Solute Accumulation by Grape Pericarp Cells V. RELATIONSHIP TO BERRY SIZE AND THE EFFECTS OF DEFOLIATION

Coombe, B. G., Bovio, M. and Schneider, A. 1987. Solute accumulation by grape pericarp cells. V. Relationship to berry size and the effects of defoliation.—J. exp. Bot. 38: 1789-1798. We have studied the accumulation of water, dry matter (DM) and glucose and fructose (G + F) in selected grape berries cv. Dolcetto of varying initial size growing on leafed and defoliated vines. The first measurements at 2 d after veraison were obtained non-destructively from correlations with linear dimensions and deformability; the final measurements were made when the berries were harvested 13 d later. The increments in DM and G + F per pericarp increased with initial berry size thus discounting an hypothesis of an equal amount of solutes supplied to all berries. The increments in weight of DM and G + F per increment of pericarp volume were constant in berries of different size, supporting an hypothesis of a control determined by concentration in the solution available for accumulation in all berries. Defoliation reduced the increments per pericarp and per g fr. wt. by about the same proportion and its effects were consistent with the above interpretations. Key words—Grape pericarp, sugar accumulation, phloem unloading, Vitis vinifera. Correspondence to: Department of Plant Physiology, Waite Agricultural Research Institute, Glen Osmond, South Australia 5064, Australia.