Based on a functional-structural plant model - GreenLab, the source-sink relationships were investigated in order to analyze the impact of fruit sink strength on the plant biomass production and partition for an optimal yield in the case of maize. The fruit sink strength optimization comes from the fact that there is competition between the fruit and the leaves in demand of biomass according to the results of GreenLab model calibration. A theoretically optimal fruit sink strength value was therefore acquired by solving a bound-con strained optimization problem to act as an evaluation criterion for the species of maize growing in the field, and we name the optimal value fruit sink reference. The optimization results hold with fruit weight se...