Record ID No. |
2013 |
Author(s) |
Shaw L.J., Hooker J.E , 2008 |
Affiliation |
University of Reading, Department of Soil Science, PO Box 233, Reading RG6 6DW, Berks, ENGLAND |
Title |
The fate and toxicity of the flavonoids naringenin and formononetin in soil |
Source. Vol.(no):Page |
Soil Biology & Biochemistry.40(2):528-536p. |
Categories |
Arbuscular Mycorrhiza |
Subjects |
Biochemistry |
Sub-subjects |
Miscellaneous |
Organism |
n.a. |
Country |
ENGLAND |
Abstracts |
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. |