Flower bud dormancy in Coffea arabica L.; 2: Relation of Cytokinins in xylem sap and flower buds to dormancy-release
Two cationic, butanol-soluble, cytokinin fractions were resolved from purified coffee flower bud and xylem sap extracts. Dormant buds yielded only the more polar fraction and xylem sap collected during drought the less polar fraction, levels of the latter fraction decreasing as drought proceeded. When bud dormancy was broken by irrigation or rainfall, a rapid increase occurred in the more polar cytokinin of the xylem sap. Activity of both cytokinin fractions increased in the buds also, but more slowly at first. The pattern of changes in both bud and sap cytokinin indicate that, when water stress in coffee trees is relieved, cytokinin, which may be required by the buds for further development to anthesis, is releases from within the xylem. This, it is suggested, explains why water stress usually must be relieved before the buds can emerge from dormancy. Using thin-layer chromatography, the more polar cytokinin was found to be chromatographically indistinguishable from zeatin riboside inthe six different solvent systems tried, while the mobility of the less polar one was similar, but not identical, to 6 (̓̓dimethylallyl) amino purine. A technique for the sequential extraction of gibberellins, abscisic acid and cytokinin is described
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| Format: | biblioteca |
| Subjects: | COFFEA ARABICA, FISIOLOGIA, FLORACION, LATENCIA, YEMA (PLANTA), XILEMA, COMPOSICION, CITOCININAS, DORMANCIA, YEMAS FLORALES, |
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