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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological invasions 2 (2000), S. 123-140 
    ISSN: 1573-1464
    Keywords: African grasses ; ecophysiology ; ecosystem effects ; global change ; invasions ; pasture conversion ; tropical America
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clearing of natural vegetation for pastures and the deliberate introduction of African grasses constitute significant threats to the biological diversity of the tropics, subtropics, and warm temperate regions of the Americas. African grasses have escaped from cultivated pastures and revegetated rangeland sites and invaded natural areas at alarming rates. Invaded ecosystems tend to be biotically impoverished and differ markedly from adjacent non-invaded areas in structure and function. Effects of pasture creation and invasion by African grasses on ecosystem processes (transformation and flux of energy and matter) are primarily related to loss of woody species and changes in the fire regime. However, the ecophysiological attributes of the African grasses (e.g. high biomass allocation to leaves, high growth rate, and high leaf-level gas exchange rates) also have important consequences. Here we describe the extent of pasture creation with African grasses and their invasive spread in the New World and review ecological effects of these land-cover changes. We highlight a number of comparative ecophysiological studies within the context of mechanisms responsible for invasion by African grasses and resulting ecosystem change.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5028
    Keywords: abscission ; ethylene ; ETR1 ; geranium ; receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated two cDNAs from geranium, PhETR1 and PhETR2. The deduced amino acid sequences of PhETR1 and PhETR2 share 78% and 79% identity with ETR1 from Arabidopsis thaliana respectively. These genes are members of a multigene family and are expressed at moderate levels in leaves, pedicels, sepals, pistils and petals, and at very low levels in roots. PhETR1 and PhETR2 mRNAs are expressed in geranium florets long before they are receptive to pollination and transcript levels remain constant throughout floral development. Message levels of PhETR1 and PhETR2 in pistils and receptacles are unaffected by self-pollination or treatment with 1 μ/l ethylene that induces petal abscission. Our results indicate that the amount of PhETR1 and PHETR2 mRNA is not indicative of the level of sensitivity of geranium florets to ethylene.
    Type of Medium: Electronic Resource
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