Observed (bars) and simulated (lines) frequencies of fruit dry weight at harvest (15 September). Simulated values are represented for the four simulated 4-year-old ‘Fuji’ trees. Observed values were recorded on the two digitized 4-year-old ‘Fuji’ trees in 1998 (Experiment 1). The value of the α parameter [eqn (5)] was calibrated directly for the ‘Fuji’ 2 tree using observed data. This value was kept constant for the other trees. The inset graph represents simulated frequencies considering all simulated trees together.