Water extractable humic substances

Figure 1 Proposed role of humic substances on iron nutrition of plants possessing dif fereni strategies for iron acquisition. WEHS, water-extractable humic substances, as described in the text.

S. Cesco, V. Rdmheld, Z. Varanini, and R. Pinton, Solubilization of iron by a water extractable humic substances fraction. J. Plant Nutr. Soil Sci. 763 285 (2000). 

R. Pinton, S. Cesco, S. Santi, F. Agnolon, and Z. Varanini, Water-extractable humic substances enhance iron deficiency responses by Fe-deficient cucumber plants. Plant Soil 2/0 145 (1999). 

R. (2000) Solubilization of iron by water-extractable humic substances. J. Plant Nutr. SoilSd. 163 285-290 Chabaux, F. Cohen, A.S. O Nions, R.K. ... 

Also, Schmidt et al. (2005) found a significant increase in root hair density by working with Arabidopsis thaliana, which were treated with water extractable humic substances (WEHS), suggesting that these substances induce a nutrient acquisition response that favors the uptake of nutrients via an increase in the absorptive surface area. Furthermore, a phenotypical analysis of an array of mutants harbouring defects in root epidermal patterning revealed that root hair density of the ttg and gl2 mutants, defective in cell specification, was significantly modified, indicating an effect at/or downstream of the determination of the cells. 

Pinton, R., Cesco, S., Iacoletti, G, Astolfi, S., and Varanini, Z. (1999a). Modulation of NO3 uptake by water-extractable humic substances Involvement of root plasma membrane H+ATPase. Plant Soil 215,155-161. 

Schmidt, W., Santi, S., Pinton, R., and Varanini, Z. (2007). Water-extractable humic substances alter root development and epidermal cell pattern in Arabidopsis. Plant Soil 300,... 

Supercritical fluid extraction (SFE) is generally used for the extraction of selected analytes from solid sample matrices, but applications have been reported for aqueous samples. In one study, recoveries of 87-100% were obtained for simazine, propazine, and trietazine at the 0.05 ug mL concentration level using methanol-modified CO2 (10%, v/v) to extract the analytes, previously preconcentrated on a C-18 Empore extraction disk. The analysis was performed using LC/UV detection. Freeze-dried water samples were subjected to SFE for atrazine and simazine, and the optimum recoveries were obtained using the mildest conditions studied (50 °C, 20 MPa, and 30 mL of CO2). In some cases when using LEE and LC analysis, co-extracted humic substances created interference for the more polar metabolites when compared with SFE for the preparation of the same water sample. ... 

The high production volume chemical, 4-chloro-2-methylphenol, XVI was photolysed in distilled and natural waters and aqueous solutions of soil-extracted humic substances (Ranker, Spain) under various irradiation conditions with monochromatic light at 280 nm, using polychromatic lamps emitting between 300 and 450 nm, and in natural sunlight (June, Clermont-Ferrand, France) [78,79]. 

Soil extracts are usually very complex. In water samples, humic and fulvic acids make analysis difficult, especially when polar substances are to be determined. Multidimensional chromatography can also make a significant contribution here to this type of analysis. 

Extractable concentrations of sediment-bound zinc were positively correlated with zinc concentrations in deposit feeding clams (Luoma and Bryan 1979). Availability of sediment zinc to bivalve molluscs was higher at increased sediment concentrations of amorphous inorganic oxides or humic substances, and lower at increased concentrations of organic carbon and ammonium acetate-soluble manganese. Zinc uptake by euryhaline organisms was enhanced at low water salinity (Luoma and Bryan 1979). 

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