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A mathematical analysis of water and solute transport across the root of Ricinus communis

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Summary

A mathematical analysis of the relationship between the flux of water, f H2O, and the flux of potassium f K, to the xylem of exuding root systems of Ricinus communis, is presented. Previous analyses (Baker and Weatherley, 1969; Minchin and Baker, 1969) have indicated the presence of a water dependent and a water independent f K both of which vary with the external concentration of potassium, Cm, supplied as potassium nitrate.

The present analysis reveals that whereas at Cm values<1 mM both components of f K contribute ions to the osmotically active solutions within the osmotic barrier, at Cm values>1 mM only the water dependent f K is responsible for the osmotic work. This suggests that the ions are released within different regions of the stele. It is proposed that at cm values<1 mM both components are released from the inner stelar tissues whilst at higher Cm values the water dependent f K is released from the outer stelar tissues. This requires that the solute permeability of the plasmalemma of the outer stelar tissues increases markedly at or about Cm values of 1 mM.

It is postulated that the required separation of the two f K components within the stelar symplasm at Cm values>1 mM is due to the water independent f K being in a bound state, possibly being transported along a chain of binding sites whilst the water dependent f K is in a free state within the aqueous phase of the cytoplasm.

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Authors and Affiliations

  1. School of Biology, Leicester Polytechnic, Leicester, UK

    F. R. Minchin

  2. School of Biological Sciences, University of Sussex, Sussex, UK

    D. A. Baker

Authors
  1. F. R. Minchin
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  2. D. A. Baker
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Minchin, F.R., Baker, D.A. A mathematical analysis of water and solute transport across the root of Ricinus communis . Planta 94, 16–26 (1970). https://doi.org/10.1007/BF00386605

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  • DOI: https://doi.org/10.1007/BF00386605

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