Fraunhofer-Institut für Atmosphärische Umweltforschung IFU

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  • Publication
    Metabolism of reduced and inorganic sulphur in pea cotyledons and distribution into developing seedlings
    ( 2002)
    Herschbach, C.
    ;
    Pilch, B.
    ;
    Tausz, M.
    ;
    Rennenberg, H.
    ;
    Grill, D.
    Sulphur export and redistribution from the cotyledons of pea (Pisum sativum) seedlings was investigated to determine the role of cotyledons as a sulphur source during root-shoot axis development. Thiols and sulphate were analysed using standard biochemical techniques, and S-35 fed to cotyledons by injection. After S-35-cysteine injection, c. 50% of the labelled S in the cotyledon was metabolized to S-35-sulphate. This reaction was partly inhibited by aminooxyacetic acid, an inhibitor of cysteine-desulfhydrase. After S-35-sulphate application, c. 1% of the radiolabel was found in cysteine and glutathione in the cotyledon. After 2 h, c. 20% of the S-35 was transported into the root-shoot axis independently of whether S-35-sulphate or S-35-cysteine was injected into the cotyledon. After 4 h, 40% of S-35 was found outside the cotyledon. Cotyledons of pea seedlings are capable of sulphate assimilation and cysteine degradation. Both sulphate and reduced sulphur were allocated from the cotyledons to the developing tissues of the pea seedlings.
  • Publication
    Assimilate transport in the xylem sap of pedunculate oak (quercus-robur) saplings
    ( 2001)
    Heizmann, U.
    ;
    Kreuzwieser, J.
    ;
    Schnitzler, J.P.
    ;
    Brüggemann, N.
    ;
    Rennenberg, H.
  • Publication
    Competition of spruce trees for substrates of microbial N2O-production and -emission in a forest ecosystem
    ( 2001)
    Rennenberg, H.
    ;
    Stoermer, H.
    ;
    Weber, P.
    ;
    Daum, M.
    ;
    Papen, H.
    Uptake of ammonium and nitrate by the roots of spruce trees at a N-limited control site and a site subjected to ammonium sulphate fertilisation with 150 kg N ha(-1) in one dose were determined shortly after and two years subsequent to the treatment. The changes in the rates of nitrogen uptake by the roots were compared with changes in microbial nitrogen conversion that are connected with the production of N2O in, and the emission of these atmospheric trace gases from soils by nitrification and denitrification. Uptake of ammonium and nitrate by the roots of the N-limited trees were low and initially were strongly enhanced by fertiliser application. This increase was mainly due to an increase in ammonium and nitrate available to the roots in. the soil-water. Two years subsequent to the fertiliser application, ammonium and nitrate contents of the soil-water were still enhanced compared to the untreated control site, but uptake of ammonium and nitrate by the spruce roots was completely shut down. At the N-limited control site competition between root uptake of inorganic N and its microbial conversion was largely in favour of root uptake by the spruce trees. The rates of nitrification and denitrification of inorganic N were minute under these conditions and appreciable N2O emission was not observed. Application of ammonium sulphate transiently enhanced both root uptake and microbial N conversion, and was connected with increased emission of N2O. In the long term, ammonium sulphate application completely inhibited ammonium and nitrate uptake by the trees, irrespective of enhanced concentrations of ammonium and nitrate in the soil-water. As a consequence, considerable amounts of inorganic N were still available for microbial conversion 2 years after fertiliser application. At this time nitrification rates were still high at the fertilised site, but the nitrate produced was not further converted by denitrification. It is assumed that nitrate produced by nitrification is subjected to microbial immobilisation. Under these conditions N2O emission from the control site and the fertilised site were low and did not differ significantly.
  • Publication
    Characterization of root exudates at different growth- stages of 10 rice (oryza-sativa l.) cultivars
    ( 2001)
    Aulakh, M.S.
    ;
    Wassmann, R.
    ;
    Bueno, C.
    ;
    Kreuzwieser, J.
    ;
    Rennenberg, H.
  • Publication
    Influence of powdery mildew (microsphaera alphitoides) on isoprene biosynthesis and emission of pedunculate oak (Quercus robur L.) leaves
    ( 2001)
    Brüggemann, N.
    ;
    Schnitzler, J.-P.
    The influence of powdery mildew (Microsphaera alphitoides.) infection on isoprene emission rate, IDP isomerase (E.C.5.3.3.2) and isoprene synthase activities as well as photosynthetic parameters of pedunculate oak (Quercus robur L.) - a dominant isoprene emitter of Central Europe - was investigated in two independent field experiments in September 1998 and 1999. In 1998 the pathogenic attack by mildew (Microsphaera alphitoides) caused serious visible damages of the leaves which were accompanied by a 50% reduction of net assimilation rate and total leaf chlorophyll content. IDP isomerase activity, isoprene synthase activity and standard isoprene emission factors were reduced by 70-80% under these conditions. In 1999 the powdery mildew infection of the oak leaves was weaker with no chlorotic and senescent leaf areas, although all infected leaves were totally covered by mycelium. In addition, none of the physiological parameters measured was significantly influenced by the Microsphaera infection. The results demonstrate that with respect to the widespread occurrence of powdery mildew on oaks during wet summer periods in some years the isoprene emission potential of oaks can be strongly affected by a serious infection with Microsphaera. This influence has to be considered for a realistic calculation of isoprene fluxes from forest vegetation.
  • Publication
    N2O and CH4-fluxes from soils of a N-limited and N-fertilized spruce forest ecosystem of the temperate zone
    ( 2001)
    Papen, H.
    ;
    Daum, M.
    ;
    Steinkamp, R.
    ;
    Butterbach-Bahl, K.
    Based on a 3-year data set from measurements of N2O fluxes from soil of a N-limited spruce forest ecosystem it could be demonstrated for the first time that such soils can function as a sink rather than a source for atmospheric N2O. The results suggest that N2O uptake from the atmosphere into the soil is catalyzed by soil denitrifiers which are able to use N2O from the atmosphere instead of nitrate as an electron acceptor for denitrification due to severe limitations of nitrate in the soil. This interpretation is in accordance with the finding that net nitrate production via nitrification was zero or only marginal in the soil of the unfertilized site. On the other hand, the results strongly indicate that atmospheric N-input - simulated in this experiment by ammonium sulfate application (150 kg N ha(-1)) to the forest soil - can lead to a change of the function of the soil of a N-limited forest ecosystem from a sink to a net source of atmospheric N2O. This change was most likely due to stimulation of N2O production via nitrification and denitrification after N-fertilization. N-fertilization lead to a partial inhibition of atmospheric CH4 oxidation. However, this inhibition lasted only short term after N-fertilization and even changed at the end of the observation period to a weak stimulation of CH4 uptake activity at the N-fertilized site when soil ammonium concentrations at this site had decreased to values which were only slightly higher as compared to the unfertilized site. This indicates that at the unfertilized site atmospheric methane oxidizers were N-limited for growth.
  • Publication
    Scanning electron microscopy analysis of the aerenchyma in two rice cultivars
    ( 2000)
    Butterbach-Bahl, K.
    ;
    Papen, H.
    ;
    Rennenberg, H.
    An zwei Reisvarietäten, die in vorangegangenen Freiland- und Labor-Untersuchungen Unterschiede in der Gastransportkapazität des Aerenchymsystems zeigten, wurden rasterelektronenmikroskopische Untersuchungen zur Beschreibung der Anatomie und Konstruktion des Aerenchymsystems in verschiedenen Pflanzenabschnitten (Wurzel, Wurzel-Spross-Übergang, Blattscheide, Blattspreite, Halm) durchgeführt. Die Untersuchungen konzentrierten sich auf die Identifizierung a) von Restriktionen des Gastransports innerhalb des pflanzlichen Aerenchyms sowie b) morphologischer Voraussetzungen für den schon früher beobachteten Gasaustausch zwischen Boden und Aerenchym bzw. Boden und Atmosphäre. Es konnten keine signifikanten Unterschiede in der räumlichen Ausdehnung bzw. der Anatomie des Aerenchyms zwischen den beiden untersuchten Reisvarietäten nachgewiesen werden.CH4-Konzentrationsmessungen in verschiedenen Sproßabschnitten zeigten, dass die Emission von CH4 aus dem pflanzlichen Aerenchym in die Atmosphäre im wesentlichen über die Blattscheiden erfolgte. Als hauptsächlicher Restriktor des Gastransports im pflanzlichen Aerenchymsystem erwiesen sich Lagen parenchymatischer Zellen (Dicke ca. 40 - 50 µm) die zwischen Wurzelaerenchym und Aerechym des Sprosses gefunden wurden. In zukünftigen Arbeiten sollten die Eigenschaften dieses den Gasaustausch innerhalb der Pflanze modulierenden Gewebeabschnitts verstärkt untersucht werden.
  • Publication
    NH3 and NO2 fluxes between beech trees and the atmosphere - correlation with climatic and physiological parameters
    ( 2000)
    Geßler, A.
    ;
    Rienks, M.
    ;
    Rennenberg, H.
    The dynamic-chamber technique was used to investigate the correlation between NH3 and NO, fluxes and different climatic and physiological parameters: air temperature; relative air humidity; photosynthetic photon fluence rate; NH3 and NO2 concentrations; transpiration rate; leaf conductance for water vapour; and photosynthetic activity. The experiments were performed with twigs from the sun crown of mature beech trees (Fagus sylvatica) at a field site (Höglwald, Germany), and with 12-wk-old beech seedlings under controlled conditions. Both sets of experiments showed that NO2 and NH3 fluxes depended linearly on NO2 and NH3 concentration, respectively, in the concentration ranges representative for the field site studied, and on watervapour conductance as a measure for stomatal aperture. The NO2 compensation point determined in the field studies (the atmospheric NO2 concentration with no net NO2 flux) was 1.8-1.9 nmol mol high -1, The NH3 compensation point varied between 3.3 and 3.5 nmol mol high -1, in the field experiments, and was 3.0 nmol mol -1 in the experiments under controlled conditions. The climatic factors T and PPFR were found to influence both NO2 and NH3 fluxes indirectly, by changing stomatal conductance. Whilst NO2 flux showed a response to changing relative humidity that could be explained by altered stomatal conductance, increased NH3 flux with increasing relative humidity (> 50 %) depended on other factors. The exchange of NO2 between above-ground parts of beech trees and the atmosphere could be explained exclusively by uptake or emission of NO2 through the stomata, as indicated by the quotient between measured and predicted NO2 conductance of approx. 1 under all environmental conditions examined. Neither internal mesophyll resistances nor additional sinks could be observed for adult trees or for beech seedlings. By contrast, the patterns of NH3 flux could not be explained by an exclusive exchange of NH3 through the stomata. Deposition into additional sinks on the leaf surface, as indicated by an increase in the quotient between measured and predicted NH3 conductance, gained importance in high air humidity, when the stomata were closed or nearly closed and/or when atmospheric NH3 concentrations were high. Although patterns of NH3 gas exchange did not differ between different months or years at high NH3 concentrations (c. 140 nmol mol high -1), it must be assumed that emission or deposition fluxes at low ambient NH3 concentration (0.8 and 4.5 nmol mol high -1) might vary significantly with time because of variation in the NH3 compensation point.
  • Publication
    Pattern and amount of aerenchyma relate to variable methane transport capacity of different rice cultivars
    ( 2000)
    Aulakh, M.S.
    ;
    Wassmann, R.
    ;
    Rennenberg, H.
    ;
    Fink, S.
    Aerenchyma, developed in both root and aboveground parts of rice plants, is predominantly responsible for plant-mediated transfer of methane (CH4) form the soil to the atmosphere. To clarify the pathways of CH4 transport through the rice plant and find differences that may determine the large variation in the patterns of methane transport capacity (MTC) of rice cultivars, we examined the appearance, the distribution pattern, and the density of aerenchyma in different parts of rice plants of three widely varying rice cultivars during panicle initiation, flowering, and maturity stages. The data on the amount and density of small (> 1 x 10 high 3 - 10 high 3 µm high 2), medium (> 5 x 10 high 3 - 20 x 10 high 3 µm high 2), and large aerenchyma lacunae (> 20 x 10 high 3 µm high 2) were collected using a computer assisted image-analyzing system. The brightfield optical microscopy of roots of all tested rice plants demonstrated the continuity of aerenchyma channels in the roots that function as conduits for bi-directional transport of gases. The aerenchyma channels of primary roots showed direct connection with those of culms. Intercalary meristems were found at the transition zone of rootculm aerenchyma connections. Well-developed aerenchyma lacunae present in the internodal region of the culm base were uniformly distributed in the peripheral contical zone. The nodal region had relatively fewer and smaller aerenchyma lacunae that showed a non-uniform distribution pattern. As a result, few aerenchyma channels continued from the internodal region through to the nodal region. The aerenchyma in the cortex zone of the culm expanded along with the growing secondary tiller, development continuity between the culm and the secondary tiller. The micrographs of longitudinal sections of different specimens of culm-leaf sheath intersection showed the continuity of aerenchyma channels from the culm to the leaf. The amount of medium and large aerenchyma lacunae in the leaf sheath was respectively 2 and 33 times greater as compared to those of the tiller. The proportion of the large lacunae in the total amount of aerenchyma in leaf sheath was 75 % as compared to only 8 % in the tiller, revealing higher number and larger size of aerenchyma in the former. There were significant differences in amount and density of aerenchyma between individual cultivars at a given growth stage, as well as in the development patterns. While the amount and density of medium and small aerenchyma lacunae in the internodal region of the culm base did not show any relationship with MTC of rice cultivars, large aerenchyma lacunae exhibited highly significant correlations with MTC of different cultivars, suggesting that the wide variation in MTC of rice plants during different growth stages are related to these structural features.