COMPARISON OF THE CONTENTS OF STARCH, SOL UBLE CARBOHYDRATES AND ABSCISIC-ACID OF LATENT BUDS AND INTERNODES DURING THE VEGETATIVE CYCLE OFGRAPEVINE

In the course of the annual cycle the contents of various soluble suga rs and of starch were determined in buds and internodes of cv. Merlot. In general, the total soluble carbohydrate content was lower in buds compared to internodes; it decreased from July to mid-October, increas ed intensely until December and decreased again until bud burst. The c ontent of hexoses corresponded to this cycle; in buds they were either higher or equal to those of the internodes. Sucrose behaved inversely . Starting in October, the accumulation of raffinose and sucrose was o bviously related to the decrease of the daily average temperatures whi ch possibly confirms their role as cryoprotectors in winter. The conte nts of raffinose in buds which were lower compared to those of interno des decreased after mid-November while in internodes they decreased on ly at the onset of bud burst. Generally, the starch content was lower in buds compared to internodes, its alterations were inversely related to the total soluble carbohydrates. In the presence of leaves the abs cisic acid (ABA) content of buds appeared to affect this development b y inhibiting the accumulation of starch. The decrease of the starch co ntent of buds appears to be associated with the decrease of the ABA co ntent; a decreasing ABA content is assumed to suspend the inhibition o f the a-amylase synthesis. From July to the onset of February ABA is s uggested to inhibit the accumulation of sucrose. Before bud burst decr easing amounts of ABA indicate a development which is inversely relate d to starch but runs parallel to the development of sucrose.