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  • 1
    ISSN: 1573-1561
    Keywords: Wheat ; Triticum aestivum ; soybean ; Glycine max ; no till ; conventional till ; soil extracts ; allelopathy ; phenolic acids ; Folin & Ciocalteu's phenol reagent ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Soil core (0–2.5 and/or 0–10 cm) samples were taken from wheat no till, wheat-conventional till, and fallow-conventional till soybean cropping systems from July to October of 1989 and extracted with water in an autoclave. The soil extracts were analyzed for seven common phenolic acids (p-coumaric, vanillic,p-hydroxybenzoic, syringic, caffeic, ferulic, and sinapic; in order of importance) by high-performance liquid chromatography. The highest concentration observed was 4 μg/g soil forp-coumaric acid. Folin & Ciocalteu's phenol reagent was used to determine total phenolic acid content. Total phenolic acid content of 0- to 2.5-cm core samples was approximately 34% higher than that of the 0- to 10-cm core samples. Phenolic acid content of 0- to 2.5-cm core samples from wheat-no till systems was significantly higher than those from all other cropping systems. Individual phenolic acids and total phenolic acid content of soils were highly correlated. The last two observations were confirmed by principal component analysis. The concentrations were confirmed by principal component analysis, tions of individual phenolic acids extracted from soil samples were related to soil pH, water content of soil samples, total soil carbon, and total soil nitrogen. Indirect evidence suggested that phenolic acids recovered by the water-autoclave procedure used came primarily from bound forms in the soil samples.
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  • 2
    ISSN: 1573-1561
    Keywords: EDTA extraction ; water extraction ; NaOH extractions ; Cecil soil ; ferulic acid ; p-coumaric acid ; p-hydroxybenzoic acid ; vanillic acid ; sorption ; free phenolic acids ; reversibly bound phenolic acids ; allelopathy ; soil microbial ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Sterile and microbe reinfested Cecil Ap and Bt soil materials amended with 0 to 5 µmol/g of ferulic acid,p-coumaric acid,p-hydroxybenzoic acid, or vanillic acid were extracted after varying time intervals with water, EDTA, or NaOH to characterize sorption of cinnamic and benzoic acid derivatives and to determine the effectiveness of water and EDTA extractions in estimating concentrations of free and reversibly bound phenolic acids in soils. Basic EDTA (0.5 M, pH 8) extractions and water extractions provided good estimates of both free and reversibly bound cinnamic acid derivatives, but not of benzoic acid derivatives. Neutral EDTA (0.25 M, pH 7) and water extractions, however, were effective for both cinnamic and benzoic acid derivatives Rapid initial sorption of both cinnamic and benzoic acid derivatives was followed by slow long-term sorption of the cinnamic acid derivatives. Slow long-term sorption was not observed for the benzoic acid derivatives. The amount of sorption of phenolic acids in soil materials was directly related to the concentration of phenolic acids added to soil materials. The addition of a second phenolic acid to the soil materials did not substantially affect the sorption of each individual phenolic acid. Sodium hydroxide extractions, which were made only after phenolic acids in phenolic acid-amended and non-amended soil material were depleted by microbes, confirmed that neutral EDTA and water extractions of soils can be used to make accurate estimates of baseline (residual) levels of free and reversibly bound phenolic acids available to soil microbes and, thus, potentially to seeds and roots.
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  • 3
    ISSN: 1573-1561
    Keywords: Cover crops ; wheat ; Triticum aestivum ; soybean ; Glycine max ; soil extracts ; germination bioassays ; phenolic acids ; hydroxamic acids ; allelopathy ; slope analysis ; ivy-leaved morning glory ; Ipomoea hederacea ; crimson clover ; Trifolium incarnalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The primary objective of this research was to determine if soil extracts could be used directly in bioassays for the detection of allelopathic activity. Here we describe: (1) a way to estimate levels of allelopathic compounds in soil; (2) how pH, solute potential, and/or ion content of extracts may modify the action of allelopathic compounds on germination and radicle and hypocotyl length of crimson clover (Trifolium incarnatum L.) and ivyleaved morning glory (Ipomoea hederacea L. Jacquin.); and (3) how biological activity of soil extracts may be determined. A water-autoclave extraction procedure was chosen over the immediate-water and 5-hr EDTA extraction procedures, because the autoclave procedure was effective in extracting solution and reversibly bound ferulic acid as well as phenolic acids from wheat debris. The resulting soil extracts were used directly in germination bioassays. A mixture of phenolic acids similar to that obtained from wheat-no-till soils did not affect germination of clover or morning glory and radicle and hypocotyl length of morning glory. The mixture did, however, reduce radicle and hypocotyl length of clover. Individual phenolic acids also did not inhibit germination, but did reduce radicle and hypocotyl length of both species. 6-MBOA (6-methoxy-2,3-benzoxazolinone), a conversion product of 2-o-glucosyl-7-methoxy-1,4-benzoxazin-3-one, a hydroxamic acid in living wheat plants, inhibited germination and radicle and hypocotyl length of clover and morning glory. 6-MBOA, however, was not detected in wheat debris, stubble, or soil extracts. Total phenolic acids (FC) in extracts were determined with Folin and Ciocalteu's phenol reagent. Levels of FC in wheat-conventionaltill soil extracts were not related to germination or radicle and hypocotyl length of either species. Levels of FC in wheat-no-till soil extracts were also not related to germination of clover or morning glory, but were inversely related to radicle and hypocotyl length of clover and morning glory. FC values, solute potential, and acidity of wheat-no-till soil extracts appeared to be independent (additive) in action on clover radicle and hypocotyl length. Radicle and hypocotyl length of clover was inversely related to increasing FC and solute potential and directly related to decreasing acidity. Biological activity of extracts was determined best from slopes of radicle and hypocotyl length obtained from bioassays of extract dilutions. Thus, data derived from the water-autoclave extraction procedure, FC analysis, and slope analysis for extract activity in conjunction with data on extract pH and solute potential can be used to estimate allelopathic activity of wheat-no-till soils
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