Elisabeth Görge

Legume root metabolites and VA-mycorrhiza development

Summary The communication by phenylpropane-metabolites between symbiotic microorganisms and their legume host plants was further studied by the elucidation of root segment-specific exudation of aromatic compounds. The excreted flavonoids were collected by blotting seedling roots directly onto cellulose acetate filters. The flavonoids were eluted from filter segments and subsequently analysed by capillary electrophoresis. Effects of various flavonoids on VA-mycorrhiza (VAM) development were studieti. Glomus mosseae and Glomus intraradix (Schenck and Perez, 1990) were used in these studies. Daidzein (2 to 5 µM) increased germination of spores in a period between 15 to 30 days. Myricetin increased hyphal growth of germinated spores at a concentration of 2 µM between 20 and 50 days. Quercetin had a similar effect in a concentration range of 0.8 to 2.0 µM, whereas 5 µM slightly inhibited the growth of hyphae from the germinating spores. Phytoalexin production in VA-mycorrhiza infected legume roots was studied with Vicia faba by wyerone concentration to quantify the reaction of a non-aromatic secondary root metabolite. VAM infected roots increased wyerone concentration by a factor of 3 to 5 compared with the control, however, at a very low absolute level. A phenylpropane-communication concept for Rhizobium infected legumes is discussed in relation to a still incomplete similar scheme for VAM.

Uptake and metabolism of 2,4,6-trinitrotoluene in higher plants

The fate of the explosive 2,4,6-TNT in plants is of major interest. Therefore, a method was developed to analyse TNT and derivatives in plant tissue. The method was utilized to investigate the uptake and metabolism of TNT inMedicago sativa andAllium schoenoprasum grown in hydroponic cultures containing TNT levels of 0.1 to 10 mg/1. Detectable concentrations of nitrotoluenes were significantly higher inAllium schoenoprasum than inMedicago sativa. The uptake of TNT in plants was directly related to the initial TNT level. The principal nitroaromatic components in roots and shoots of both plant species were identified as 4-ADNT and 2-ADNT in equal amounts, with substantially less TNT.

Aufnahme von 2,4,6-Trinitrotoluol in Pflanzen

ZusammenfassungBodenbelastungen mit dem Sprengstoff 2,4,6-Trinitrotoluol stellen ein großes Problem auf vielen ehemaligen Rüstungsstandorten in Deutschland dar. Doch über das Verhalten von TNT im Boden und der potentiellen Aufnahme in Pflanzen ist nur wenig bekannt.Während der Vegetationsperiode 1992 wurde das Transfer-und Akkumulationsverhalten von TNT, der Reduktionsprodukte 4-ADNT und 2-ADNT und der Vorstufen 2,6-DNT und 2,4-DNT an acht ausgewählten Nahrungs-und Futterpflanzen untersucht. Die Versuche wurden auf drei unterschiedlich kontaminierten Flächen auf dem Gelände eines ehemaligen Rüstungsstandortes in Stadtallendorf/Hessen durchgeführt.Auf der hochkontaminierten Fläche unterlag die Belastung des Bodens im Bereich der Rhizosphäre Veränderungen hinsichtlich der Belastungshöhe und des Schadstoffspektrums.Es konnte ein Transfer von Nitroaromaten in die Pflanze nachgewiesen werden. Die nachweisbare Schadstoffmenge in Pflanzen war abhängig von der Schadstoffkonzentration im Boden und sowohl spezifisch für verschiedene Pflanzenorgane als auch Pflanzenarten. Das Schadstoffspektrum in Pflanzen war stets signifikant verschieden von dem Schadstoffspektrum des Bodens. Nach saurer Hydrolyse wurden in Extrakten von Bohnenwurzeln signifikante Mengen von 2,6-DNT und 2,4-DNT nachgewiesen.AbstractSoil contaminations with the explosive 2,4,6-TNT are a major problem at many sites of former ammuniton plants in Germany. But only little is known about its environmental or metabolic fate in soil or plants.A field study was conducted on a former ammunition plant in Stadtallendorf/Hessen. Three areas with different TNT concentrations were planted with 8 different crops. After harvest plants were analyzed for TNT, ADNTs and DNTs.Soil contamination decreased in the rhizosphere compared to unplanted areas and there was a transfer of TNT from soil to the plants. Accumulation in plants was dependent on soil contamination and also specific for different plant parts or plant species. The contamination spectrum of TNT and derivatives was different in soil or plant tissue, respectively. After acid hydrolysis of bean roots, 2,6-DNT and 2,4-DNT could be identified in the extract.

Competitiveness and communication for effective inoculation byRhizobium, Bradyrhizobium and vesicular-arbuscular mycorrhiza fungi

After a short summary on the ecology and rhizosphere biology of symbiotic bacteria and vesicular-arbuscular (VA) mycorrhiza fungi and their application as microbial inocula, results on competitiveness and communication are summarized. Stress factors such as high temperature, low soil pH, aluminium concentrations and phytoalexins produced by the host plants were studied withRhizobium leguminosarum bv.phaseoli andRhizobium tropici onPhaseolus beans. Quantitative data for competitiveness were obtained by usinggus + (glucoronidase) labelled strains, which produce blue-coloured nodules. ForPhaseolus-nodulating rhizobia, a group specific DNA probe was also developed, which did not hybridize with more than 20 other common soil and rhizosphere bacteria. Results from several laboratories contributing to knowledge of signal exchange and communication in theRhizobium/Bradyrhizobium legume system are summarized in a new scheme, including also defense reactions at the early stages of legume nodule initiation. Stimulating effects of flavonoids on germination and growth of VA mycorrhiza fungi were also found. A constitutive antifungal compound in pea roots, β-isoxazolinonyl-alanine, was characterized.

Biologische Sanierung von Rüstungsaltlasten

ZusammenfassungViele chemalige Rüstungsstandorte sind mit dem Sprengstoff 2,4,6-Trinitrotoluol sowie dessen Derivaten und Abbauprodukten kontaminiert. Solche Nitroaromaten besitzen ein hohes human- und ökotoxisches Potential. Ein Transfer dieser Schadstoffe in Pflanzen ist grundsätzlich möglich und auch unter Freilandbedingungen nachweisbar.In dieser Arbeit wurde eine Schadstoffanalyse des Rhizosphärenbodens — des unmittelbaren Einflußbereichs der Wurzel — vorgenommen, um die Wirkung von Pflanzen auf TNT-kontaminierte Böden näher zu charakterisieren. Als Versuchspflanzen dienten Buschbohnen (Phaseolus vulgaris).Für zwei unterschiedlich hoch belastete Freilandflächen konnte in den jeweiligen Rhizosphärenböden eine Abreicherung des extrahierbaren TNT um den Faktor 5 bis 6 nachgewiesen werden. In der Wurzel kam es demgegenüber auf der hoch belasteten Fläche zu einer Anreicherung von Nitroaromaten, wobei sich Aminodinitrotoluole als nachweisbare Hauptschadstoffe bestätigen ließen.Der Abreicherungsbefund verweist auf einen potentiellen Einsatz von Pflanzen im Rahmen der biologischen Sanierung rüstungsspezifisch belasteter Böden.AbstractMany sites of former ammunition plants are contaminated with the explosive 2,4,6-trinitrotoluene, its derivatives and reduction products. Such nitroaromatic compounds have a high human and ecotoxic potential. Plant uptake of these organic pollutants is known and could be confirmed under field conditions.In this paper rhizospheric soil was analyzed to characterize the effect of vegetation on TNT-contaminated soil. Common beans (Phaseolus vulgaris) were used as test plants. The experiments were performed on two areas with different TNT concentrations.The data reveal a significant decrease of extractable TNT in rhizospheric soil by a factor of 5 to 6 during the vegetation period. On the area with high TNT concentration, an enrichment of nitroaromatic compounds in root tissue was found compared to the rhizospheric soil. Aminodinitrotoluene could be confirmed as the primary pollutant in the root.These results refer to a potential application of plants to biological remediation of soil contaminated with ammunition-specific pollutants.

Degradation of wyerone, the phytoalexin of faba beans byRhizobium leguminosarum

Wyerone is the predominant phytoalexin produced byVicia faba. At a concentration of 100 µM, wyerone prolonged the lag phase before the onset of exponential growth of different strains ofRhizobium leguminosarum andBradyrhizobium japonicum. The response to wyerone was dose dependent, with a shorter lag phase occurring at lower concentrations. Wyerone was only moderately inhibitory towards the phytopathogenic bacteriumErwinia carotovora cv. atroseptica. HPLC analysis of the medium during bacterial growth indicated thatRhizobium leguminosarum was able to metabolize wyerone. The identification of the product as hydroxyester wyerol was confirmed by GC/MS analysis.

Low Concentrations of Phytoalexins Correlate with Resistance in Regenerated Plants from Meristem Cultures of Vicia faba L

Abstract In tissue cultures from shoot apex meristems with leaf primordias of Vicia faba cv. TP667, addition of low concentration of auxins (0.01 mg ・1-1) induced regeneration of whole plants at high frequency (100%). The combination of NAA and kinetin or GA , also induced a high yield of plant regeneration. Regenerated plants from various cultivars on a medium with 2 ,4 D (0.01 mg ・1-1) were infected with Botrytis cinerea, Phytophthora megasperma and R hizoctonia solani. Accumulation of phytoalexins, ethylene production and the resistance to fungal diseases were studied. In general, production of phytoalexins occurred at a high level in all cultivars infected with B. cinerea. Ethylene production varied more in the seven cultivars studied than phytoalexin accumulation. No cultivar was resistant to B. cinerea. The highest resistance and the low est concentration of phytoalexin was found after infection by R. solani, and phytoalexin accumulation and resistance were interm ediate in plants infected by P. megasperma. The data suggest that only low to medium concentrations of phytoalexin in faba beans are correlated with resistance of regenerated plants.

Wyerol and Wyerone Accumulation in Tissue Cultures of Vicia faba

Abstract Callus cultures of various cultivars of Vicia faba were studied for regeneration. During callus growth on agar or in liquid medium a black tissue was often observed correlated with an autolysis of some cells. With those tissues callus growth and regeneration of plants was inhibited. In black callus the phytoalexin synthesis is induced without infection by microorganism. The main phytoalexins in the callus tissue are wyerol and wyerone, with some wyeronic acid and dihydrowyerone. Wyerol was found especially in the cultivar Troy at a high concentration. In four cultivars the pooled phytoalexin concentration varied between 10 and 150 μg · g-1 fresh weight.