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  • Pollen competition  (2)
  • Submergence asphyxia  (1)
  • contaminant inventory  (1)
  • Springer  (4)
  • Geological Society of America (GSA)
  • Oxford University Press
  • 2005-2009
  • 2000-2004
  • 1995-1999  (4)
  • 1996  (4)
Collection
Keywords
Publisher
  • Springer  (4)
  • Geological Society of America (GSA)
  • Oxford University Press
Years
  • 2005-2009
  • 2000-2004
  • 1995-1999  (4)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Coring artifacts and contaminant inventories in lake sediment (1996)
    Springer
    Journal of paleolimnology 15 (1996), S. 99-106 
    Details
    ISSN: 1573-0417
    Keywords: lake sediments ; gravity core ; freeze core ; coring artifacts ; contaminant concentration ; contaminant inventory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sediments of Lake 382, Experimental Lakes Area, Canada, were sampled at six sites using a 5-cm Wildco KB core sampler (KB), a similar device incorporating a ball check valve (BC), and a 0.2 m by 1.2 m flat-faced aluminum freeze core sampler (FC). Cores were sectioned at 1-cm intervals to a depth of 15 cm. Contaminant (210Pb and 137Cs) concentrations (Bq g-1) were measured by gamma spectroscopy, and inventories (Bq cm-2) were calculated following standard methods. Sediments collected using FC, BC and KB had similar contaminant concentrations, however, cores collected by FC and BC had lower estimated inventories than KB cores. Differences between estimates appear to be caused by differences in the water content (WC) of core material. Laboratory studies confirm that FC sediments have higher WC than tube-cored sediment. We hypothesize that ice crystal formation increases the WC of freeze cores, resulting in lower contaminant inventories. Loss of surficial sediment caused by a ‘bow wave’ may have a similar effect on BC samples. We conclude that KB core gear is appropriate for sampling sediments to measure contaminant concentrations and inventories in recently deposited sediments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176992
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of pollen selection on progeny vigor in a Cucurbita pepo × C. texana hybrid (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 885-890 
    Details
    ISSN: 1432-2242
    Keywords: Key words  Microgametophyte selection ; Pollen selection ; Pollen competition ; Cucurbita texana ; Cucurbita pepo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   We examined the effects of pollen selection for rapid pollen-tube growth on progeny vigor. First, we crossed a wild gourd (Cucurbita texana) to a cultivated zucchini (Cucurbita pepo cv `Black Beauty') to produce an F1 and then an F2 generation. Half of the F1 seeds were produced by depositing small loads of C. texana pollen onto the stigmas of C. pepo. These small pollen loads were insufficient to produce a full complement of seeds and, consequently, both the fast- and the slow-growing pollen tubes were permitted to achieve fertilization. An F2 generation was then produced by depositing small loads of F1 pollen onto stigmas of F1 plants. The F2 seeds resulting from two generations of small pollen loads are termed 'the non-selected line' because there was little or no selection for pollen-tube growth rate on these plants. The other half of the F1 and F2 seeds were produced by depositing large pollen loads (〉10000 pollen grains) onto stigmas and then allowing only the first 1% or so of the pollen tubes that entered the ovary to fertilize the ovules. We did this by excising the styles at the ovary at 12–15 h after pollination. The resulting F2 seeds are termed `the selected line' because they were produced by two generations of selection for only the fastest growing pollen tubes. Small pollen loads from the F2 plants, both the selected and the non-selected lines, were then deposited onto stigmas of different C. pepo flowers, and the vigor of the resulting seeds was compared under greenhouse and field conditions. The results showed that the seeds fertilized by pollen from the selected line had greater vegetative vigor as seedlings and greater flower and fruit production as mature plants than the seeds fertilized by pollen from the non-selected line. This study demonstrates that selection for fast pollen-tube growth (selection on the microgametophyte) leads to a correlated increase in sporophyte (progeny) vigor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050207
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of pollen selection on progeny vigor in a Cucurbita pepo x C. texana hybrid (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 885-890 
    Details
    ISSN: 1432-2242
    Keywords: Microgametophyte selection ; Pollen selection ; Pollen competition ; Cucurbita texana ; Cucurbita pepo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the effects of pollen selection for rapid pollen-tube growth on progeny vigor. First, we crossed a wild gourd (Cucurbita texana) to a cultivated zucchini (Cucurbita pepo cv ‘Black Beauty’) to produce an F1 and then an F2 generation. Half of the F1 seeds were produced by depositing small loads of C. texana pollen onto the stigmas of C. pepo. These small pollen loads were insufficient to produce a full complement of seeds and, consequently, both the fast- and the slow-growing pollen tubes were permitted to achieve fertilization. An F2 generation was then produced by depositing small loads of F1 pollen onto stigmas of F1 plants. The F2 seeds resulting from two generations of small pollen loads are termed the non-selected line because there was little or no selection for pollen-tube growth rate on these plants. The other half of the F1 and F2 seeds were produced by depositing large pollen loads (〉10 000 pollen grains) onto stigmas and then allowing only the first 1% or so of the pollen tubes that entered the ovary to fertilize the ovules. We did this by excising the styles at the ovary at 12–15 h after pollination. The resulting F2 seeds are termed ‘the selected line’ because they were produced by two generations of selection for only the fastest growing pollen tubes. Small pollen loads from the F2plants, both the selected and the non-selected lines, were then deposited onto stigmas of different C. pepo flowers, and the vigor of the resulting seeds was compared under greenhouse and field conditions. The results showed that the seeds fertilized by pollen from the selected line had greater vegetative vigor as seedlings and greater flower and fruit production as mature plants than the seeds fertilized by pollen from the non-selected line. This study demonstrates that selection for fast pollen-tube growth (selection on the microgametophyte) leads to a correlated increase in sporophyte (progeny) vigor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221902
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  • 4
    Electronic Resource
    Electronic Resource
    Physiological mechanisms for underwater endurance: Canada goose (Branta canadensis) versus Pekin duck (Anas platyrhynchos) (1996)
    Springer
    Journal of comparative physiology 166 (1996), S. 46-54 
    Details
    ISSN: 1432-136X
    Keywords: Cardiovascular system ; Chemosensitivity ; Oxygen stores ; Submergence asphyxia ; Aquatic birds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Maximum submergence time of Canada geese was 18% of that of similarly sized Pekin ducks. Due to a smaller respiratory system volume the oxygen store of Canada geese was 82% of that of Pekin ducks, accounting for approximately 33% of the difference in underwater survival times. The respiratory properties and volume of the blood were similar in both species. Both species utilised approximately 79% of the respiratory oxygen store and 90% of the blood oxygen store. Therefore, most of the species difference in survival times was due to a less effective oxygen-conserving cardiovascular response (bradycardia, peripheral vasoconstriction) in Canada geese. Duck cardiac chronotropic sensitivity to hypoxia during submergence was twice that observed in geese. Furthermore, a lower hypoxic ventilatory response was observed in geese than in ducks. Density of monoamine varicosities in hindlimb artery walls was lower in geese than ducks. However, electrical stimulation of the hindlimb muscles did not cause ascending vasodilation during submergence in either species, perhaps due to higher levels of catecholamines in submerged geese. We conclude that the major difference between species is higher oxygen chemosensitivity in ducks which effects a much more rapid and efficacious oxygen-conserving response during forced submergence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264638
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