Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 525518
Title Zoutophoping door plantenwortels : een physisch-chemische studie over het binnentreden en de verplaatsing van ionen in een ruimte met een amphoteer kolloid
Author(s) Vervelde, G.J.
Source University. Promotor(en): H.J.C. Tendeloo. - Wageningen : Veenman - 90
Publication type Dissertation, internally prepared
Publication year 1952
Keyword(s) kunstmeststoffen - absorptie - plantenvoeding - voedingsstoffen - vloeistoffen (liquids) - wortels - worteldruk - zuiging - fertilizers - absorption - plant nutrition - nutrients - liquids - roots - root pressure - suction
Categories Plant Nutrition Physiology / Fertilizers, Fertilizer Application
Abstract 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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