Co-Authors:
Wallerstein, I., Department of Ornamental Horticulture, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
Hackett, W.P., Department of Horticultural Science and Landscape Architecture, University of Minnesota, St. Paul, MN, United States
Abstract:
Mature Hedera helix plants were treated with gibberellic acid (GA3) either as a pulse of 80 μg /plant or as a continuous application of 10, 25, 50, or 100 μg GA3/plant for 50 days. Both methods of application were to the stem, 0.5 cm below the apical bud. With both methods, a direct dose-related promotion of elongation and prevention of scale production (quiescence) followed the start of GA3application. Ancymidol at 560 or 2800 μg /plant quantitatively retarded stem elongation and caused quiescence of the treated plants. The indirect effect of GA3, which was observed at all the concentrations 22 or 34 days after the end of pulse or continuous treatments, respectively, consisted in the gradual appearance of morphological changes typical of rejuvenation, i.e., aerial roots, an- thocyanin accumulation, change in stem shape, reduction of meristem size, and change in phyllotaxis and leaf shape. Under continuous GA3treatment, juvenile characteristics were not evident on the main stem, but did occur on lateral branches. Continuous application for 50 days of TIB A at concentrations of 10-5M or 10-6M following the pulse application of GA3retarded the elongation caused by GA3; at a concentration of 10-5M, TIBAprevented the production of aerial roots. TIB A applied continuously at a concentration of 10-6M to plants not treated with GA3prevented scale production and caused production of aerial roots 20 days after the end of the treatment. Two months after cessation of continuous application, the apical meristems of plants treated with 10-5M TIB A were very similar to juvenile meristems. © 1989 Taylor & Francis Group, LLC.