Mesurement of longitudinal ion profiles in single roots of Hordeum and Atriplex by use of flameless atomic absorption spectroscopy

Summary A method is described by which the Na⁺ and K⁺ content in 0.5 mm sections of single roots of Hordeum distichon L. and Atriplex hortensis L. can be determined by use of flameless atomic absorption spectroscopy. By this method the longitudinal profiles of K⁺ and Na⁺ along low salt roots and roots which had been equilibrated with or grown in K⁺-free 1 mM Na⁺-solution were determined. The profiles reveal that high K⁺/Na⁺ ratios in the cytoplasm are maintained also in K⁺-free solutions. In solutions containing 1 mM Na⁺ a high K⁺/Na⁺ selectivity was found to be dependent on sufficient aeration. From the ion profiles the cytoplasmic (110 mM) and vacuolar (20 mM) K⁺ concentration in low salt barley roots—values which are unobtainable by compartmental analysis—could be estimated.