Auxin and gibberellin interactions in morphogenesis

Summary The effect of gibberellic acid on the biosynthesis of diphenolic compounds, growth and root initiation was investigated to determine a possible relationship between the development of morphological structures and a biochemical process. The results indicated that the effect of GA on growth was due to an increase in the amount of auxin-like substances.The mechanism by which a higher auxin level was brought about through treatment with gibberellin was shown not to involve inhibitors of IAA-oxidase but the synthesis of auxin. The level of anthocyanin and hydronaphtoquinone, which should be expected to inhibit IAA oxidation, does not affect the level of endogenous auxin-like substances. In contrast to a previous paper, it cannot be concluded that the rooting ability of balsam cuttings is determined by the level of indoleacetic acid.