The Effect of Indole-3-Acetic Acid in the Diastase Charcoal Model System.

A mechanism of auxin action was proposed by EYSTER (3, 4) similar to the classical adsorption theory of narcotic action of TRAUBE and WARBURG (2). It was based on the action of synthetic auxins in a model system composed of charcoal as a representative colloid, and diastase and starch as representative plant enzyme and substrate. Recent evidence (1, 5, 6, 7) that starch mobilization is one of the characteristic responses to auxin stimulation makes this proposal of increased interest and its substantiation even more urgent. EYSTER'S experiments are subject to several criticisms which are considered later, but his proposal is worthy of further examination. His conclusions were that auxins have two types of action in the model system, and presumably also in plant tissues: ". . . phase I, release of enzyme in whole or in part from charcoal; and phase II, effect on enzyme action proper" (4). He argued that in "phase I" the release of diastase or other enzyme from the inactive bound condition by auxins was the cause of growth-promoting effects and that in "phase II" inactivation of free diastase or other enzyme was the cause of growth-inhibiting effects. The object of the present work was to reinvestigate EYSTER'S observations on the diastase-charcoal model system using somewhat different and more rigorous experimental conditions. The effect of three types of interactions of auxin, charcoal, diastase, and starch on diastatic activity was investigated: (1) auxin on free diastase, (2) competitive adsorption of auxin and diastase on charcoal, and (3) the interaction of all four components. Methods and materials