Synergism between Gibberellin and Auxin in the Growth of Intact Tomato

Abstract

Gibberellin A4&7 was: more effective than gibberellic acid in increasing sboot elongation wben applied to the apex of intact Lycopersicum esculentum seedlings of Tiay Tim, a dw,arf cultivar, and Winsal!, a tall cultivar. After 14 days, gibberelHc acid and gibberellin A4&7 stimulated growth of the dwarf more than the tall tomato. In tall tomato the application of indole-3-acetic acid alone (6.1 |Jg/plant) showed an inhibitory growth effect, bat when applied with 17.5 [ig per plant of gibberellic acid, it bad a synergistic effect at 7 days but not at 14 days. When the auxin concentration was reduced to 0.61 |,ig per plant a synergistic effect was observed on tall plants at 7 and 14 days between indole-3-acetic acid and gibberellic acid. Application of gibberellin A4&7 witb auxin did not give a synergistic response in tall or dwarf tomato.

Organization and expression of the TUP gene in Daucus carota

“…They observed that only auxin contributed to the division of the cells in the cambium, but that the relative ratios of auxin and gibberellin could shift the formation of phloem (high gibberellin) or xylem (high auxin). A study by Grunwald and Lockhard demonstrated that gibberellin could reverse the inhibition of auxin on stem-elongation and also that the growth regulators acted synergistically, enhancing stem elongation (40). Aloni showed that in Coleus blumei, auxin and gibberellin together could replace the effect of leaves in the control of phloem fiber formation (41).…”