Changes in Assimilated C Distribution and Soluble Acid Invertase Activity of Zinnia elegans Induced by Uniconazol, an Inhibitor of Gibberellin Biosynthesis.

The physiological aspects involved in the Uniconazol-induced morphological changes in Zinnia elegans Jacq. cv Red Sun were clarified biochemically by determining the distribution of assimilated (13)C as well as the soluble acid invertase activity. The application of Uniconazol, (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-pentane-3-ol, reduced the growth of stems and leaves without affecting the roots. In addition, the translocation of assimilated (13)C from leaf to other organs was inhibited, with the stem being more restricted than the root. These changes were matched by a corresponding decrease in the specific activity of soluble acid invertase. Subsequent treatment of GA(3) counteracted these effects of Uniconazol. Moreover, the total and reducing sugar content was closely correlated with the soluble acid invertase activity in the stem. It is concluded that the reduction in invertase activity of stem is a biochemical manifestation of the retardation of stem growth induced by Uniconazol.