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  • Articles  (194)
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Journal
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 480-485 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A reflectance anisotropy spectroscopy (RAS) and low-energy electron diffraction study of the InP(001) surface is presented. The surface was prepared by thermal desorption of an As-P capped epilayer grown by molecular beam epitaxy. RA spectra have been monitored over a spectral range of 1.5–5.5 eV at regular intervals during thermal decapping and annealing up to the point of decomposition (553–973 K). Each of the RA spectra of the surface reconstructions comprise positive (at 2.9 eV) and negative (at 1.8 eV) anisotropies which have been previously associated with P- and In-related bonding, respectively. Unlike other III-V (001) semiconductor surfaces, the evolution of different reconstructions cannot be explained in terms of a change in surface stoichiometry which involves loss of the anion species. In the case of InP(001) the P species contributes to the clean surface reconstruction from the early stages of decapping to the point of decomposition. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 79 (1957), S. 2146-2148 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 79 (1957), S. 2148-2150 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 1 (1879), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 10 (1976), S. 964-964 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Environmental Economics and Management 23 (1992), S. 289-300 
    ISSN: 0095-0696
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Economics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 12 (2000), S. 203-208 
    ISSN: 1432-2145
    Keywords: Key words Tristyly ; Trimorphic incompatibility ; Pollen trimorphism ; Partial incompatibility ; Clonal aquatic plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Eichhornia azurea (Pontederiaceae) is a mat-forming, clonal aquatic that inhabits lakes, marshes and river systems in many parts of the Neotropics. The species is tristylous with long-, mid-, and short-styled morphs commonly represented in natural populations. To investigate whether E. azurea possesses a trimorphic incompatibility system typical of tristylous species, we conducted a controlled pollination experiment on 15 clones representing the three style morphs from a natural population near Rosario, Argentina. Comparisons of fruit and seed set following self-, illegitimate, and legitimate pollinations clearly demonstrated the presence of trimorphic incompatibility in E. azurea. Self- and illegitimate pollinations produced significantly less fruit and seed than legitimate pollinations in all three style morphs. Pollen from the two anther levels within a flower exhibited contrasting compatibility relations in self-pollinations. In common with several other tristylous species in Pontederiaceae, the expression of self-incompatibility was weakest in the mid-styled morph and strongest in the short-styled morph. We discuss the ecological and evolutionary significance of the partial expression of trimorphic incompatibility in E. azurea.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 7 (1994), S. 273-281 
    ISSN: 1432-2145
    Keywords: Pollen-pistil interference ; Prior self-pollination ; Tristyly ; Self-incompatibility Stylar senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential inhibitory effects of incompatible pollen on outcrossed seed set were investigated in mass-flowering, self-incompatible, tristylous Pontederia sagittata. Prior application of self pollen, followed after 2, 4, or 6 h by compatible pollen, was conducted on five genotypes of each of the three style morphs under uniform glasshouse conditions. The greatest reductions in seed set occurred in pollinations of the long-styled (L) morph at the 6 h time interval. Smaller reductions were also found for this treatment in the mid-styled (M) morph. No significant reductions in seed set were observed in the short-styled (S) morph or in the other morphs at shorter time intervals. Observations of pollen germination and pollen tube growth indicated that the lack of inhibitory effects in the S morph may occur because relatively few pollen grains adhered to stigmas in selfpollinations. In the L and M morphs, early germination of self pollen may cause physical clogging of the stigma and style, resulting in a reduced number of compatible pollen tubes in styles. Observations of the structural integrity of styles indicated that prior germination of self pollen resulted in more rapid onset of pistil senescence, particularly in the L morph. These influences may contribute to the morph-specific differences in seed set observed following prior self-pollination of outcrossed flowers. The negative effects of incompatible pollen are likely to be most evident where ecological factors cause delays in the delivery of outcross pollen to stigmas.
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  • 9
    ISSN: 1432-1939
    Keywords: Key words Fruit and seed set ; Narcissus assoanus ; Pollen limitation ; Reproductive ecology ; Seed:ovule ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A recent literature review indicates that pollen limitation of female fertility is a common feature of flowering plants. Despite the ecological and evolutionary significance of pollen limitation, most studies have only examined fertility in a single population at one time. Here we investigate pollen limitation of fruit and seed set in five populations of Narcissus assoanus, a self- sterile, insect-pollinated geophyte, over 2–3 years in southern France. In common with many early spring flowering plants, pollinator visitation to N. assoanus is often infrequent. Supplemental hand-pollination of flowers with outcross pollen significantly increased overall fruit and seed set by 11% and 19%, respectively. Four of the five populations experienced some pollen limitation during the study. For a given year, there was significant variation in pollen limitation among populations. Two of the populations were pollen limited in one year but not in other years in which they were studied. Seed:ovule ratios for open- and hand-pollinated flowers averaged 0.29 and 0.33, respectively. While hand pollination significantly increased the seed:ovule ratio, the low value obtained indicates that the majority of ovules in flowers do not mature seeds despite hand pollination. The role of genetic and environmental factors governing low seed:ovule ratios in N. assoanus is discussed.
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  • 10
    ISSN: 1432-1939
    Keywords: Pontederia cordata ; Bombus ; Tristyly ; Pollination ; Behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences in the production and size of pollen grains produced by the three anther levels results in the morphs offering variable amounts of resources to pollen-collecting insects. Bumblebees (Bombus spp.) and the solitary bee Melissodes apicata used P. cordata primarily as a nectar source and therefore did not seem to exhibit any morph preference. In contrast, honeybees visited flowers mainly for pollen and preferred to forage on long-level anthers of the short-and mid-styled morphs. An analysis of the composition of corbicular pollen loads indicated that, relative to the frequency of production in the population: 1) honeybees collected an excess of pollen from long-level anthers; 2) bumblebees collected the three types of pollen without any apparent preference; and 3) M. apicata preferentially collected pollen from the short-level anthers — presumably because their proboscides are modified by the presence of tiny hairs. The results suggest that P. cordata in Ontario is serviced by a diverse, unspecialized pollinator fauna which is not co-adapted to the tristylous floral polymorphism.
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