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  • Avena sativa  (1)
  • Evolution  (1)
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  • 1
    ISSN: 1432-2242
    Keywords: Endosperm development ; Evolution ; Imprinting ; Incompatibility ; Reciprocal crosses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Endosperm Balance Number (EBN) and the polar-nuclei activation (PNA) hypotheses have been developed to interpret, explain and predict interspecific and interploidy crossabilities in the Solanums and the Gramineae, respectively. Although these two hypotheses evolved independently, they share a number of common features. Assignment of EBNs and ‘activation/response values’ (AVs/RVs) depend on plumpness, size, and germinability of hybrid seeds. Also, both hypotheses emphasize the importance of a balanced parental genic contribution for the normal development of endosperm. However, in the EBN hypothesis a 2 maternal∶1 paternal EBN ratio is a prerequisite for successful interspecific crossability, while the PNA hypothesis is based on the stimulative strength of the male nuclei to initiate mitotic divisions in the primary endosperm nucleus and is idependent on a 2∶1 ratio between the RV of the polar nuclei and the AV of the male gamete. Differences and similarities betweeen the EBN and PNA hypotheses are summarized and contrasted. It is proposed that EBN and PNA be considered as the same concept.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 83 (1995), S. 103-108 
    ISSN: 1573-5060
    Keywords: oat ; Avena sativa ; pollen grain size ; chromosome number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pollen grain size in many genera positively correlated with chromosome number. In this study, oat (Avena) pollen grain size was examined in diploids (2×=14, one species, for accessions), tetraploids (4×=28, five species, 20 accessions), hexaploids (6×=42, one species, eight cultivars), and in 10 octoploid (8×=56) accessions. Mature anthers ready to dehisce pollen were sampled from one to six plants per accession, and pollen grains were squeezed out of the anther with tweezers. Oat pollen grains are slightly elliptical, and the length of the major axis was found to be highly correlated with the minor axis width (r=0.94**). Pollen grain length, 39.3 μm for diploids, 41.3 μm for tetraploids, 47.0 μm for hexaploids, and 48.8 μm for octoploids, was positively correlated (r=0.86**) with ploidy level. No genomic or species effects appeared to influence this trait. Only tetraploidAvena vaviloviana accession PI 412767 produced two distinct class sizes of pollen grains, 99% normal (43.0 μm) and 1% large (52.7 μm).
    Type of Medium: Electronic Resource
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