Ionic and osmotic relations in quinoa (Chenopodium quinoa Willd.) plants grown at various salinity level

Yuda Hariadi, Karl Marandon, Yu Tian, Sven-Erik Jacobsen, Sergey Shahala

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    Abstract

    Ionic and osmotic relations in quinoa (Chenopodium quinoa Willd.) were studied by exposing plants to six salinity
    levels (0–500 mM NaCl range) for 70 d. Salt stress was administered either by pre-mixing of the calculated amount of
    NaCl with the potting mix before seeds were planted or by the gradual increase of NaCl levels in the irrigation water.
    For both methods, the optimal plant growth and biomass was achieved between 100 mM and 200 mM NaCl,
    suggesting that quinoa possess a very efficient system to adjust osmotically for abrupt increases in NaCl stress. Up
    to 95% of osmotic adjustment in old leaves and between 80% and 85% of osmotic adjustment in young leaves was
    achieved by means of accumulation of inorganic ions (Na+, K+, and Cl–) at these NaCl levels, whilst the contribution
    of organic osmolytes was very limited. Consistently higher K+ and lower Na+ levels were found in young, as
    compared with old leaves, for all salinity treatments. The shoot sap K+ progressively increased with increased
    salinity in old leaves; this is interpreted as evidence for the important role of free K+ in leaf osmotic adjustment under
    saline conditions. A 5-fold increase in salinity level (from 100 mM to 500 mM) resulted in only a 50% increase in the
    sap Na+ content, suggesting either a very strict control of xylem Na+ loading or an efficient Na+ removal from leaves.
    A very strong correlation between NaCl-induced K+ and H+ fluxes was observed in quinoa root, suggesting that
    a rapid NaCl-induced activation of H+-ATPase is needed to restore otherwise depolarized membrane potential and
    prevent further K+ leak from the cytosol. Taken together, this work emphasizes the role of inorganic ions for osmotic
    adjustment in halophytes and calls for more in-depth studies of the mechanisms of vacuolar Na+ sequestration,
    control of Na+ and K+ xylem loading, and their transport to the shoot.
    OriginalsprogEngelsk
    TidsskriftJournal of Experimental Botany
    Vol/bind62
    Udgave nummer1
    Sider (fra-til)185-193
    Antal sider9
    ISSN0022-0957
    DOI
    StatusUdgivet - 2011

    Emneord

    • BRIC
    • Halophyte
    • Ion loading
    • Membrane transport
    • Osmotic adjustment
    • Potassium,
    • Salt stress
    • Sequestration
    • Sodium

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