REGULATION OF K+ INFLUX IN EXCISED BARLEY ROOTS - RELATIONSHIPS BETWEEN K+ INFLUX AND ELECTROCHEMICAL POTENTIAL DIFFERENCES

The electrochemical potential differences {Mathematical expression} for potassium, between excised barley (Hordeum vulgare L.) roots and external media containing 0.05 mM KCl+0.5 mM CaSO4, were determined over a 4-h period during which initially low-K+ roots accumulated K+ by pretreatment in 50 mM KCl plus 0.5 mM CaCl2. This pretreatment resulted in increased internal [K+], decreased K+ influx (as measured from 0.05 mM KCl+0.5 mM CaSO4) and decreased values of {Mathematical expression}. These observations indicate that the decline of K+ influx associated with increased internal K+ concentration cannot be accounted for by passive adjustment to the electrochemical gradient for this ion. © 1979 Springer-Verlag.