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Electrophysiological characterization of pathways for K + uptake into growing and non‐growing leaf cells of barley
Author(s) -
VOLKOV VADIM,
BOSCARI ALEXANDRE,
CLÉMENT MATHILDE,
MILLER ANTHONY J.,
AMTMANN ANNA,
FRICKE WIELAND
Publication year - 2009
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.02034.x
Subject(s) - apoplast , elongation , hordeum vulgare , biophysics , ion transporter , ion channel , patch clamp , epidermis (zoology) , membrane potential , potassium , chemistry , electrophysiology , potassium channel , biology , botany , membrane , biochemistry , anatomy , cell wall , poaceae , materials science , neuroscience , receptor , organic chemistry , metallurgy , ultimate tensile strength
Potassium is a major osmolyte used by plant cells. The accumulation rates of K + in cells may limit the rate of expansion. In the present study, we investigated the involvement of ion channels in K + uptake using patch clamp technique. Ion currents were quantified in protoplasts of the elongation and emerged blade zone of the developing leaf 3 of barley ( Hordeum vulgare L.). A time‐dependent inward‐rectifying K + ‐selective current was observed almost exclusively in elongation zone protoplasts. The current showed characteristics typical of Shaker‐type channels. Instantaneous inward current was highest in the epidermis of the emerged blade and selective for Na + over K + . Selectivity disappeared, and currents decreased or remained the same, depending on tissue, in response to salt treatment. Net accumulation rates of K + in cells calculated from patch clamp current–voltage curves exceeded rates calculated from membrane potential and K + concentrations of cells measured in planta by factor 2.5–2.7 at physiological apoplastic K + concentrations (10–100 m m ). It is concluded that under these conditions, K + accumulation in growing barley leaf cells is not limited by transport properties of cells. Under saline conditions, down‐regulation of voltage‐independent channels may reduce the capacity for growth‐related K + accumulation.