Studies on Auxin Protectors. IV. The Effect of Manganese on Auxin Protector-I of the Japanese Morning Glory.

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.