A new perfusion system for the measurement and characterization of potential rates of soil nitrification |
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Authors: | K Killham |
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Institution: | (1) Laboratoire de Pathologie Végétale, Université P. et M. Curie (Paris VI), Tour 53, 4 place Jussieu, F-75252 Paris Cedex 05, France;(2) Laboratoire de Biologie micromoléculaire et Phytochimie, Université de Lyon I., 43 Bd, du 11 Novembre 1918, F-69622 Villeurbanne Cedex, France |
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Abstract: | The effect of two isoflavonoids, coumestrol and daidzein which are present in aseptically grown roots and root exudates of
soybean, was tested on some rhizospheric microorganisms. It was found that coumestrol promotes the growth ofR. japonicum USDA 138 (about 30%) andR. leguminosarum (about 15%) whereas it inhibits the growth ofAgrobacterium tumefaciens (about 50%) andPseudomonas sp. (about 20%). The following microorganisms were unaffected by this molecule:R. japonicum W505,Agrobacterium radiobacter, Micrococcus luteus andCryptococcus laurentii. It was found that daidzein promotesR. japonicum USDA 138 growth (about 20%) and inhibitsPseudomonas sp. growth (about 20%); other microorganisms were unaffected. In addition, coumestrol favoured the formation of ‘coccoids’
cells byRhizobium japonicum USDA 138 which could be the infective state of this strain. It seems that this compound is able to help nodulation of soybean
by aRhizobium strain. This result supports the work of Peterset al. (1986) and Redmondet al. (1986) who show that flavones present in plant exudates induces expression of nodulation genes in Rhizobium. |
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Keywords: | bacterial growth coumestrol daidzein Glycine max isoflavonoids rhizobia rhizospheric microorganisms soybean |
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