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  • 1
    Electronic Resource
    Electronic Resource
    Terpenoids of the essential oil from Molopospermum peloponnesiacum roots
    Amsterdam : Elsevier
    Phytochemistry 20 (1981), S. 828-830 
    Details
    ISSN: 0031-9422
    Keywords: Apiaceae ; Molopospermum peloponnesiacum ; essential oil constituents ; gas chromatographs ; spectroscopy.
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0031-9422(81)85188-6
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  • 2
    Electronic Resource
    Electronic Resource
    Occurrence of 1,5-dimethylcyclodeca-1,5,7-triene (Pregeijerene) in Pimpinella species and chemosystematic implications
    Amsterdam : Elsevier
    Biochemical Systematics and Ecology 8 (1980), S. 39-41 
    Details
    ISSN: 0305-1978
    Keywords: Apiaceae ; Pimpinella ; chemosystematics ; essential oil ; pregeijerene
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0305-1978(80)90023-X
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  • 3
    Electronic Resource
    Electronic Resource
    Stomatal conductance and transpiration of the two faces of Acacia phyllodes (1987)
    Springer
    Trees 1 (1987), S. 110-122 
    Details
    ISSN: 1432-2285
    Keywords: Phyllodes ; Stomatal conductance ; Transpiration ; Water potential ; Acacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The daily course of stomatal conductance and transpiration was monitored on each separate face of vertical phyllodes of various acacias. The selected phyllodes had a north-south orientation so that one side faced eastwards and the other westwards. The principal measurements were made on Acacia longifolia and A. melanoxylon in Portugal in late summer and autumn, and additional measurements were made on A. ligulata and A. melanoxylon in Australia. In Portugal, irrespective of soil moisture status, conductance showed on early morning maximum with a subsequent gradual decline and sometimes a subsidiary peak in the late afternoon. Maximum conductances appeared to be a function of soil moisture status, whereas the decline in conductance in the late morning and afternoon was correlated with changes in phyllode-to-air vapour pressure deficits rather than changes in phyllode water status. The relationship of transpiration to phyllode water potential did not appear to be influenced by soil moisture status, although transpiration was less in drier soils and in the afternoons, this latter factor contributing to a marked hysteresis in the relationship. The opposing faces of the phyllodes exhibited a high degree of synchrony, showing parallel stomatal opening and closing, despite their large differences in irradiance. Stomatal conductance tended to be higher on the eastern faces in the morning and lower in the afternoon. In A. longifolia the daily average of relative conductance was much the same for both faces, but in A. melanoxylon that of the eastern face was higher and was retained even when the normal orientation of the phyllodes was reversed by turning them through 180°. Synchrony must be achieved by the stomata of both sides responding to common environmental or endogenous signals which are perceived by both surfaces with equal sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203579
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  • 4
    Electronic Resource
    Electronic Resource
    Diurnal courses of leaf conductance and transpiration of mistletoes and their hosts in Central Australia (1985)
    Springer
    Oecologia 67 (1985), S. 577-587 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Australia, diurnal courses of leaf conductance and transpiration of hemiparasitic mistletoes (Loranthaceae) and their hosts were measured using steady-state porometers under conditions of partial drought and high evaporative demand. The sites spanned a diversity of climatic regions ranging from the subtropical arid zone with winter rainfall, through the subtropical arid zone with summer rainfall to the tropical summer rainfall zone. With one exception (Acacia farnesiana with deciduous leaves), the hosts were trees or shrubs with evergreen, sclerophyllous leaves or phyllodes. The measurements confirm previous observations that mistletoes transpire at higher rates than their hosts. For adult leaves from all of the 18 different host/mistletoe pairs investigated, the daily average leaf conductances were higher in the parasites than in their hosts. The ratios ranged from 1.5 to 7.9. In the most extreme case,Amyema maidenii had a daily rate of water loss 8.9 times higher than its hostAcacia cowleana. Hoever, the parasites did not exhibit unlimited transpiration. Despite high water loss rates, leaf conductance showed large and consistent changes during the course of the day, indicating definite stomatal regulation. The typical diurnal pattern of conductance in both mistletoes and hosts consisted of an early morning peak followed by a continuous decrease throughout the remainder of the day. There was no abrupt decrease in leaf conductance of the parasites that might be interpreted as a threshold response with respect to internal water potential. In most cases, the continuous stomatal closure occurred without substantial changes in leaf water potential over a time span of several hours. The decrease in leaf conductance was correlated with an increase in leaf-to-air water vapor difference, which was associated with increasing leaf temperatures. It seems probable that external humidity plays a major role in the stomatal response. Diurnal courses of leaf conductance of the host/parasite pairs usually showed similar general patterns, even when the absolute rates were quite different. Thus, mistletoes not only control their water loss by stomatal action but this regulation seems to occur in coordination with the stomatal response of their hosts. The integrated mistletoe/host system must also endure severe drought conditions. Controlled water use is necessary for long-term survival of the host. Assuming stomatal behavior in the host is well adapted to ensure its existence, then similar performance in the mistletoe would promote survival of both host and parasite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00790030
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  • 5
    Electronic Resource
    Electronic Resource
    Mistletoes: a hypothesis concerning morphological and chemical avoidance of herbivory (1986)
    Springer
    Oecologia 70 (1986), S. 234-237 
    Details
    ISSN: 1432-1939
    Keywords: Mimicry ; Nitrogen ; Herbivory ; Mistletoe ; Australia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaves from many misletoe species in Australia strongly resemble those of their hosts. This cryptic mimicry has been hypothesized to be a means of reducing the likelihood of mistletoe herbivory by vertebrates. Leaf Kjeldahl nitrogen contents (a measure of reduced nitrogen and thus amines, amino acids and protein levels) of mistletoes and their hosts were measured on 48 mimetic and nonmimetic host-parasite pairs to evaluate hypotheses concerning the significance of crysis versus noncrypsis. The hypothesis that mistletoes mimicking host leaves should have higher leaf nitrogen levels than their hosts is supported; they may be gaining a selective advantage through crypsis (reduced herbivory). The second hypothesis that mistletoes which do not mimic their hosts should have lower leaf nitrogen levels than their hosts is also supported; they may be gaining a selective advantage through noncrypsis (reduced herbivory resulting from visual advertisement of their reduced nutritional status).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379245
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  • 6
    Electronic Resource
    Electronic Resource
    Growth patterns of the alien perennial Bunias orientalis L. (Brassicaceae) underlying its rising dominance in some native plant assemblages (1996)
    Springer
    Plant ecology 125 (1996), S. 73-82 
    Details
    ISSN: 1573-5052
    Keywords: Bunias orientalis ; Colonization ; Disturbance ; Invasion ; Regeneration ; Relative growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The polycarpic perennial Bunias orientalis L. (Brassicaceae) introduced to Central Europe in the 18th century recently entered a phase of rapid spread accompanied by sudden establishments of extensive dominance stands mainly on roadside locations. We studied vegetation structure and expansion rate of B. orientalis stands and performed a series of experiments to investigate key factors that underlie the colonizing and establishment of B. orientalis. Reiterated observations exposed a high current expansion rate of B. orientalis populations and vegetation surveys of B. orientalis stands showed that these stands were mainly composed of Artemisietea and Arrhenateretea species. Regeneration experiments with root fragments revealed high regeneration capacities: root fragments of 3 cm length showed 93% regeneration, varying water content (10–50% water loss) and separation into root cortex and root stele yielded regeneration of 30 to 50%. In a field study high regrowth after mowing with varying mowing intensity indicates B. orientalis to be well adapted to disturbed sites as its preferential locations for development of dominance stands. Vegetative growth parameters were studied in two controlled growth experiments with elevated nutrient availabilities. B. orientalis exhibited a high sensitivity to nutrient addition and rosette sizes of maximal 90 cm were reached. Biomass was comparable or even higher than that of native ruderals grown in the same experiment. Measurements of reproductive parameters revealed a high reproductive effort (0.2 to 0.45 g g-1) even under intense mowing regimes, resulting in a dense seed bank with maximal values of about 400 fruits (≅550 seeds) l-1 soil. With respect to colonization and establishment of B. orientalis the results of our study enable the formulation of three hypotheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045206
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  • 7
    Electronic Resource
    Electronic Resource
    Role of allelopathy as a possible factor associated with the rising dominance ofBunias orientalis L. (Brassicaceae) in some native plant assemblages (1996)
    Springer
    Journal of chemical ecology 22 (1996), S. 1797-1811 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; Bunias orientalis ; root exudates ; leaf litter leachates ; soil cores ; growth inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Leaf extracts ofBunias orientalis were shown to inhibit seed germination of a variety of cultivar plant species and of species cooccurring withB. orientalis in the field. Root exudate solutions and leaf litter leachates ofB. orientalis were tested for their allelopathic activity using seedling growth assays. Additionally, in comparative seedling growth assays soil cores removed from denseB. orientalis stands were tested bimonthly for elevated allelopathic effects. The impact of root exudates on seedling growth was generally weak and varied between species. Similar results were obtained for the effect ofB. orientalis leaf litter leachates on seedlings grown in sand culture relative to the effect of leaf litter leachates of a plant species mixture. When soil as a growth substrate was used, no consistent differences in seedling growth were obtained between the two litter leachate treatments. In the soil core experiment seedlings grown in soil cores collected from a denseB. orientalis stand unexpectedly showed better performance than seedlings grown in soil cores collected from a nearby mixed plant stand withoutB. orientalis, at least in early spring and late autumn. Predominating nutrient effects are, therefore, assumed to conceal a potentially increased allelopathic effect of soil beneath denseB. orientalis stands. It is concluded that other factors than allelopathy must be investigated to explain the rapid establishment of dense stands of this alien plant species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02028505
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