The Relative Importance of Fruits and Leaves for the Cultivar-Specific Growth Rate of Apple Fruits

SummaryFruit growth rate was measured for different ratios of fruit number and leaf area on twin-top trees, where the two parts consisted of either Golden Delicious or of Graasten, or of one of each cultivar. Leaves and fruits were removed in advance in different ways; and in one treatment leaves on one top section supplied fruits on the other top section. The growth rate for a given fruit number/leaf area ratio was higher in Graasten than in Golden Delicious fruits. No clear difference was detected between treatments where the fruits of one cultivar was supplied by leaves of its own and those where they were supplied by leaves of the opposite cultivar. Distances between leaves and fruits, up to at least one metre, did not reduce the fruit growth rate at a given fruit/leaf ratio compared to normal fruit-leaf distribution. On the other hand the dry matter percentage of the fruit decreased at the greater distances.