THE INDEPENDENT ACTION OF MORPHACTINS AND GIBBERELLIC ACID ON HIGHER PLANTS1

Abstract

The comparative activity of three morphactins, n-butyl-9-hydroxy fluorene-9-carboxylate (IT 3233), 9-hydroxy-fluorene-9-carboxylic acid (IT 3235) and methyl-2-chloro-9-hydroxy fluorene-9-carboxylate (IT 3456) on the action of gibberellic acid (GA₃) were examined utilizing dwarf pea (Progress No. 9), dwarf corn (strain d-5), CCC dwarfed Alaska pea, and embryoless barley half-seeds. When applied either prior to or simultaneously with GA₃ the morphactins were without effect in reducing the response of the dwarf peas to the gibberellin. In fact IT 3233 and IT 3235 in combination with GA₃ produced taller plants than the GA₃ controls. Similar results were observed using CCC dwarfed Alaska peas. The morphactins did, however, produce several morphological effects on the peas. In addition, they were effective in breaking apical dominance in the peas. The morphactins were also without effect on the dwarf corn bioassay and no morphological changes were observed. In the embryoless barley half-seeds the morphactins did not inhibit the response of the tissue to the GA₃. Also, the morphactins did not exhibit gibberellin-like properties. The results suggest that morphactins do not compete with gibberellin for similar sites of action.