ISHS Acta Horticulturae 146: International Workshop on Controlling Vigor in Fruit Trees
ENDOGENOUS AUXIN AND GIBBERELLIN LEVELS IN LOW AND HIGH VIGOR APPLE SEEDLINGS |
| Authors: | Maria J. Crochowska, George J. Buta, George L. Steffens, M. Faust |
| Abstract:
Endogenous auxin and giberellin levels in the vascular tissue of two groups of apple seedlings with low and high vigor were analyzed during two consecutive seasons. Auxin-like activity in the phloem of the low vigor seedlings was much higher than that of the high vigor trees. A maximum auxin activity occurred in these seedlings in July and remained high until October. The onset of high auxin activity coincided with swelling of the terminal shoots. Levels of gibberellin-like substances in the phloem were also higher in the low vigor seedlings compared to that of the high vigor trees and the maximum occurred in July. Gibberellins found in the xylem and assumed to be produced in roots were very high at the beginning of the growing season and decreased dramatically in June. Polarities of the gibberellin-like substances differed in the seedlings. Levels of the gibberellins more polar than GA3 were markedly higher in the low vigor seedlings than that of the high vigor ones. | |
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