LOCALIZATION OF TANNINS IN GRAPE BERRY SK INS

The localization of tannins in grape berry skins has been studied by a ssociating results obtained with two methods: light and transmission e lectron microscopy, and chemical analysis of the fractions obtained af ter isolation of cells as protoplasts. According to their location, th ree groups of tannins were determined. The first consists of free tann ins in solution in the vacuolar sap (these tannins appear in the form of granules decreasing in size from the skin surface to the pulp). Two other groups are constituted by bound tannins: those bound to the pro teins of the internal face of the tonoplast, and those bound to the ce ll wall polysaccharides by osidic bonds.