Variations in kinetin-like activity in buds of Betula and Populus during release from dormancy

Abstract

Levels of kinetin-like activity in dormant buds and buds at various stages of release from dormancy were determined by an assay involving retardation by kinetin-like substances of chlorophyll degradation in tissue of senescing leaves of Raphnrzus test plants. Dormancy of buds of Betlrlapapyrifera and Poprrhrs balsarnifera cuttings was broken by exposure to 2-chloroethanol vapor or immersion in warm water. Water extracts of buds at various stages of dormancy were separated by ascending chromatography and active R f values identified. The amount of kinetin-like activity at various stages of bud dormancy was then determined by observing effects of active R f values of bud extracts on senescence (cl~lorophyll retention) of Raphanus plants. Kinetin-like activity was absent in dormant buds of both species and was present in various amounts after dormancy was broken. In Betula, such activity was found primarily at R f values of 0.3 to 0.5, and secondarily at 1.0. In Poprrllrs, kinetin-like activity was found at Rr values 0.5 to 0.6 and 0.9 to 1.0. Kinetin-like activity was greater in non-dormant buds of Popul~rs than in those of Betuln. However, the trend of variation in activity with time after breaking of dormancy was similar in both species. After bud dormancy was broken, kinetin-like activity in both species increased progressively until shortly before buds opened, and it decreased thereafter. Evidence is cited that release of buds from dormancy involves a change in the balance of growth regulators, with various growth promoters increasing to overcome the effects of inhibitors. Endogenous cytokinins appear to be involved, together with other growth promoters, in regulating release of buds from dormancy.

Does Ethylene Play a Role in the Release of Lateral Buds (Tillers) from Apical Dominance in Oats?

“…A more rapid rate of prophyll elongation follows this swelling phase. This pattern of swelling and elongation has been described for bud break from dormancy in woody plants (9). Buds in isolated stem segments incubated in 10-5 M kinetin (a concentration found to induce significant tiller release in oats [12]) and 0.1 M sucrose also exhibit an early prophyll swelling phase followed by prophyll elongations (Fig.…”

Environmental and Hormonal Control of Turion Germination in Myriophyllum Verticillatum

“…However, the classes of hormones which are most frequently found to be important are the gibberellins and the acidic inhibitors, particularly abscisic acid. There is also some evidence for the involvement of cytokinins (Chvojka, Travnicek and Zakourilova, 1962;Domanski and Kozlowski, 1968;Hewett and Wareing, 1973).…”

Culture of Shoot Apices of Theobroma cacao

“…This is also true of other species ie.g. Domanski and Kozlowski 1968, with Belula and Populus, Hewitt and Wareing 1974, with Populus X robusta, and Borkowska 1976. Cytokinins thus appear to be involved in the breaking of bud dormancy and the results obtained here with kinetin suggest a close involvement of kinins in the control of the cocoa flush cycle.…”