[The effect of gibberellic acid and indoleacetic acid on the root formation of tomato cuttings].

Root formation of tomato cuttings was always inhibited by GA, never promoted. The number of roots was reduced and the roots appeared later, so that at the end of the experiment (13 days later) a reduced dry weight resulted. The effect depended on the concentration of GA, the lowest effective concentration being 10(-3) mg/l. Root formation decreased up to 1000 mg/l GA. An effect on the shoot was noted at concentrations above 10 mg/l. Counts of root primordias after 3-5 days showed the same diminution of root formation. The growth of existing primordias seemed not to be influenced by GA.Short-time treatments with GA had a smaller effect, but a 3-day absorption-period resulted in the same decrease as a treatment during the whole experiment. When GA was given after the experiment had started, the first 3 days of treatment were again the most effective. This result shows that the induction of root primordias is inhibited or at least retarded.CCC had no effect on root formation nor was it able to alter the inhibition by GA. IAA alone did not promote the rooting process. In combination with GA (concentration range for both 10(-3)-1 mg/l) IAA never reduced the inhibition by GA. On the contrary, 1 mg/l IAA+GA was somewhat more inhibitive than GA alone.