New contribution to the survey of the acrotony theory on the branch of one year grapevine: III - Role of buds and leaves in development, application in the vineyard of results obtained in laboratory and greenhouse

The respective influences of the bud and leaves on stimulation of acrotony phenomenon was studied. Defoliation (all leaves at the stage budbursted + 30 days) and various bud ablation were made : buds 9, 10 ; 7, 8, 9, 10 ; 5, 6, 7, 8, 9, 10 ; 3, 4, 5, 6, 7, 8, 9, 10. Concerning the phenomen of acrotony, the role of apical bud and leaves developped on at 10 and 30 days after budburst were determined. The effect produced by excision of the apical buds shows that the two subadjacent buds were developped. All decapitation did not increase the percentage of budbreak. In all decapitations, the subadjacent buds were developped however, buds below were inhibed. The effect produced by excision of leaves in the second stage of development did not promote budbreak. On 10 bud canes, auxins synthesized in the developing young leaves seem to exercise their inhibiting effect on the budbreak of the subjacent buds. Cytokinins managed by the means of our operatory mode seem to reach the subjacents buds, modify the expression of the ramification of the canes with regard to the system usual acrotony and limit the inhibition basipetally. The budburst of the canes at a temperature of 18°C seems to be more important than that at 30°C day/ 20°night. Thus, the acrotony phenomenon decreases. When the apical branches are in second phase of growth, the size of the leaves become large. It seems that the leaves would exercise their inhibitions on the subjacent buds by the slant of the synthesized gibberillins and auxins. Cytokinins have no further role to play during this phase of growth and do not thwart anymore the inhibition. In the vineyard, the ANA treatment is totally inhibiting at 20 and 50 mg/l doses. In contrast, the 6BAP treatment at 20 mg/l shortly before budburst increases the budburst percentage for Muscatel of Italy. When the last treatment is performed during 25 days followed by a cytokinin treatment we notice budburst. The mechanism of these different growth regulators on the acrotony phenomenon has been discussed