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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The above-ground parts of two years old seedlings of Douglas fir (Pseudotsuga menziesii) were exposed to filtered air, NH3, NO2+, SO2 (66, 96 and 95 μg m−3, respectively), to a mixture of NO2+NH3 (55 + 82 μg m−3) or SO2+NO2 (128 + 129 μg m−3), for 8 months in fumigation chambers. Both chlorophyll fluorescence and gas exchange measurements were carried out on shoots which had sprouted at the beginning of the exposure period. The chlorophyll fluorescence measurements were performed after 3 and 5 months of exposure (average shoot age 70 and 140 days, respectively). Light response curves of electron transport rate (J) were determined, in which J was deduced from chlorophyll fluorescence. In addition, light response curves of net CO2 assimilation were determined after 5 months of exposure. After 3 months of exposure (average shoot age 70 days) all exposure treatments showed a lower maximum electron transport rate (Jmax) as compared to the control shoots (filtered air). A large reduction (45%) was observed for shoots exposed to SO2+NO2. During the exposure period between 3 and 5 months (average shoot age 70 and 140 days, respectively) a decrease of Jmax was observed for all treatments. Jmax had further declined some time after termination of the exposure, when average shoot age was 310 days.Shoots exposed to SO2 and SO2+NO2 also showed a reduction in maximum net CO2 assimilation (Pmax) as compared to the control shoots. However, shoots exposed to NO2 showed no reduction and even a higher Pmax was observed for shoots exposed to NH3 or NO2+NH3. Needles of these treatments also showed a higher chlorophyll content which might explain the contradictory results obtained for these treatments: the increased amount of photosynthetic units counteracts the reduction in Jmax and consequently no reduction in Pmax is measured. Shoots exposed to SO2 and SO2+NO2 also showed a reduction in maximum stomatal conductance (gs). However, the stomatal opening was larger than could be expected on basis of their (maximum) CO2 assimilation rate. Consequently, water use efficiency of these shoots was lower than that of the control shoots. Also shoots exposed to NO2 had a lower water use efficiency due to a significantly higher maximum gs. Shoots exposed to NH3 showed a high transpiration rate in the dark, indicating imperfect stomatal closure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Three years old seedlings of Douglas fir (Pseudotsuga menziesii) were exposed lo filtered air, O3 (day and night concentrations of 78 and 30 μgm−3: respectively). NH3 (54 μg m−3) and to a mixture of NH3+O3 (day and night concentrations of 49 + 83 and 49 + 44 μg m−3 respectively), for 5 months in fumigation chambers. Both gas exchange and chlorophyll fluorescence were measured on shoots which had sprouted at the beginning of the exposure period. After 4. 8, 10 and 20 weeks of exposure, light response curves of electron transport rate (J) were determined, in which J was deduced from chlorophyll fluorescence. Net CO2 assimiialion was measured at maximum light intensity of 560) μmol m−2 S−1 (Pn.560). After 8 and 10 weeks of exposure also light response curves of CO2 assimilation were assessed.Shoots exposed to O3 showed a reduction in net CO2 assimilation as compared to the control shoots during the entire exposure period. The reduction was related lo a lower chlorophyll content and a lower electron transport rate, whereas no effect on quantum yield efficiency (qy) was observed. In contrast, shoots exposed to NH3 showed a positive effect on photosynthesis. Shoots exposed to NH3. + O3 showed a rapid increase in Pn.560, in the period between 4 and 8 weeks to a level equal of that of the NH3-treatment. After this period a decline in Pn.560 was observed.After 10 weeks of exposure shoots exposed to O3 showed an increased transpiration rate in the dark as compared to the control shoots. In addition, water use efficiency (WUE) declined as a result of an increase in leaf conductance. Both observations indicate that the stomatal apparatus was affected by O3. A high transpiration rate in the dark was also found for shoots esposed to NHX. However, shoots exposed to NH3+ O3 showed neither an effect on WUE, nor an effect on transpiration rate in the dark. The possibility that NH3 delayed the O3 induced effects on photosynthesis and stomatal conductance is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 43 (1978), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of cytokinins was studied on the incorporation of 14C-labelled precursors into the nucleic acid fraction of protoplasts isolated from callus or roots of Brassica campestris. Protoplasts from callus and roots took up 14C-uridine from the incubation medium and incorporated this precursor into the ribonucleic acid fraction during the experimental period of 16 h. Low concentrations of kinetin (10−8-5 × 10−6M) did not stimulate the incorporation, and kinetin inhibited this process at higher concentrations (5 × 10−5M). This result led to an investigation on the uptake of cytokinins by protoplasts of roots. In contrast to a rapid uptake of radio-actively labelled adenine and uridine. protoplasts from roots took up only small amounts of labelled kinetin. zeatin, zeatin riboside and zeatin nucleotides from the incubation medium.Root sections took up far more adenine and kinetin than protoplasts from roots. The ratio between the amount of kinetin taken up and applied was much higher for the sections than for protoplasts, indicating that intact root cells took up kinetin far more rapidly than protoplasts. It is suggested that the plasmalemma and cell wall play an essential role in the uptake of cytokinins or that the differences in the uptake rates are related to differences between the rates of metabolism of cytokinins in root sections and in protoplasts.
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  • 4
    ISSN: 1432-2048
    Keywords: Agrobacterium ; Brassica (transformed plants) ; Genetic manipulation ; Osmotic pressure ; Potassium ; Solanum (transformed plants)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth, water content, osmotic pressure and solute content were examined for normal potato (Solanum tuberosum L. cv. Desiree) and a derivative (line D9X8a), which was genetically transformed with TL-DNA from Agrobacterium rhizogenes. Plants were grown (i) in vitro, (ii) in a growth chamber and (iii) in the field. In vitro, the transformed potato plants produced more biomass than the untransformed plants, partly because they had a higher water content. Potassium concentration and osmotic pressure were lower in cell sap extracted from the transformed potato shoots. In some cases the difference was as much as 50%. These differences were less clear, absent or reversed in plants from a growth chamber or from the field. In the field, however, transformed potato senesced early. It is suggested that a cellular basis for these observations may be changes induced by Ri TL-DNA expression products in plant membrane properties.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Potato research 29 (1986), S. 367-379 
    ISSN: 1871-4528
    Keywords: hairy-root ; Ri-plasmid ; T-DNA ; potato cultivars ; in vitro culture ; field experiments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Infektion verwundeter Stengel in vitrogewachsenen Kartoffelsorten hatte lokale, proliferierende Wurzelbildung (haarige Wurzeln; Abb. 2A) zur Folge. Diese Wurzelzellen enthielten neu eingebrachte DNA, die nicht in normalen Kartoffeln entdeckt werden konnte, sondern aufA. rhizogenes zurückzuführen ist (Mechanismen vgl. Abb. 1). Einzelne umgebildete Wurzeln der Sorten Majestic, Record und Maris Bard wurden zu ganzen Pflanzen regeneriert (Abb. 2B, C). Die meisten der transformierten Pflanzen waren euploid (2n=4x=48; Abb. 2D). Der Ausdruck der eingebrachten Gene ergab stabile Veränderungen bei Pflanzenentwicklung und Knollengestalt (Abb. 2E), welche auch unter Feldbedingungen erhalten blieben (Abb. 2F, 3 und Tabelle 1). Daraus wurde geschlossen, dass (1) vermutlich jede kommerzielle Kartoffelsorte unter entsprechenden BedingungenAgrobacterium-vermittelter genetischer Veränderung zugänglich ist; (2) die vonA. rhizogenes abstammenden Gene konventionelle Modellgene zum Studium des Ausdrucks von Struktur, Kontrolle und Stabilität transferierter Gene sind; und (3) vonA. rhizogenes abstammende Gene von potentiellem Nutzen zum Studium des Einflusses spezifischer genetischer Faktoren auf komplexer biologischer Prozesse wie Knollenentwicklung und Knollenbildung sind. Vielleicht können Gene, wie die vonA. rhizogenes abgeleiteten T-DNA-Gene, welche kontrollierenden Einfluss auf die Pflanzenentwicklung und Knollenbildung zeigen, zur Hervorbringung von nützlichen Änderungen, die für bestimmte Kartoffellinien von Nutzen sind, verwendet werden.
    Abstract: Résumé L'infection de tiges blessées de variétés de pommes de terre cultivées in vitro avecAgrobacterium rhizogenes a causé une prolifération localisée de racines (racines chevelues, Fig. 2A). Les cellules de ces racines contenaient du DNA nouvellement introduit, non décelable chez la pomme de terre non infectée, provenant deA. rhizogenes (pour le mécanisme voir Fig. 1). De simples racines modifiées génétiquement, issues des variétés Majestic, Record et Maris Bard, régénéraient des plantes entières (Fig. 2B-C). La plupart des plantes régénérées étaient euploïdes 2n=4x=48 (Fig. 2D): les gênes introduits s'exprimaient par des modifications stables au niveau du développement de la plante et de la forme des tubercules (Fig. 2E), même dans les conditions du champ (Fig. 2F, 3 et tableau 1). On en concluait que (i) probablement n'importe quelle variété commerciale cultivée dans des conditions appropriées peut être soumise à des manipulations avecAgrobacterium comme médiateur; (ii) les gênes provenant deA. rhizogenes sont des modèles génétiques possibles pour étudier les questions concernant la structure, le contrôle et la stabilité de l'expression des gênes transférés. En outre, (iii) les gênes provenant d'A. rhizogenes constituent un matériel potentiel pour étudier l'influence des facteurs génétiques spécifiques sur des processus biologiques complexes tels que la croissance et la tubérisation de la pomme de terre. Peut être que des gênes semblables aux gênes T-DNA deA. rhizogenes ont une influence sur le développement de la plante; peut être aussi que leur introduction occasionnerait des modifications bénéfiques, en particulier pour les lignées de pomme de terre.
    Notes: Summary Infection withAgrobacterium rhizogenes of wounded stems of potato cultivars grown in vitro caused localized prolific root formation (hairy-roots). The cells of these roots contained newly introduced DNA, not detected in normal potato, that was derived fromA. rhizogenes. Single transformed roots from the cultivars Majestic, Record and Maris Bard were regenerated into whole plants. Expression of the introduced genes caused stable alterations in plant development and tuber shape, which were retained under field conditions. The following conclusions were reached. (i) Probably any commercial potato cultivar, cultured under appropriate conditions, is amenable toA. rhizogenes-mediated genetic manipulation. (ii) TheA. rhizogenes-derived genes are convenient model genes for studying questions on structure and expression of transferred genes. (iii) A. rhizogenes-derived genes are of potential use to study the influence of specific genetic factors on complex biological processes such as potato development and tuberization.
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