SALT TOLERANCE IN THE HALOPHYTE SUAEDA MARITIMA (L.) DUM.

THE EFFECT OF SALINITY ON THE CONCENTRATION OF SODIUM IN THE XYLEM

Authors

  • N. J. W. CLIPSON,

    1. School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG
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    • *

      Plant Breeding Institute, Maris Lane, Trumpington, Cambrige, CB2 2LQ.

  • T. J. FLOWERS

    Corresponding author
    1. School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG
      †To whom requests for reprints should be directed
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†To whom requests for reprints should be directed

Summary

Rates of ion transport and transpiration were measured during the day and night in whole seedlings of Suaeda maritima growing over a range of salinities, in order to calculate concentrations of sodium and potassium in the xylem during these periods. Mean sodium concentration in the xylem was maximal at 56 mol m−3 Na with an external salinity of 200 mol m−3 NaCl. The sodium concentration in the xylem was greater in the dark than in the light at all external salinities investigated. Comparison of the external sodium with that in the xylem indicated that sodium was more strongly excluded from the transpiration stream as salinity increased. The mean concentration of potassium in the xylem declined as external NaCl concentration increased, although selectivity for potassium increased at higher salinities. Results are discussed in relation to osmotic adjustment in S. maritima.

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