Distribution of Solutes within the Developing Grape Berry in Relation to Its Morphology

Abstract

Grape berries taken at four stages of ripeness (from veraison to overripeness) were dissected to give 19 segments representing divergent tissues and their content of eight solutes measured. Each solute was found to have distinctive space and time patterns of variation in concentration. In general, solutes that did not accumulate massively (sucrose, phenols, potassium, inorganic anions, and tartrate) were in low concentration in the flesh and in higher concentrations in the skin and brush. Those that did accumulate massively (malate at veraison and glucose and fructose thereafter) had higher concentrations in the flesh than in the skin and brush. Tartrate was high in peripheral flesh at veraison, and potassium was low in peripheral and adjacent flesh at all stages. High levels of sucrose and inorganic anions were found in central flesh of overripe berries. Gradients in malate were created by the low concentrations in segments containing vascular tissue, both peripheral and central, presumably due to malate respiration by this tissue. In one year, but not in the next, a large zone of the flesh of overripe berries extending around the seed from the skin to the opposite empty locule was found to have abnormally high concentrations of many solutes, possibly caused by a localized dehydration of these tissues.