ISHS Acta Horticulturae 179: V International Symposium on Growth Regulators in Fruit Production
EFFECTS OF GROWTH REGULATOR TREATMENTS ON THE HORMONE PATTERN IN THE TRUNK AND THE COLLAR TISSUE OF APPLE TREES |
| Authors: | A. Karaszewska, B. Jankowska, M. Mika, M.J. Grochowska |
| Abstract:
It is well known that sprays with growth retardants bring about more return bloom in these trees whose flowering can be suppressed by gibberellins. It has been assumed that growth retardants as well as other growth regulators affect growth and flowering in plants by altering hormone balance. Three year results of applications of growth regulators to young apple trees cvs McIntosh and Melba showed that changes in growth and flowering induced by the treatments were accompanied by a vast alteration in endogenous patterns of auxin, gibberellin and cytokinin-like substances. Alterations in activities of endogenous growth substances extracted from the vascular strands of the trunk plus branches and determined by bioassays were different in upper versus lower part - the collar - of the trunk. Daminozide plus Ethrel, 1000+500 mg/dm3, sprays doubled return bloom and reduced shoot extension by 27 to 35 percent compared to those of controls on Melba and McIntosh trees, respectively. It was followed by a decrease in activities of auxin and gibberellin-like substances and a restrain of a natural, dramatic fall of free and bound cytokinins in the collar tissue. Applications of gibberellic acid suppressed the return bloom and caused an increase of auxin and gibberellin-like substance levels. The collar part showed an ability to reduce activity and convert endogenous gibberellins to less polar than gibberellic acid. | |
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