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  • 1
    Electronic Resource
    Electronic Resource
    Recent progress on sperm characterization in flowering plants (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 80 (1990), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The organization, isolation and physiology of the angiosperm male gamete has recently emerged as an area of special interest. Detailed in vivo studies have revealed: (1) that the functional unit of male reproduction is a‘male germ unit,’composed of two sperm cells and a physically associated vegetative nucleus; (2) that the two sperm cells are often cytoplasmically dimorphic, and (3) that some sperm cells appear to undergo preferential fertilization, preferentially fusing with either the egg or the proendospermaric central cell. Male gamete isolation has provided enrichments of up to 107 cells ml–1, with sperm integrity and viability demonstrated by the flunrochromatic reaction and ATP levels. Although results from biochemical and hybridoma antibody characterization are still preliminary, they indicate that sperm cells possess polypeptide expression patterns that are different from those of surrounding cells. These findings suggest the existence of an independent developmental program in the angiosperm male gamete.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1990.tb05695.x
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  • 2
    Electronic Resource
    Electronic Resource
    Indirect effects of fish on macrophytes in Bays Mountain Lake: evidence for a littoral trophic cascade (1992)
    Springer
    Oecologia 89 (1992), S. 476-481 
    Details
    ISSN: 1432-1939
    Keywords: Indirect-effects ; Najas flexilis ; Potamogeton diversifolius ; Helisoma anceps ; Lepomis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We began this experiment to test specific hypotheses regarding direct and indirect effects of fish predation on the littoral macroinvertebrate community of Bays Mountain Lake, Tennessee. We used 24 m2 enclosures in which we manipulated the presence and absence of large redear sunfish (Lepomis microlophus〉150 mm SL), and small sunfish (L. macrochirus and L. microlophus 〈50 mm SL) over a 16-mo period. Here we report on effects of fish predation on gastropod grazers that appear to cascade to periphyton and macrophytes. Both large redear sunfish and small sunfish maintained low snail biomass, but snails in fish-free controls increased significantly during the first 2-mo of the experiment. By late summer of the first year of the experiment, the difference in biomass between enclosures with and without fish had increased dramatically (〉10×). Midway through the second summer of the experiment, we noted apparent differences in the abundance of periphyton between enclosures containing fish and those that did not. We also noted differences in the macrophyte distribution among enclosures. To document these responses, we estimated periphyton cover, biovolume and cell size frequencies as well as macrophyte distributions among enclosures at the end of the experiment. When fish were absent, periphyton percent cover was significantly reduced compared to when fish were present. Periphyton cell-size distributions in enclosures without fish were skewed toward small cells (only 12% were greater than 200 m3), which is consistent with intense snail grazing. The macrophyte Najas flexilis had more than 60 x higher biomass in the fish-free enclosures than in enclosures containing fish; Potamogeton diversifolius was found only in fish-free enclosures. These results suggest a chain of strong interactions (i.e. from fish to snails to periphyton to macrophytes) that may be important in lake littoral systems. This contrasts sharply with earlier predictions based on cascading trophic interactions that propose that fish predation on snails would enhance macrophyte biomass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317152
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative three-dimensional study on the position of the female gametophyte and its constituent cells as a prerequisite for corn (Zea mays) transformation (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 72-76 
    Details
    ISSN: 1432-2242
    Keywords: Biotechnology ; Embryo sac ; Microinjection ; Micromanipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The position of the embryo sac in the spikelet and of the embryo sac's constituent cells within the sporophytic tissues of Zea mays was localized by scanning electron microscopy, serial thick sectioning, and computer three-dimensional reconstruction. Within certain limits, the embryo sac is consistently oriented in the same position inside of the spikelet. This information is a prerequisite for successful microinjections into the in situ female cells of Zea mays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223789
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  • 4
    Electronic Resource
    Electronic Resource
    PCR detection of transcripts homologous to the self-incompatibility gene in anthers ofBrassica (1991)
    Springer
    Theoretical and applied genetics 82 (1991), S. 466-472 
    Details
    ISSN: 1432-2242
    Keywords: Brassica oleracea ; Self-incompatibility ; S-locus ; Polymerase chain reaction ; Anther
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The polymerase chain reaction (PCR) is particularly well suited for the detection of rare sequences. Taking advantage of the recent isolation of sequences associated with stigma self-incompatibility inBrassica oleracea, we used PCR amplifications with primers synthesized to the S6 cDNA sequence, to demonstrate the presence of mRNA homologous to stigmaS-locus gene (SLG) in anthers during early microsporogenesis. In addition, otherS-locus-related (SLR) sequences were shown to be transcribed in sexual as well as in vegetative tissues (roots, leaves), suggesting that the SLG family might be involved not only in pollen-stigma recognition, but more generally in various forms of plant cell signalling processes. This information corroborates the recent discovery of a cDNA-deduced protein kinase from maize roots, whose extracellular receptor displays high homology withBrassica S-locus-specific glycoproteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588600
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  • 5
    Electronic Resource
    Electronic Resource
    Identification of a 32-kDa anther marker protein for androgenic response in maize, Zea mays L. (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 843-850 
    Details
    ISSN: 1432-2242
    Keywords: Maize ; Marker protein ; Cold pretreatment ; Androgenesis ; Embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Variations in the whole anther protein pattern have been investigated in a highly androgenic maize hybrid during the inductive pretreatment for androgenesis. It was found that a 32-kDa protein (MAR32) is induced and accumulates in the anthers during cold pretreatment of the tassel. A positive correlation between the rate of embryo formation via anther culture and the level of this protein after 7 days of cold treatment was observed. In addition, the in vivo synthesis of this protein by cold-pretreated anthers was demonstrated. Different responsive and non-responsive genotypes were also evaluated, and the accumulation of MAR32-like protein was only observed in certain responsive genotypes. The results suggest that the protein MAR32 is a marker for a form of androgenic responsiveness in maize.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00212611
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  • 6
    Electronic Resource
    Electronic Resource
    Survival at 20° C and cryopreservation of isolated sperm cells from Zea mays pollen grains (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 212-216 
    Details
    ISSN: 1432-2145
    Keywords: Corn ; Isolated sperm cells ; Survival ; FCR test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The survival of isolated sperm cells from maize pollen grains at 20° C and their cryopreservation were studied by means of the fluorochromatic reaction (FCR) test. An osmotic pressure of 500 mOsmol, a pH of 7 adjusted with MOPS buffer, and the ten-fold dilution of Brewbacker and Kwack salts enabled isolated sperm cells to survive for a maximum of 35 h at 20° C. The addition of 3 mM of calcium chloride or 0.1 % glucose also slightly improved survival. The addition of 1% glutamine gave the best percentage of FCR-positive cells at 20 h. The addition of all of these substances in a unique medium provoked the formation of spermcell aggregates that were FCR positive. With respect to cryopreservaton, 70% of the isolated sperm cells remained FCR positive after freezing at -80° C and quick thawing at 37° C in the selected survival medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228651
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  • 7
    Electronic Resource
    Electronic Resource
    A model for studying pollination and pod development in Brassica napus: the culture of isolated flowers (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 52-56 
    Details
    ISSN: 1432-2145
    Keywords: In vitro culture ; Brassica napus ; Pollination ; Pod ; Seed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A technique for cultivating isolated flowers of Brassica napus has been developed. Flowers were harvested at anthesis, the surface of their peduncles was then sterilized and they were cultivated in a hormonefree medium. We used an MS medium supplemented with 3% sucrose as a source of organic carbon. From our experiments, it was concluded that no exogenous growth regulator is required to ensure normal growth and development in vitro. The flowers, and thereafter the pods, can be kept in culture until seed maturity. After 30 days, seed development resulted in three types of seeds: (1) normal, (2) milky and (3) aborted. The results show that the number of seeds per pod was not dependent on the order of flowers on the raceme (except the first 10 flowers and flowers above row 50). Our study supports the validity of this model as an easy tool for studying pollination and early seed development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227583
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of ovular receptivity on seed set and fruit development in cucumber (Cucumis sativus L.) (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 139-146 
    Details
    ISSN: 1432-2145
    Keywords: Cucumber ; Cucumis sativus L. ; Female receptivity ; Fruit set ; Seed set ; Ovule development ; Ovary growth ; Pollen-tube growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seed set and fruit development in cucumber (Cucumis sativus L.) were studied in relation to female flower receptivity from day — 2 before anthesis to day + 2 after anthesis. The female cucumber flower is protogynous. The pistil was receptive 2 days before anthesis. The iso-electric focusing (IEF) patterns of the stigma/style proteins, were identical from day -5 to day +2. In pollinated flowers in vivo germination and pollen-tube growth in the ovary were affected by pistil age from day -2 to day +2. In addition, differences in sectorial filling in full seeds were observed within the fruits. A negative correlation was observed between the frequency of fertilized ovules in the pedoncular part of the fruit and ovary length at the time of pollination. In the whole fruit, significant differences in the number of full seeds and fruit size at maturity were found, and these were observed to be correlated with the various stages of female flower maturation at pollination. The day -2 and day +2 stages yielded the smallest fruits with few full seeds compared to the day -1, day 0 and day +1 stages, which had the biggest fruits and a large number of full seeds. A strong positive correlation was found between total seed number (including full and empty seeds), fruit length and weight at maturity. All these results suggest that both seed set in the different parts of the fruit and fruit development are controlled by ovular receptivity rather than by stigma/style receptivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227659
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  • 9
    Electronic Resource
    Electronic Resource
    Pollen-pistil interactions in Populus: β-galactosidase activity associated with pollen-tube growth in the crosses P. nigra x P. nigra and P. nigra x P. alba (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 249-256 
    Details
    ISSN: 1432-2145
    Keywords: Incongruity ; Pollen-pistil interactions ; Populus ; Pollen-tube growth ; β-galactosidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to understand the nature of interspecific barriers in Populus, we have explored pollen/pistil interactions in intra- and interspecific crosses Populus nigra x P. nigra and P. nigra x P. alba. The kinetics of pollen-tube growth demonstrated that P. nigra and P. alba pollen tubes have distinct behavioral patterns inside P. nigra pistils. P. alba pollen tubes exhibit an unique S-shaped growth curve and an arrested growth site near the sylodium. P. nigra pollen tubes exhibit two growth phases, in the stigmatic tissues and in the ovarian cavity respectively. P. nigra and P. alba curves diverge 5 h after controlled pollination and could be related to a change in the physiology of the P. nigra pollen tube, which shifts from an autotrophic to a heterotrophic type of nutrition. Protein analysis of pollinated stigmatic extracts (0,6 and 20 h after pollination) revealed qualitative and quantitative differences that are related to the presence of either P. nigra or P. alba pollen tubes inside the stigmatic tissues. Increasing numbers of protein bands were detectable from 0 to 20 h after pollination only in intraspecific cross. Glycoproteins were detected, and the differences observed were dependent of the cross. β-Galactosidase activity was found in pollinated stigmas, but an increase in its activity (one isozyme of pHi 4.2) between 6 h and 20 h after pollination was detected only in the intraspecific cross. This enzyme could play a role in heterotrophic pollen-tube nitrition, and its activity could be the final result of a series of interactions started by the initial pollen-stigma dialog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231902
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  • 10
    Electronic Resource
    Electronic Resource
    Organization of the early post-fertilization megagametophyte ofPopulus deltoides (1990)
    Springer
    Protoplasma 155 (1990), S. 153-165 
    Details
    ISSN: 1615-6102
    Keywords: Cytoplasmic inheritance ; Female germ unit ; Fertilization ; Gametic fusion mechanisms ; Male gamete ; Populus ; Synergid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Gynoecia ofPopulus deltoides, 48 to 60 h after pollination, were examined using transmission electron microscopy. The mature megagametophyte contains two synergids, an egg cell, a central cell with two unfused polar nuclei and three antipodals. Pollen tube passage between cells in the styloid, on the placenta and through the micropyle does not induce degeneration of surrounding cells. Pollen tube entry into the megagametophyte occurs through the degenerated synergid immediately adjacent to the filiform apparatus. The tube grows the length of the filiform apparatus 20–30 μm into the synergid, and then discharges its contents-two sperm cells, the vegetative nucleus, and pollen tube cytoplasm. Sperm cells appear progressively hypertrophied during their passage in the pollen tube. In the degenerate synergid, the sperm nucleus is located at one end of the cell and the remaining cytoplasm is diffuse, containing a large vacuole. Following transmission of sperm nuclei into the egg and central cell, one male nucleus fuses with the egg and the other fuses with the micropylar polar nucleus. Enucleate cytoplasmic bodies of apparent sperm origin were observed within the degenerated synergid. The gametic fusion mechanism in this plant appears to involve: (1) eccentric positioning of the nucleus within the sperm cell, (2) separation of cytoplasmic and nuclear portions of the sperm cell, and (3) fusion of the nuclear portion with the egg cell. This represents a previously undescribed mechanism by which male cytoplasmic organelles are eliminated from sperm cells prior to fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322625
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