Calcium Requirement for Indoleacetic Acid-induced Acidification by Avena Coleoptiles

摘要

The ionic specificity of IAA-induced acidification by Avena coleoptiles was studied, using zwitterionic, presumably impermeant buffers. The acidification was almost totally dependent on divalent cations with an order of effectiveness of Ca²⁺ ≥ Sr²⁺ > Mn²⁺, Mg²⁺; whereas other polyvalent cations tested were ineffective. The Ca²⁺ response was IAA-dependent. The CaCl2 concentration was optimal at 0.3 to 1 mm and inhibitory at higher concentrations. Sr²⁺ inhibited Ca²⁺-dependent acidification and monovalent cations such as K⁺ did not induce additional acidification in the presence of optimal CaCl2. These data are consistent with a mechanism for IAA-induced acidification involving a Ca²⁺ −H⁺ exchange.