Auxin Physiology in Bean Leaf Stalks.

Abstract

Auxin production was found in excised bean (Phaseolus vulgar is. var. Black Valentine) leaf stalks when immersed in water. Auxin disappeared from excised bean leaf stalks when they were kept in moist air. The low auxin concentrations found in previous Avena assays of bean leaf stalks appear to be real; no evidence was found of inhibitors modifying the response of Avena coleoptile. IAA transport through sections of bean leaf stalks was not obtained, although IAA disappeared from agar blocks in contact with leaf stalk sections. The disappearance was apparently due to the diffusion of IAA into the sections and its inactivation there. Evidence of an IAA inactivating system in bean leaf stalks was obtained. The system appears to be composed of at least two parts. In the first part there is an oxidative, enzymatic production of an IAA inactivator which is thermostable. In the second part there is a reaction of the inactivator and IAA to form a product which is inactive in the Avena assay. The product is negative to the ferric chloride test (for IAA) but is positive to the Hopkins-Cole test (for indole).