Promotion of peroxidase activity in the cell wall of Nicotiana.

Peroxidase catalyzes the oxidation of indole-3-acetic acid. The primary products of this reaction stimulate growth in plants. Therefore, our concept is that an increase in peroxidase activity will increase the effect of indole-3-acetic acid as a growth hormone. Our objective was to study the effect of 2,3,5-triiodobenzoic acid, a growth regulator, on isoperoxidases in the cell wall and cytoplasm of Nicotiana. Isoperoxidases from the cell wall and cytoplasmic fractions were separated by acrylamide gel electrophoresis. We found that 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase peroxidase activity in the cell wall. Since both 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase the activity of the same isoperoxidase, we conclude that 2,3,5-triiodobenzoic acid synergizes rather than antagonizes auxin action, and we suggest that this increase in indole-3-acetic acid oxidase activity sensitizes plant tissues to auxin.