FRUIT SET AND EARLY BERRY DEVELOPMENT IN TWO GRAPEVINE CULTIVARS

Abstract

The growth of the ovary/fruitlet of the beiry of two grapevine cultivars (‘Barbera’ and ‘Freisa’) was investigated at the karyological and histochemical level, in order to study the relationship between mitosis and cell-wall development and the synthesis of polysaccharides. The experiment started when flower buds appeared and continued throughout the formation of fruitlets until early July. In general, the peak of mitosis occurred a few days after fruit set, and the nucellar tissues were affected by the mi- totic processes longer than any other ovary tissues. The growth of the berry was mainly due to the mesocarp cell enlargement It seems that the main components of the cell-wall were pectins, which appeared to be increasing during the mitotic phase of tissue growth. Afterwards, stretching of cell-walls proceeded at a faster pace than pectin synthesis. Differences between the varieties were small but definite, indicating that they may be genotypical.