The Relationship of Magnesium Ion and Molecular Structure to 2,4-Dichlorophenoxyacetic Acid and Some Related Compounds to the Inhibition of the Respiration of Azotobacter vinelandii.

Abstract

The in-hibition of oxygen uptake by A. vinelandii in the presence of 2,4-dichioro-phenoxyacetlc, p-chlorophenoxyacetlc, o-chlorophenoxyacetic, phenyl-propionic and phenoxyacetic acids has been studied. The role of Mg in alleviating the toxicity of the acids has been found to vary with the compound used. At a concentration of 9.2 x 10-3 [image] only 2,4-D completely inhibited the respiration of A. vinelandii. Phenoxyacetic acid, phenyl-propionic acid, o- and p-chlorophenoxyacetic acids, inhibited the test organism to lesser degrees. Protection from the inhibition produced by 2 x 10-2 [image] phenoxyacetic acid and phenylpropionic acid was afforded by molar ratios of 1:1 and 2:1, respectively, Mg to the agents. Considerable protection, though not complete protection, from the inhibition produced by 2 x 10-2 [image] o-chlorophenoxyacetic acid was provided by a molar ratio of 2:1, Mg to the test compound. A 1:1 molar ratio of Mg to the agent provided protection from the inhibition produced by p-chlorophenoxyacetic acid at 8 x 10-3 [image].