Hirotaka Torikata

Effects of Topping at Different Times on the Nitrogen and Carbohydrate Contents and Growth Regulator Activity in Sprouted Lateral Buds of Kyoho Grapevines (Vitis Vinifera L. × V. Labrusca Bailey)

SummarySprouting buds contained the highest levels of N (mostly insoluble protein N) but the lowest levels of sugars in the open in April. The shoot tips later contained less N but more sugars. The same trend as in the shoot tips was observed in buds sprouted by topping at different times until mid-July. However, in August, N increased and sugars decreased. In the clusters of the first or second crops before bloom in an unheated vinyl house the N content was the highest when topped in April and lowest when topped in May, in contrast to the sugar content. Clusters topped on 30 June had increased N and decreased sugars. Cytokinin activities in naturally sprouting buds and those sprouted by topping occurred in three zones of the paper chromatograms of the basic fraction of an 80% alcoholic extract. Total cytokinin activity in the buds decreased markedly as topping time was delayed. Growth-inhibiting activities in the buds were low in May and highest in August. These observations are discussed in relation to ...