Plant modeling, which has found a wide use in many fields such as agriculture, forestry and computer graphics, is an intercross field involving botany, mathematics and computer science. In recent years, functional-structural plant modeling (FSPM) became the main topic in this field. GreenLab model, which was developed by French and Chinese researchers, is one of the well-known FSPM models. GreenLab model has been developing because of the complexity of the plant. Most researches about this model are focused on the biomass generation and allocation. Nevertheless, influence outside the plant, such as pruning and light, is also important. The motivation of this thesis is to do some computing experiments and try to simulate the response of the plant through internal mechanics under some conditions. An implementation of GreenLab model, whose name is QingYuan, is firstly described. A software platform is essentially needed for computing experiments. As it was written in C++, which is well-known for its efficiency and the feature of object-oriented design method, QingYuan had advantages in speed, completeness of implementation and flexibility comparing to other GreenLab implementations. The first kind of computing experiment is pruning. Most previous works used some statistical equations to describe the result of pruning. In our work, an assumption is introduced to simulate the pruning effect. The underlying assumption is that the source-sink ratio will be increased while pruning because less organs will consume biomass, which will consequently result in the change of plant architecture. In the tree pruning experiment, four strategies are tested in the same cycle and the final crown shape looks real. In the cucumber pruning experiment, also four strategies are tested and the quantity and quality of fruits are discussed. The second kind of computing experiments is light competition. Ray tracing is used to implement a simple algorithm which calculates light distribution in crown. Under the assumption that a bud will not develop unless the visibility of the leaf above this bud is larger than a threshold, we can simulate the light competition between two adjacent trees. This method avoids some complex geometrical algorithm such as collision detection. Plant model based on cycles is not accurate enough for the simulation of plant response of outside influence. Model based on more accurate time scale is needed. The development of an axis in one year, together w...
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