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Studies on the mucilaginous layer of barley (Hordeum vulgare) roots

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Abstract

The nature and composition of the external, mucilageneous layer of barley roots was studied by extraction methods and electron microscopy.

Barley roots were extracted with chloramphenicol-supplemented water at 35°C, with NH4Cl at various concentrations and with pectinase solutions. The kinetics of transfer of bacteria, total and reducing sugars, proteins, Ca++ and K+ was studied, and the removal of the mucigel from the extracted roots was followed under the electron microscope.

Within 2 to 3 hours of treatment with water, the rate of release of sugars, ions, proteinaceous material and bacteria, was reduced to almost zero. Increasing concentrations of ammonium chloride enhanced transfer of ions to the extracting solution but affected sugar extraction to a lesser extent. Electron micrographs of ammonium chloride-extracted roots revealed that the amorphous, rather than the fibrillar fraction of the mucigel was removed. At 103 meq of NH4Cl, distortion of the epidermal layer of the extracted roots was observed. With pectinase as an extractant, there was some enhancement of sugars and ions transfer from the roots to the extracting solution. Electron micrographs showed that the main site of extraction of pectinase was the boundary layer between the root surface and the mucigel. Paper chromatography of the acid hydrolyzate of the water extracted, ethanol-precipitated fraction showed the presence of compounds identical in Rf values to D-glucose, D-arabinose, D-glucuronic acid and D-galacturonic acid. Present methods available for the extraction of the mucigel do not allow the differentiation between extracted pectic compounds which originate from the internal root tissue, and the mucigel. re]19751128

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Authors and Affiliations

  1. The Hebrew University, P.O.B. 12, 76100, Rehovot, Israel

    E. Dayan, A. Banin & Y. Henis

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  1. E. Dayan
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  2. A. Banin
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  3. Y. Henis
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Dept. of Field Crops

Dept. of Soil and Water Sciences

Dept. of Microbiology and Phytopathology

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Dayan, E., Banin, A. & Henis, Y. Studies on the mucilaginous layer of barley (Hordeum vulgare) roots. Plant Soil 47, 171–191 (1977). https://doi.org/10.1007/BF00010378

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