Gibberellin-Treated Shamouti Oranges: Effects on Coloration and Translocation Within Peel of Fruits Attached to or Detached from the Tree

The inhibitory effects of gibberellins on color changes associated with maturation of Shamouti oranges were studied. Quantitative estimation of color changes showed that gibberellins had similar effects on fruit detached from or attached to the tree, no matter whether gibberellin was applied to the whole fruit or only to a small part of its surface. However, detached fruits overcame the effect of gibberellin relatively quickly, while attached fruits were influenced for several months. A logarithmic dose-response curve was obtained with detached fruit in the range of 0.1-3.1 mg/l GA3. GA1, GA3, GA4, GA5, and GA7 were found to be almost equally effective; but GA8 and GA9 had only a slight effect. The presence of a green, gibberellin-induced spot extending beyond the border of the treated zone was taken as an indication for translocation of gibberellin in the fruit peel. Attached fruit seemed to mobilize gibberellin to a greater distance than detached fruit and also showed a trend of translocation toward the stylar end of the fruit.