Modeling And Simulation Of Interaction Between Water And Plant Growth

Virtual plant is a kind of technology which simulates plant growth that iscontrolled by physiological processes and driven by environment in three-dimensionalspace and to show the growth process with visualization technologies based oncomputer. It has potential applications including agriculture, forestry, ecology，remotesensing and other subjects. On the one hand, interaction between environment andvirtual plant is one of the key techniques and also is one of the difficult and hot spots inresearch on virtual plants. On the other hand, although botanists have already studiedthe interaction between plant and environment，it is difficult to describe thoseprocesses through the mathematical model and simulate those processes bycomputer. Water deficit stress known as drought stress is commonly encountered.Permanent or temporary, it limits growth and distribution of natural vegetation andperformance of cultivated plants more than any other environmental factors do. Thegoal of the paper is to model plant and water environ interaction and demonstrate plantphysiological and morphological responses to water deficit stress by3Dvisualization.The main studies and contributions in this dissertation are as followings①A growth model for interaction between plant organs and water isconstructed.A index called water deficit degree（WDD） is defined to estimate waterstatus of whole plant by including three factor：water deficit intensity，water deficiduration and plant resistance to water deficit.A water transport electrical-circuit analogymodel is used to estimate plant single organ water potential which is defined to describelocal organ water status.The feedback between plant growth and water is achieved bymodeling the organ sink with water potential and WDD using source sink model.Amaize dataset under different water regims is used to validate the proposed model. Theresults show that the model can simulate morphological changes of maize organs underwater deficit well during vegetation growth stage.②A root system model based on hydrotropism is proposed. Voxel technology isused to subdivide root growth zone.3D Rachirds equation is used to simulate thedynamic process of soil water distribution and interaction between soil water and rootarchitecture.The space colonization algorithm is used to sense direction of hydrotropismand then direction of root growth will be synthetical by hydrotropism, gravitropism and original growth direction. Water uptake and root length fraction alongdeep affected by hydrotropism are analyzed. L-Systems are used to control rootgrowth and development and interaction with soil water. The results show that theproposed method can demonstrate root structure influenced by hydrotropism effectively.③A growth model for interaction between whole plant and water is constructed.To solve defect for plant aboveground and underground parts separate study, a tieredwater transprot model is proposed to calculate water potential of aboveground organsand effect of belowground soil water transport induced by transpiration. Aftercalculating water potential the aboveground organs, flux of root segment is calculatedaccording to Kirchhoff’s current law and then the sink term of Richards equation will bemodified to simulate root water uptake and soil water transport driven by transpiration.The water potential characteristics of plant different locations are analysed with changesin soil water potential. The growth process of whole plant is simulated in different waterdeficits. The results show that the method can be able to fill the gap betweenaboveground and underground parts study separately, and to achieve the goal tosimulate the plant as a whole under water deficit.④A set of simulation woftwre to support the interactive model are research anddevelopmentresearch and developmentresearched and developed completely. Base onthe concept ot virtual organ, oriented object program language(JAVA) is used toprogram aboveground, root system and the whole palnt interaction with water inWindows operation system on Eclipse platform. JAVA3D graphics library is used forvisualization of simulation results. Matlab is used for visualization of soil waterdistribution and water uptake.