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  • 1
    Electronic Resource
    Electronic Resource
    External hyphal production of vesicular-arbuscular mycorrhizal fungi in pasture and tallgrass prairie communities (1995)
    Springer
    Oecologia 103 (1995), S. 17-23 
    Details
    ISSN: 1432-1939
    Keywords: Mycorrhiza ; External hyphae ; Root morphology ; Grasslands ; Soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract External hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi were quantified over a growing season in a reconstructed tallgrass prairie and an ungrazed cool-season pasture. In both sites, hyphal lengths increased throughout the growing season. Peak external hyphal lengths were 111 m cm−3 of soil in the prairie and 81 m cm−3 of soil in the pasture. These hyphal lengths calculate to external hyphal dry weights of 457 μg cm−3 and 339 μg cm−3 of soil for prairie and pasture communities, respectively. The relationships among external hyphal length, root characteristics, soil P and soil moisture were also determined. Measures of gross root morphology [e.g., specific root length (SRL) and root mass] have a strong association with external hyphal length. Over the course of the study, both grassland communities experienced a major drought event in late spring. During this period a reduction in SRL occurred in both the pasture and prairie without a measured reduction in external hyphal length. Recovery for both the pasture and prairie occurred not by increasing SRL, but rather by increasing external hyphal length. This study suggests that growth is coordinated between VAM hyphae and root morphology, which in turn, are constrained by plant community composition and soil nutrient and moisture conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328420
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  • 2
    Electronic Resource
    Electronic Resource
    Pollination of sevenPlectranthus spp. (Lamiaceae) in southern Natal, South Africa (1999)
    Springer
    Plant systematics and evolution 218 (1999), S. 99-112 
    Details
    ISSN: 1615-6110
    Keywords: Lamiaceae ; Plectranthus ; Nemestrinidae ; Stenobasipteron ; Prosoeca ; Acroceridae ; Psilodera ; Anthophoridae ; Amegilla ; Pollination ; long-tubed flowers ; long-proboscid flies ; Natal Group sandstone ; adaptive radiation ; speciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genusPlectranthus (Lamiaceae) shows remarkable radiation on the sandstones of southern Natal and northern Transkei in South Africa, where six endemic species occur. Two of these endemic species,P. hilliardiae andP. oribiensis, are included in this study, as well asP. reflexus, for which only limited data are available. The other species that were studied areP. ambiguus, P. ciliatus, P. ecklonii, P. madagascariensis andP. zuluensis. Four of these taxa,P. ambiguus, P. hilliardiae, P. reflexus andP. saccatus var.longitubus, have uniquely long corolla-tubes (20–30mm) and this is related to pollination by nemestrinid flies of the genusStenobasipteron that have proboscides of similar length. Other nemestrinid species of the genusProsoeca have shorter proboscides and pollinate two species ofPlectranthus with shorter corolla-tube lengths (6–15mm). Acrocerid flies, tabanid flies and anthophorid bees are also important visitors to these species. This study on the pollination of seven species of varying corolla-tube lengths shows a correlation between floral tube length and proboscis length of insect visitors, many of which are recorded for the first time as pollinators ofPlectranthus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01087038
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of explant type on proliferation of Carica papaya L. in vitro (1990)
    Springer
    Plant cell, tissue and organ culture 21 (1990), S. 39-44 
    Details
    ISSN: 1573-5044
    Keywords: papaw ; papaya ; Carica papaya ; shoot proliferation ; explant type
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three papaya explant types (entire plantlets, plantlets with apices removed, or roots removed) were cultured on media with and without 2 μM BAP and 0.5 μM NAA. Best growth of lateral shoots occurred in the presence of exogenous hormones, on plants with apex removed but roots intact. The presence of roots increased the number of lateral shoots formed, irrespective of the presence or absence of the apex. Root initiation on harvested lateral shoots was significantly reduced (P〈0.01) when shoot length was〈5 mm. Rooted shoots grew rapidly into apically dominant plantlets before subculture to multiplication medium. This procedure has produced a technique that could produce 10 000 microcuttings in vitro from one plantlet in a year, and should be free of genetic off-types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034489
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  • 4
    Electronic Resource
    Electronic Resource
    Prevalences of fungal pathogens and othernatural enemies of cereal aphids (Homoptera:Aphididae) in wheat under dryland and irrigatedconditions in South Africa (2000)
    Springer
    BioControl 45 (2000), S. 179-199 
    Details
    ISSN: 1573-8248
    Keywords: entomophthorales ; parasitoids ; Russian wheat aphid ; Diuraphis noxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Surveys were conducted in the summer andwinter rainfall wheat producing regions of SouthAfrica in a first attempt to investigate theidentity and impact of entomopathogenic fungi withinthe cereal aphid complex. Wheat produced underdryland and irrigated conditions was surveyed duringthe 1996 and 1997 seasons. Six cereal aphid specieswere recorded of which the Russian wheat aphid, Diuraphis noxia, was the most abundantunder dryland conditions in the summer rainfallregion as opposed to the oat aphid, Rhopalosiphum padi, in the winter rainfallregion. Rose grain aphid, Metopolophiumdirhodum, was most prevalent underirrigated conditions in the summer rainfall region.Five species of entomopathogenic fungi were recordedincluding four entomophthorales and the hyphomycete,Beauveria bassiana. TheEntomophthorales included Pandora neoaphidis, Conidiobolus obscurus, C.thromboides, and Entomophthoraplanchoniana. Pandora neoaphidis wasthe most important etiological agent recorded fromD. noxia, with up to 50% mycosis recordedunder dryland conditions in the Bethlehem summerrainfall region. Similarly, P. neoaphidis wasthe most prevalent species within populations ofM. dirhodum. under irrigated conditions in theBergville/Winterton summer rainfall region (up to77% mycosis). However, mycoses of R. padi didnot exceed 1.7% in samples from these areas,suggesting that R. padi may be lesssusceptible to P. neoaphidis than M.dirhodum. Epizootics in populations of D.noxia under dryland conditions in both the winterand summer rainfall regions indicated a high levelof susceptibility to P. neoaphidis.Occurrences of hymenopterous parasitoids andpredators in populations of D. noxia were low,although a parasitism level of 25% was recorded inone small sample of R. padi collected from anirrigated field in the summer rainfall region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009981718582
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