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The fate and toxicity of the flavonoids naringenin and formononetin in soil

Shaw, L.J. and Hooker, J. E. (2008) The fate and toxicity of the flavonoids naringenin and formononetin in soil. Soil Biology & Biochemistry, 40 (2). pp. 528-536. ISSN 0038-0717

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To link to this article DOI: 10.1016/j.soilbio.2007.09.021

Abstract/Summary

The flavonoid class of plant secondary metabolites play a multifunctional role in below-ground plant-microbe interactions with their best known function as signals in the nitrogen fixing legume-rhizobia symbiosis. Flavonoids enter rhizosphere soil as a result of root exudation and senescence but little is known about their subsequent fate or impacts on microbial activity. Therefore, the present study examined the sorptive behaviour, biodegradation and impact on dehydrogenase activity (as determined by iodonitrotetrazolium chloride reduction) of the flavonoids naringenin and formononetin in soil. Organic carbon normalised partition coefficients, log K-oc, of 3.12 (formononetin) and 3.19 (naringenin) were estimated from sorption isotherms and, after comparison with literature log K-oc values for compounds whose soil behaviour is better characterised, the test flavonoids were deemed to be moderately sorbed. Naringenin (spiked at 50 mu g g(-1)) was biodegraded without a detectable lag phase with concentrations reduced to 0.13 +/- 0.01 mu g g(-1) at the end of the 96 h time course. Biodegradation of formononetin proceeded after a lag phase of similar to 24 with concentrations reduced to 4.5 +/- 1% of the sterile control after 72 h. Most probable number (MPN) analysis revealed that prior to the addition of flavonoids, the soil contained 5.4 x 10(6) MPNg(-1) (naringenin) and 7.9 x 10(5) MPNg(-1) (formononetin) catabolic microbes. Formononetin concentration had no significant (p > 0.05) effect on soil dehydrogenase activity, whereas naringenin concentration had an overall but non-systematic impact (p = 0.045). These results are discussed with reference to likely total and bioavailable concentrations of flavonoids experienced by microbes in the rhizosphere. (c) 2007 Elsevier Ltd. All rights reserved.

Item Type:Article
Divisions:Faculty of Science > School of Archaeology, Geography and Environmental Science > Department of Geography and Environmental Science
Faculty of Science > School of Archaeology, Geography and Environmental Science
Faculty of Science > School of Archaeology, Geography and Environmental Science > Earth Systems Science
Interdisciplinary centres and themes > Soil Research Centre
ID Code:4091
Uncontrolled Keywords:flavonoids plant secondary metabolites rhizosphere biodegradation toxicity sorption POLYCYCLIC AROMATIC-HYDROCARBONS ARBUSCULAR MYCORRHIZAL FUNGUS GENE-INDUCING FLAVONOIDS ANTIFUNGAL ACTIVITY RHIZOBIUM SORPTION ISOFLAVONOIDS ROOTS PATHWAY COLONIZATION
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