Union Catalogue of Agricultural Libraries in the Netherlands
The WUR Library Catalogue contains bibliographic data on books and periodicals held by the libraries of Wageningen University and Research Centre and some 15 associated libraries. Holding data are added to each record.
Subjects covered include Agrotechnology, Food and Food Production, Plant and Animal Sciences, Soil Science, Geo-information, Landscape and Spatial Planning, Water and Climate, Ecosystem Studies, Economics and Society.
The joint collections of the participating libraries cover a substantial part of the internationally available scientific literature in these disciplines.
As far as Dutch scientific literature in these fields is concerned, coverage can be considered near 100%, including much of the so-called "grey literature".
All titles are entered in their original language. Keywords are added to facilitate subject searching.
The database is updated every day and now contains over 830.000 records.
A Donnan relation between the medium and the outermost layer of the root or cell contents was supposed. Measurement of membrane potentials, indicating an unequal distribution of ions across the root wall, was the only practical way of showing its existence. Measurements of root potential in solutions of a broad pH range revealed the amphoteric nature of the root contents. The concentration of cell- bound (colloidal) ions, is the difference between the dissociated fractions of acid groups and of basic groups. This surplus varies with pH. If the constants K 1 and K 2 (concentration of cell-bound ions = K 1 log c H+ + K 2 ) are estimated, the concentration of fixed ions can be calculated for any pH. The adsorption capacities thus calculated with the prevailing pH values better approach the mineral contents in plant material than LUNDEG+RDH'S conclusion that a strongly acid component is present. The function of c H+ gradients in salt transport in an amphoteric system is also considered. Maximum accumulation of anions And cations takes place near the iso-electric pH. Three stages in the accumulation processes are distinguished: formation of organic acids in young tissue; accumulation of mineral anions from the medium; decrease of acidity, causing cation absorption and salt accumulation.
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