Study On The Cell Mechanics Behavior Of Plant Tissue And Application In Fruits Mechanical Damage

It is well known that growth of plants is stimulated by environment, such as windows and stress. The stress induced growth is a concern problem all along by biologist, physicist and mechanical scientist. Professor Feng Yuanzhen who is an exploiter about biomechanics said the relationship between stress and growth is a live atman of biomechanics. The study of plant biomechanics is also alike. People has known that the mechanical stress influence botanic growth long before. The previous works shown that a series of complex physiological and chemical responses are brought in inside of organism by external forces. The complex physiological and chemical responses depend on the type and the strength of the applied forces. The mechanical stress excitement has considerable influence on the botanic growth and configuration. But the reason of the stress induced growth is not clear. To understand the stress induced growth, the study of the transference and distribution of the external force in the cells level inside of the tissue is a key problem. The knowledge about the transference and distribution of the applied force inside the fruit tissue in the cell level is very important for the study of the fruit damage. But few references could be found in this area. Although, a lot of works have been done on the fruit damage by means of experiment methods.The primary goal of the dissertation is to study how the applied forces transfer and distribute inside plant tissues in the cell level, and the relationship between the external force and turgor, as well as the stress of the cell wall. Furthermore, the fruits damage will be studied from a new point of view-梩he force applied on the cells.According the structural characteristic of the plant call, a hexagon mechanical model for plant cell was proposed. Then, using the mechanical theories and finite element method, the deformation, wall stress and turgor for plant cells, under compression and shear, was analyzed. The advantage of the proposed cell model is that it's much convenient to integrate to form a tissue by cells. ANASYS software was used to compute the deformation, wall stress and turgor for single cell and tissue. While the cell deformation or distortion, the volume of the plant cell keeps un-changed. This is a very important constrain for the deformation or distortion of plant cells. A method that could make the results satisfy the equilibrium equations as well as the constrain equations was developed.The proposed method was used to analyze the damage of apple tissue. The simulated results were in good agreement with experimental data.Moreover, according to the electric charges distributing characteristic of the plant cell membrane, a formula about cellular pressure produced by the charges was deduced. The effect of the charges distributed on the cell membrane on the cell pressure was discussed.Finally, a mechanical model for grape or tomato kind of fruits was discussed. The mechanical parameters were evaluated by cure fitting of the experimental data. From this model, the deformation, stress of the grape skin and the change of the inner-pressure was obtained. It was found that the change of the volume for unit of force is a constant.