ABSTRACT
The mechanism of auxin protection by auxin protector-I (Pr-I) of the Japanese morning glory was studied in vitro. Four lines of evidence indicate that Pr-I acts as a strong reductant which prevents the peroxidase-catalyzed oxidation of IAA: 1) The kinetics of the reaction are best explained on this basis. 2) The Pr-I-induced lag preceding auxin destruction by peroxidase is completely eliminated by a strong oxidant such as H(2)O(2) at a concentration which does not appreciably affect the reaction rate. 3) Strong organic reductants mimic the Pr-I-induced lag. And 4) when the reaction rate is altered by varying the concentrations of the reactants, or the temperature, the length of the Pr-I-induced lag varies inversely with the reaction rate.
ABSTRACT
Auxin protector-I of the Japanese morning glory is inactivated by manganese. Experiments carried out in vitro indicate that in the absence of oxygen the manganic, but not the manganous, ion rapidly inactivates the protector. It is clear from these, and other data described in this report, and the results of other workers, that in the presence of oxygen, manganese accelerates auxin inactivation by means of 2 separate and distinct mechanisms: 1) manganese catalyzes the oxidation of auxin protectors, and 2) following the inactivation of the protectors, or in the absence of protectors, accelerates the oxidation of indoleacetic acid by endogenous peroxidases.
