The continuum theory provides a framework in which the growth
of a plant root as a dynamic process involving interactions among
transport of water and solute, cell division, and the subsequent cell
elongation can be described. A plant root is modeled as a one-dimensional,
multi-phase, mathematical continuum. The network of cell
walls constitute the solid phase of the system. The symplast and the
apoplast pathways reside in this network of cell walls. Water and
carbohydrates move in opposite directions through the apoplast and
symplast pathways within the deforming network of cell walls. The
division and elongation of cells depends on the mechanical stress imposed
on the cell walls, the rate of metabolic stress relaxation process, and the
physical properties of the cell walls.
The model consists of five systems of differential equations. The
kinematic equations are derived which allow, specifically, the different
roles of cell division and elongation in root growth to be considered.
These provide the reference system of the model. Equations of water
transport in the coupled system of apoplast and symplast pathways are
derived from considerations of theories of transport in the porous media
and the cellular and membrane properties of the plant root. Equations of
solute transport are derived by considering, specifically, the mechanisms
involved in solute transport both at the membranes separating individual
cells and within the cytoplasm. The rate of cell elongation is described as
a function of the mechanical stress in the cell walls, the viscoelastic
properties of the cell walls, and a metabolically controlled strain energy
relaxation process. Growth in the meristem is modeled as the result of
continuous cell elongation and division.
The equations of water and solute transport, cell elongation, and
meristem growth are solved simultaneously under the reference system
provided by the kinematic theory. The model is used to examine the
effects of soil water stress, soil resistance to root penetration, and
temperature, as well as the carbohydrate supply from the upper part of
the plant on the dynamic process of root elongation. The close
correspondence between the material coordinate system and the underlying
cellular structure of the root allows the comparison between the
continuum theory and the results of cell growth studies. Agreement of the
model predictions of the pattern of growth along the root axis, as well as
the effects of temperature and soil water stress on root growth, with the
experimental measurements reported in the literature provides the
justification for the theories. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37093 |
| Date | 22 August 1990 |
| Creators | Feng, Yongsheng |
| Contributors | Boersma, Larry |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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