Inhibition of Ion Absorption and Respiration in Barley Roots.

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Abstract
Pre-treatment of excised roots of barley seedlings with K salts of fluoride, iodoacetate, transaconitate, fluoroacetate and malonate inhibited subsequent K and Br absorption equally at less than the 50% level of inhibition, but inhibited K absorption to a greater extent above this level. K arsenite inhibited the absorption of Br slightly more than that of K at all levels of inhibition. K cyanide inhibited Br absorption more than K absorption at the 50% level of inhibition, but inhibited both equally at the 75% level. K arsenate inhibited the absorption of both ions equally. 2, 4-Dinitrophenol and carbon monoxide, in the dark, inhibited the concomitant absorption of K more than that of Br. In all cases, except 95% carbon monoxide in the light, respiration was depressed less than ion absorption. Various Krebs cycle acids were effective in overcoming fluoride and fluoroacetate inhibition. Malonate inhibition was enhanced by succinate but overcome by malate. It is postulated that separate but parallel mechanisms exist for the absorption of K and Br. The roles of phosphorylation and oxidative metabolism in ion absorption are discussed.

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