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  • Catharanthus roseus  (3)
  • Fire intensity  (3)
  • Induction  (3)
  • Springer  (9)
  • 1
    ISSN: 1432-1939
    Keywords: Fire intensity ; Adenostoma fasciculatum ; Lignotuber ; Resprouting ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the population structure of the lignotuberous resprouter Adenostoma fasciculatum were investigated by experimentally burning at various intensities an old stand in southern California chaparral. Survival after fire, time of resprouting, herbivory, and survival after resprouting were monitored for more than 1 year after the fire. Greater fire intensity increased plant mortality and the size of plants that died as a consequence of the fire. Time from the fire until resprouting increased with increasing fire intensity and was related to plant size: the larger the plants the earlier they resprouted. Post-resprouting mortality also increased with fire intensity and was related to time of resprouting. Herbivory increased with fire intensity and the size of plants affected by it changed with the intensity of the fire. Fire intensity had profound direct and indirect effects on the population structure of Adenostoma fasciculatum. Plant size strongly determined the direct and indirect lethal effects of fire.
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  • 2
    ISSN: 1432-1939
    Keywords: Adenostoma fasciculatum ; California chaparral ; Fire intensity ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Resprouting is the main regeneration mechanism after fire in Mediterranean-type ecosystems. Herbivores play an important role in controlling postfire seedling establishment, but their influence on regeneration by resprouting is less well known. To study the effects of fire intensity on resprouting of Adenostoma fasciculatum in southern California chaparral, and its interaction with herbivory, we conducted an experimental burn at three levels of fire intensity. We found that increasing fire intensity increased plant mortality, reduced the number of resprouts per plant, and delayed the time of resprouting. Herbivory increased with fire intensity, and was related to the time of resprouting. Plants resprouting later in the season and out of synchrony with the main flush were attacked more readily by herbivores. Post-resprouting mortality also increased with fire intensity and was significantly associated with herbivory in the higher fire intensity plots. Fire intensity effects on chaparral regeneration by resprouting may be farreaching through effects on the population structure, resprout production, and growth of Adenostoma fasciculatum.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-072X
    Keywords: Isocitrate lyase ; Induction ; Catabolite repression ; Catabolite inactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The synthesis of isocitrate lyase was induced by the presence of ethanol in the chemostat reaching a specific activity of 200 mU·mg-1 at this induced state. In glucoselimited, derepressed cells, 20 mU·mg-1 were detected and under repressed conditions isocitrate lyase activity was not detected. The sensitivity of gluconeogenic enzymes: cytoplasmic malate dehydrogenase; fructose 1,6-bisphosphatase and isocitrate lyase as well as the mitochondrial enzymes NADH dehydrogenase and succinate cytochrome c oxidase to glucose and galactose repression were studied in chemostat cultures. Our results show that galactose was less effective as a repressor than glucose. Malate dehydrogenase was completely inactivated by glucose, whereas galactose only produced a 78% decrease of specific activity. Fructose 1,6-bisphosphatase and isocitrate lyase were completely inactivated by both sugars but at different rate. Glucose produced an 85% decrease of specific activity of the mitochondrial enzymes whereas galactose only decrease an 67%.
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  • 4
    ISSN: 1432-072X
    Keywords: Induction ; Catabolic repression ; galactose metabolism ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Induction and repression kinetics of alphagalactosidase, galactose uptake system and Leloir pathway enzymes were studied in chemostat cultures by changing the medium feed from glucose (11 mM) to glucose and galactose (11 mM; 17 mM respectively) in the induction experiments; and from galactose (11 mM) or (111 mM) to galactose plus glucose (83 mM) in the repression experiments. Basal levels of alpha-galactosidase and glucose uptake could be estimated in glucose-limited yeast cells, but it was not possible to detect any glactose pathway enzyme activity. In the repression experiments under galactose-limited or galactose-sufficient yeast cells, alpha-galactosidase and galactokinase decayed with K d=-0.21h-1=-D; that is, synthesis of these enzymes ceased (catabolite repression). In contrast transferase and epimerase activities and galactose uptake, decreased with K d values of-0.33 and-0.54h-1, showing that these activities were also subject to catabolite inactivation.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 107 (1981), S. 189-194 
    ISSN: 1615-6102
    Keywords: Haemanthus katberinae Bak ; Induction ; Chromosome condensation ; Mitosis ; Time-lapse cinematography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The presence of a prophase nucleus inHaemanthus endosperm happens to trigger the break down of the nuclear envelope in any interphase nucleus, located in its close proximity. Besides, chromosomes in the interphase nucleus start condensing gradually for the initial breaking point which is the nearest point to the prophase. The observation suggest the diffusion of an inducer, whose progression has been recorded to occur at a rate of 1.1 μm/min.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 139 (1998), S. 91-101 
    ISSN: 1573-5052
    Keywords: Cytisus sp. ; Fire behavior ; Fire intensity ; Fire severity ; Heat output per unit area ; Mediterranean-type shrublands ; Minimum branch diameter ; Open-calorimeters ; Pyrometers ; Spain ; Temperature-residence-time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methods are presented to relate temperature-residence-time at the soil surface, i.e., time above 150 ºC as an estimation of the severity of a fire, with measurements made during an experimental fire or on two post hoc measurements. The experiment was carried out in a shrubland dominated by the woody-legume Cytisus striatus subsp. eriocarpus, in Central Spain. Temperature-sensitive paints, and steam-releasing open-calorimeters were used as fire-meters during the burn. Post hoc measurements used were estimations of heat output per unit area, and measurements of the minimum diameter of branches of Cytisus remaining after the fire. Time above 150 ºC was obtained from measurements made with thermocouples placed at the soil surface in 20 contiguous 1×1 m squares of the burn plot. All other measurements were made at each 1×1 m in the 22×3 m rectangle surrounding, and including, the thermocouple squares. Various simple and multiple regression models were constructed to predict time above 150 ºC from each of the four measurements made during or after the fire. Maximum coefficients of determination obtained for regressions were 0.61 and 0.62 for water mass loss from open-calorimeters and branch diameter, respectively. Using all the variables in a multiple regression model, time above 150 ºC was related to water mass loss from open-calorimeters and heat output per unit area with a coefficient of determination of 0.77. It is concluded that estimations of time above 150 ºC at the soil surface during the passage of fire may be possible based on simple devices, such as open-calorimeters, or on biological indicators, such as minimum branch diameters. Additionally, combining two methods (open-calorimeters, estimations of heat output per unit area) may allow the reconstruction of the time above 150 ºC during the fire at a scale of 1 2, an important characteristic of a burn to understand ecosystem response to fire.
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  • 7
    ISSN: 1573-5044
    Keywords: Ajmalicine ; bioreactor ; Catharanthus roseus ; growth model ; scale-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The productivity of a cell culture for the production of a secondary metabolite is defined by three factors: specific growth rate, specific product formation rate, and biomass concentration during production. The effect of scaling-up from shake flask to bioreactor on growth and production and the effect of increasing the biomass concentration were investigated for the production of ajmalicine by Catharanthus roseus cell suspensions. Growth of biomass was not affected by the type of culture vessel. Growth, carbohydrate storage, glucose and oxygen consumption, and the carbon dioxide production could be predicted rather well by a structured model with the internal phosphate and the external glucose concentration as the controlling factors. The production of ajmalicine on production medium in a shake flask was not reproduced in a bioreactor. The production could be restored by creating a gas regime in the bioreactor comparable to that in a shake flask. Increasing the biomass concentration both in a shake flask and in a stirred fermenter decreased the ajmalicine production rate. This effect could be removed partly by controlling the oxygen concentration in the more dense culture at 85% air saturation.
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  • 8
    ISSN: 1573-5044
    Keywords: Ajmalicine ; alkaloids ; catharanthine ; Catharanthus roseus ; hairy roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two year old, transformed root cultures of Catharanthus roseus accumulate ajmalicine and catharanthine (0.57 and 0.36 mg g-1 DW, or 7.0 and 3.0 mg l-1, respectively). Changes in the concentration of the medium components, as well as the addition of hydrolytic enzymes and biotic elicitors, were used as strategies to increase these alkaloid yields. Regarding the components of the medium, the results obtained, when sucrose was raised from 3 to 4.5%, are noteworthy. The nitrogen source induced differential responses in the individual alkaloid yields. No net change in the alkaloid content was observed either with changes in the concentration of vitamins or macro-and micronutrients. Though the root culture only shows a limited response to elicitors, Aspergillus treatment and the use of macerozyme increased the accumulation of ajmalicine selectively, while the addition of methyl jasmonate increased the yield of both alkaloids.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell, tissue and organ culture 42 (1995), S. 1-25 
    ISSN: 1573-5044
    Keywords: Biosynthesis ; Catharanthus roseus ; cell culture ; indole alkaloids ; large-scale production ; review ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The literature concerning the regulation and the biosynthesis of secondary metabolites in cell and tissue cultures of Catharanthus roseus is reviewed. The aim of this review is to summarise the progress achieved since the previous review of this subject from 1988 to December 1993. Several factors influencing the production of indole alkaloids are discussed. Special attention is given to large-scale cultivation methods. Some economic considerations on the production of ajmalicine are also discussed.
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