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
    Sulfur cycling of intertidal Wadden Sea sediments (Königshafen, Island of Sylt, Germany): Sulfate reduction and sulfur gas emission
    ( 2000)
    Kristensen, E.
    ;
    Bodenbender, J.
    ;
    Jensen, M.H.
    ;
    Rennenberg, H.
    ;
    Jensen, K.M.
    Sulfate reduction rates (SRR sub t) and reduced inorganic sulfur pools (RIS) in Wadden Sea sediment as well as sulfur gas emissions directly to the atmosphere were measured at intervals of 2 to 12 months from 1991 to 1994. Three stations were chosen in the intertidal embayment, Königshafen, representing the range of sediments found in the Wadden Sea: Organic-poor and Arenicola marina inhabited medium sand, and organic-rich muddy sand. Maximum SRR sub t were 2 to 5 times higher in muddy sand than in the sandy sediments. The depth-integrated SRR sub t varied 12 to 13-fold on a seasonal basis at the three stations. Although temperature controls biochemical processes. the overall control is more complex due to the simultaneous influence of other seasonal factors such as availability of organic matter and oxidation level of surface sediment. The sedimentary RIS pools were low due to iron limitation and contained only 30 % acid volatile sulfur (AVS). Muddy sand had up to an order of magnitude more RIS than the two sandy sediments. The turnover of RIS was rapid (turnover time from ~ 1 to 32 h), fastest during summer and at the sandy stations. The emission of S-gases was dominated by H2S during summer (45 - 67 % of the total). and was highest in muddy and lowest in coarse sand. H2S was less important in early spring (3 - 49 % of the total). Other sulfur gases, such as COS, DMS and CS2, each accounted for less than 20 % of the total sulfur emissions with no specific temporal and spatial pattern. Due to the low content of metals in the sediment. the reduced sulfur pools are cycled rapidly with chemical and biological reoxidation at oxic-anoxic boundaries as a major sink. Thus. the emissions of H2S account for less than l of the sulfide produced.
  • Publication
    Characterization of methane emissions from rice fields in Asia. II. Differences among irrigated, rainfed, and deepwater rice
    ( 2000)
    Wassmann, R.
    ;
    Neue, H.U.
    ;
    Lantin, R.S.
    ;
    Makarim, K.
    ;
    Chareonsilp, N.
    ;
    Buendia, L.V.
    ;
    Rennenberg, H.
    Methane (CH sub4) emission rates were recorded automatically using the closed chamber technique in major rice-growing areas of Southeast Asia. The three experimental sites covered different ecosystems of wetland rice -irrigated, rainfed, and deepwater rice - using only mineral fertilizers (for this comparison). In Jakenan (Indonesia), the local water regime in rainfed rice encompassed a gradual increase (wet season) and a gradual decrease (dry season) in floodwater levels. Emissions rates accumulated to 52 and 91 kg CH sub 4 ha high -1 season high -1 corresponding to approximately 40 % of emissions from irrigated rice in each season. Distinct drainage periods within the season can drastically reduce Ch sub 4 emissions to less than 30 kg CH sub 4 ha high -1 season high -1 as shown in Los Banos (Philippines). The reduction effect of this water regime as compared with irrigated rice varied from 20 % to 80 % from season to season. Methane fluxes from deepwater rice in Prachinburi (Thailand) were lower than from irrigated rice but accumulated to equally high seasonal values, i. e., about 99 kg CH sub 4 ha high -1 season high -1, due to longer seasons and assured periods of flooding. Rice ecosystems with continuous flooding were characterized by anaerobic conditions in the soil. These conditions commonly found in irrigated and deepwater rice favored CH sub 4 emissions. Temporary aeration of flooded rice soils. which is generic in rainfed rice, reduced emission rates due to low CH sub 4 production and high CH sub 4 oxidation. Based on these findings and the global distribution of rice area, irrigated rice accounts globally for 70 - 80 % of CH sub 4 from the global rice area. Rainfed rice (about 15 %) and deepwater rice (about 10 %) have much lower shares. In turn, irrigated rice represents the most promising target for mitigation strategies. Proper water management could reduce CH sub 4 emission without affecting yields.
  • 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
    Methane transport capacity of rice plants. II. Variations among different rice cultivars and relationship with morphological characteristics
    ( 2000)
    Aulakh, M.S.
    ;
    Bodenbender, J.
    ;
    Wassmann, R.
    ;
    Rennenberg, H.
    Of the total methane (CH4) emitted from a rice field during the growing season, 60 - 90 % is emitted through the rice plants. We determined the methane transport capacity (MTC) of rice plants at different physiological growth stages using an automatic measuring system under greenhouse conditions. A total of 12 cultivars (10 inbred varieties and 2 hybrids) were studied in sets of tow experiments and was distinguished into three groups according to the pattern of MTC development. MTC is generally increasing from seedling stage to panicle initiation (PI), but differs in the development from PI to maturity. While the hybrid showed a gradual increase in MTC, the inbred cultivars showed either minor changes in MTC or a drastic decrease from flowering to maturity. Among tall cultivars, Dular showed the highest MTC, followed by B40; the lowest MTC was found in Intan. High-yielding dwarf cultivars showed MTC in the descending order of IR72 > IR52 > IR64 > PSBRc 20. New plant type cultivars showed very low MTC with IR65600 exhibiting the smallest MTC at PI, flowering, and maturity. Hybrids (Magat and APHR 2) showed the largest MTC that continued to increase with plant growth. The MTC patterns were attributed to growth parameters and the development of morphological characteristics of the aerenchyma. These results suggest that in tall, dwarf, and NPT cultivars, increase in root or aboveground biomass during initial growth determines a corresponding increase in MTC. Once aerenchyma has fully developed, further increase in plant biomass would not influence MTC. However, in the case of hybrids, a positive relationship of MTC with root + shoot biomass (r = 0.672, p > 0.05) and a total plant biomass including grain (r = 0.849, p > 0.01) indicate continuous development of aerenchyma with plant growth, resulting in enhanced MTC. In all cultivars, tiller number, but not height, was linearly related to MTC, indicating that the number of outlets/channels rather than plant size/biomass determines the transport of CH4. These results clearly demonstrate that rice cultivars differ significantly in MTC. Therefore, the use of high-yielding cultivars with low MTC (for example, PSBRc 20, IR65598, and IR65600) could be an economically feasible, environmentally sound, and promising approach to mitigate CH4 emissions from rice fields.
  • Publication
    Characterization of methane emissions from rice fields in Asia. I. Comparison among field sites in five countries
    ( 2000)
    Wassmann, R.
    ;
    Neue, H.U.
    ;
    Lantin, R.S.
    ;
    Buendia, L.V.
    ;
    Rennenberg, H.
    The Interregional Research Program on Methane Emissions from Rice Fields established a network of eight measuring stations in five Asian countries. These stations covered different environments and encompassed varying practices in crop management. All stations were equipped with a closed chamber system designed for frequent sampling and long-term measurements of emission rates. Even under identical treatment - e. g., continuous flooding and no organic fertilizers - average emission rates varied from 15 to 200 kg CH sub 4 ha high -1 season high -1. Low temperatures limited CH sub 4 emissions in temperate and subtropical stations such as northern China and northern India. Differences observed under given climates, (e. g., within the tropics) indicated the importance of soil properties in regulating the CH sub 4 emission potential. However, local variations in crop management superseded the impact o soil- and climate-related factors. This resulted in uniformly high emission rates of about 300 kg CH sub 4 ha high -1 season high -1 for the irrigated rice stations in the Philippines (Maligaya) and China (Beijing and Hangzhou). The station in northern India (Delhi) was characterized by exceptionally low emission rates of less than 20 kg CH sub 4 ha high -1 season high -1 under local practice. These findings also suggest opportunities for reducing CH sub 4 emission through a deliberate modification of cultural practice for most irrigated rice fields.