Studies On Modeling For The Morphological Variation Of Cucumber Leaf Based On Micro-mechanics

Plant morphologic modeling and visualizing is the research focus in computer graphics and agricultural engineering in recent years, researchers try to model and visualize the process of plant morphology variation by digital technology.The existing plant morphologic model mainly can be divided into two types:one type model is built by computer graphics scientist, from which lively morphologic images can be obtained. However, the lack of understanding about plant morphology change mechanism lead to this kind of model cannot be used in practical production.Another one is virtual plant model built by researchers in the agricultural engineering, which combined with plant growth process and based on macroscopic experimental, could simulate plant’s response to environment to a certain extent. This kind of model also have not made thorough research about plant morphology change mechanism, so response mechanism of plant to environment can’t be obtained. but it has limitation in practice.Aim at these limitations, this thesis try to establish the macro-morphological change models from the view of "morphologic changes of crop depend on the alternation of cells in it" by using micromechanics. The simulation results were compared with authenticity, they correspond with each other. With the help of the model, requirements of the crop in water, light, temperature can be learnt. The model also can provide a basis of how to control the environmental factors such as water and light. So the research is of great theoretical significance to realize the facility agriculture of high efficiency and sustainable development.1. The alteration of stomason the surface and cells in leaves were examined when leaf water content decreased. When the leaf water content was89.9%, stomas were openmainly, the intercellular space was obvious, the shape of the cells was perfect, chloroplast lamellar was visible. The opened stomas are decreased as leaf water content reduced, when itwas86.5%, only1/3stomaswerein the open state, at the same time leaves began to fold;the cellswere atrophy, the intercellular space became small, chloroplasts were swollen,osmiophilic globulesappeared in them.When leaf water content was75%around, all the stomas on the surface of leaves closedcompletely, the leaf folded further, the intercellular space deceased further,chloroplasts were swollen much more even some of them disintegrated, osmiophilic globule became more and bigger.When the leaf water content decreased to60%around, all the stomas on the surface of leaves closedcompletely, some of them were necrotic, the leaf folded further, the cells shape changed seriously, intercellular space disappeared, and cells glued together, most organelles in the cellsdisintegrated.With the further lack of water, organelles within cells gradually disintegrated, then part of the cell walls disintegrated too.2. The mechanical property of cue μ mber’s mosophyll cell wall was tested by using slicing technique and nano-indentation technology. The results (loading-unloading curve, andstress-strain curve) were analyzed.Results show that when the stress is less than1Mpa, the cell-wall has non-linear elastic characteristics; when the stress is less than0.4Mpa, the nonlinear characteristics of the cell walls weaken, which can be considered as a linear elastic material. In this article, the mechanical property of cell wall was measured after dehydration. Actually cell wall containing a amount of water, so there are certain differences between the two. So in the application of mechanical parameters of the cell wall, the effects of water need to be considered.3.A mechanical model of cue μ mber mosophyll cell (spherical ball filled with liquid)was established by using FEM (finite element method).According to the water metabolism equation, the turgor pressure change caused by transpiration have been calculated. Through mechanical analysis of single cell, dynamics equation of turgor pressure changes over time was obtained.4. A computation model was established to analyzethe impact of cell structure and turgor pressure on the mechanical property of vein, according to the hierarchy structure of vein.5.A computation model was establishedto get mesophyll tissue equivalent mechanical properties by using homogenization method for the first time. The result shows the relation between mechanical property of leaf and water in it. The result also provides an effective basis to calculate the leaf’s macroscopic deformation model. 6.By using of three dimensional laser scanning, reconstruction technique, micro technologies, combined with bio-mechanics, aleaf deformation model under different water conditions is established at the first time. Simulation results of leaf shap and scanned data of real leaf correspond well.The water contents in differentleave which were water stressed were calculated with the model, and the result was compared with the measured data. When the leafwater content change between70%and90%, the coefficient of determination (R2)of independent validation set was0.823,and RMSE is3.4223.7According to light, temperature factor and growth of cucμmber leaf, themodel in which light temperature factor was the driving variables was built to simulate the grow of cucμmber leaf, petiole length and diameter.The leafparameters under different light temperature conditions were calculated by the model. Then,the shape of the leave water stressed were obtained.