since negatively charged latex beads also migrate on actin, whereas neutral or positively-charged latex beads do not. Sperm cells are negatively charged according to capillary microelectrophoresis, whereas killed sperm cells, which are positively charged do not migrate. The sperm cell that normally fertilizes the egg has a higher calculated charge (8.277 × 103 esu/cm2) compared with the sperm cell that fuses with the central cell (6.120 × 103 esu/cm2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050591
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  • 8
    Electronic Resource
    Electronic Resource
    Patterns of embryo-sac organization, synergid degeneration and cotyledon orientation in Linum usitatissimum L. (1990)
    Springer
    Planta 182 (1990), S. 52-57 
    Details
    ISSN: 1432-2048
    Keywords: Embryo sac ; Female germ unit ; Fertilization (angiosperms) ; Linum ; Megagametophyte (angiosperms) ; Synergid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The embryo sac of Linum usitatissimum consists, as in most angiosperms, of the egg, two synergids, central cell and antipodals. In Linum the embryo sac is strongly polarized in the longitudinal axis, but rotationally random relative to the vascular bundles of the ovule and ovary. Synergids designated right or left based on their orientation relative to the egg can be distinguished unambiguously if viewed from one pole of the embryo sac — in this case, the chalaza was used as the reference point. The synergid most likely to degenerate is the left (60%), proximal (52.3%) or septal-facing (52.7%) synergid. The volume and the surface area of the filiform apparatus of the left synergid is significantly smaller than that of the right synergid. Synergid-degeneration patterns varied between individual plants, indicating genetic control; however, the preference for the proximal and septal-facing synergid, although weak, indicates the possibility of some physiological influence. The cotyledons appear to assume bilateral symmetry with respect to the ovule only once endosperm digestion has begun. As the cotyledons grow, the embryo rotates to occupy the widest part of the embryo sac, thus imposing bilateral symmetry between the embryo and seed; prior to that time, the early and heart-shaped embryos are randomly oriented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239983
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  • 9
    Electronic Resource
    Electronic Resource
    Male reproductive cell development in Nicotiana tabacum: male germ unit associations and quantitative cytology during sperm maturation (1994)
    Springer
    Sexual plant reproduction 7 (1994), S. 324-332 
    Details
    ISSN: 1432-2145
    Keywords: Generative cell ; Male germ unit Nicotiana tabacum ; Pollen tube ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Generative and sperm cells were examined at four stages of development from generative cell formation to sperm cell maturation using serial transmission electron microscopy. The generative cell and vegetative nucleus are associated in a male germ unit association during pollen maturation and tube elongation, except for generative cell mitosis. At late stages of prophase, this association loosens; the generative cell separates from the vegetative nucleus at metaphase. Slender, unbranched, or occasionally branched projections may be found at one or both ends of the generative cell, or they may be single, blunt, and short. Slender projections are rare during anaphase and telophase. The vegetative nucleus moves back into apposition with one sperm cell at the end of mitosis. During the re-establishment of the association, the vegetative nucleus first touches the end of the leading sperm cell and then moves next to the middle of the sperm nucleus. As the sperm cells enter interphase, a conventional association is re-established between one cell and the vegetative nucleus through one or more long and slender cytoplasmic extensions; these associations are maintained throughout later passage in the pollen tube. During maturation, a significant increase occurs in the surface area of the sperm cells (particularly in the sperm cell in association with the vegetative nucleus), and a lesser increase in nuclear volume and surface area. Other sperm cell parameters, including those of heritable organelles, remain unchanged during sperm cell maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230511
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  • 10
    Electronic Resource
    Electronic Resource
    Transmission of male cytoplasm during fertilization in Nicotiana tabacum (1994)
    Springer
    Sexual plant reproduction 7 (1994), S. 313-323 
    Details
    ISSN: 1432-2145
    Keywords: Cytoplasmic inheritance Double fertilization ; Embryo sac Mitochondrial transmission ; Tobacco ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Serially sectioned embryo sacs of Nicotiana tabacum were examined during fertilization events using transmission electron microscopy. After pollen tube discharge, the outer membrane of the sperm pair is removed, the two sperm cells are deposited in the degenerate synergid and the sperm cells migrate to the chalazal edge of the synergid where gametic fusion occurs. During fertilization, the male cytoplasm, including heritable organelles, is transmitted into the female reproductive cells as shown by: (1) the cytoplasmic confluence of one sperm and the central cell during cellular fusion, (2) the occurrence of sperm mitochondria (distinguished by ultrastructural differences) in the zygote cytoplasm and adjacent to the sperm nucleus, (3) the presence of darkly stained aggregates which are found exclusively in mature sperm cells within the cytoplasm of both female cells soon after cell fusion, and (4) the absence of any large enucleated cytoplasmic bodies containing recognizable organelles outside the zygote or endosperm cells. The infrequent occurrence of plastids in the sperm and the transmission of sperm cytoplasm into the egg during double fertilization provide the cytological basis for occasional biparental plastid inheritance as reported previously in tobacco. Although sperm mitochondria are transmitted into the egg/zygote, their inheritance has not been detected genetically. In one abnormal embryo sac, a pair of sperm cells was released into the cytoplasm of the presumptive zygote. Although pollen tube discharge usually removes the inner pollen-tube plasma membrane containing the two sperm cells, this did not occur in this case. When sperm cells are deposited in a degenerating synergid or outside of a cell, this outer membrane is removed, as it apparently is for fertilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230510
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