Bond Graph Aided Hydraulic Flow Model of Plant in Response to Physical and Environmental Factors

Abstract

With the increase of imbalance in ecosystem and natural chaos researchers have been putting focused effort in evaluating the behavior of biological plant communities in response to various environmental and physical factors. Therefore, understanding of water transport in soilplantatmosphere continuum is essential for the management of ecosystem. The first objective of this present research is to get a comprehensive picture of the physical principles behind transportation of water from soil to roots and then in the plant up to the aerial parts. The work is inter-disciplinary in nature. From the physical principles, a mechanical model for a simplified plant consisting of one root, a stem and a big leaf that deals with the water dynamics of vegetation is derived. This mechanical model is put into bond graph notation which deals with the water dynamics within the plant, called the hydraulic flow model. The hydraulic flow model is a mechanistic model based upon plant physiological behavior which is used to study functionality of different plant organs in handling water flow. Different resistance elements are introduced into the model corresponding to various sections of the plant out of which stem xylem resistance and stomatal resistance are modeled. Stem xylem resistance is modeled by taking diurnal change of stem xylem diameter into account. The resistance model of stomata is developed with the help of Jarvis-Stewart model for stomatal resistance. The process of transpiration is also incorporated into the model which is developed with the help of Ohm’s law analogy. Thermal behavior of the vegetation is introduced by taking boundary layer, aerodynamics, ambient temperature, relative humidity and global solar radiation into account. Calculations are mostly done for specific kind of plants and for specific sight. Finally, various environmental and physical influencing factors are considered to study the response of the model which offers novel modeling tactics alternative to the field measurements.