Due to the increasing population and the lack of resources, the demand of plant yield is increasing day by day, and the fact that plant yield cannot meet the demand is more and more significant. Hence, the issue of plant yield optimization becomes a classic topic in the domain of agricultural and forestry management. Plant growth models are widely considered as useful and complementary tools to field experiment. Therefore, it is an important way to investigate the improvement of plant yield using plant growth models. Most of investigations based on process-based plant growth models, while the work based on functional-structural plant growth models is very few. Besides, optimization problems aiming at plant yield improvement may be non-convex and multi-modal; objective functions may not have analytical gradient expressions; for some specific problems like multi-objective optimization problems, optimal results are not unicity. Therefore, in this context, the thesis proposed a methodology for the investigation of plant yield improvement，whose characteristics are as follows: (1) investigations are all based on the functional-structural plant growth model GreenLab and (2) heuristic optimization algorithm and optimal control techniques are applied to the plant growth model in order to improve plant yield. By applying optimization techniques on different species of plants (crops or trees) and for different kinds of optimization problems, common characteristics of a plant with high yield were obtained. The optimal results in the thesis revealed the source-sink dynamics during the plant growth. To achieve the aims of the thesis, the thesis investigated the effects of endogenous factors and exogenous environmental factors of plant growth on plant yield separately. First, given environmental conditions, the thesis investigated endogenous factors, and then the thesis did optimal control on exogenous environmental factors given plant genotype. Therefore, the problems investigated in the thesis consist of general optimization problems and optimal control problems. The main contributions of the thesis include the following issues: 1. According to the species of plants, single-objective optimization problems, multi-objective optimization problems and optimization problems with constraints with respect to plant endogenous factors were formulated and investigated, in order to find the ideotype of plants with high plant yield. All optimization problems were solved by a ...
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