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 13C as well as the soluble acid invertase activity. The application of Uniconazol, (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-tnazol-1-yl)-1-pentane-3-ol, reduced the growth of stems and leaves without affecting the roots. In addition, the translocation of assimilated 13C 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 GA3 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.clarify some physiological aspects involved in the Uniconazolinduced morphological changes in Zinnia elegans Jacq.
MATERIALS AND METHODS
Plant Material and CultivationSeeds of Zinnia elegans Jacq. cv Red Sun were sown in plastic boxes (35 x 45 x 8 cm) with vermiculite and germinated in a growth chamber in the dark at 25°C. After germination, the seedlings were transferred to a glasshouse. When the cotyledons were fully expanded, the seedlings were transplanted to vinyl pots (7 cm in diameter and height) with sand. Growth retardants generally affect plant growth by causing a reduction in internode growth and an increase in root growth (2, 3, 7). We also reported that Uniconazol, which is known to block the biosynthetic step from ent-kaurene to ent-kaurenoic acid, decreased the stem length as well as the shoot/root ratio but increased the leaf/stem ratio (9). A detailed experiment revealed that the growth retardant Pix increased the root/shoot ratio, translocation of '4C-assimilates, and allocation of more biomass to the root sink in sugar beet (6). Thus, it seems that growth retardants reduce the sink activity in the stem and increase it in the root.Sink activity has been closely linked with gibberellin action. Some studies suggest that GA3 promotes the increase of sink activity or rates of phloem unloading in the stem, but does not affect assimilate production or phloem loading at the source (5,10,14,15,19). Sink activity is reflected in the activity of invertase which hydrolyzes phloem-translocated sucrose into hexose substrates available to growing cells. In addition, invertase activity is positively correlated with the concentration of hexose sugars (12,13,16). Thus, the physiological changes in sink activity induced by growth retardants which have an antagonistic effect on GA3 (1,8, 9) can be ascribed to GA3-mediated metabolic processes.In this paper we investigated the distribution of assimilated '3C as well as the soluble acid invertase activity in order to
GA3 and Uniconazol TreatmentsThe different tre...
