In this paper we report a model for coupled transport of water and organic solutes in xylem and phloem of soybean plants. The mathematical model is based on compartmental representation of the physical and chemical processes that generally control transport in plants and is thus applicable to other plant. Each compartment is characterized by its volume, thickness of cell wall, diffusion, reflection, and partition coefficients of the cell membranes, sorption of chemical, and loss of chemical due to degradation or to immobilization in growing tissue. Anatomical features of the compartments and the manner in which they are connected are described by a series of equations based on conservation of mass.
As an example we apply the model to a single-leaf and single-root representation of a soybean plant. Using literature values for the coefficients that describe the model, we calculated the distribution of a solute for conditions of constant transpiration in which the chemical is assumed to be passively transported throughout the plant. Simulations demonstrate the role of the several parameters of the model on transport and tissue retention. Specifically, effects of partition coefficients, reflection coefficients, first-order loss rates, compartment volumes, and rate of transpiration flux are shown.
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