Dynamic simulation model of the transpiration process

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Abstract
Plant life processes are related in a complex way to the balance between the water demand of the atmosphere and the availability of water to the plant root. An exploration of the dynamic status of water in the plant is very important. As an approach to an integrated analysis of the dynamic system of water movement through the soil‐plant‐atmosphere continuum, a simulation model of the transpiration process is presented. Van den Honert suggested the use of Ohm's law describing water flow into, through, and out of plants. In the present study, this hypothesis has been expanded to include an analogous storage factor to deal with the dynamic flow of water in the plant. A set of differential equations and transfer functions is expressed in terms of water suction variables. The dynamic description of the water status in the plant is completed by introducing the system gain, which is a function of both the transpiration rate and the soil‐water condition. The dynamic system gain is realized by a method similar to Corbin's method of a computer‐controlled adaptive control system. The entire system is then simulated on an analog computer; its dynamic characteristics are investigated with consideration of various environmental effects. (Key words: Computers, analog; plants; soil moisture.)