Independence of morphactin and gibberellin effects upon higher plants.

Two fltnorene-9-carboxylic acid derivatives (fig 1, I and II) have recently been shown to be potent growth regulators in higher plants (1), and have been givein the trivial name, morphactins. The structtural similarity between the morphactins and gibberellic acid (fig 1, III) immediately suggested a common site of action. In fact, Ziegler, et al. (4) have claimed that methyl-morphactin (I) is a competitive inhibitor of the action of gibberellin; they also showed that methyl morphactin did not inhibit biosynthesis of gibberellin by Fusarium oxyformtis. Their data with regard to a competitive relationship between gibberellin and morphactin was obtained only from measturements of pea seedling height. This data can be interpreted in other ways than by asstuming a common receptor site for the 2 compoutnds.