Modeling Water Uptake by Plant Roots

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Modeling Water Uptake by Plant Roots Powered By Docstoc
					                               Modeling
                               Water Uptake
                               by Plant Roots
by Stacy Kish, CSREES          With funding from USDA’s Cooperative        management problems, such as soil
                               State Research, Education, and              quality, water and nutrient requirements
                               Extension Service (CSREES) National         and climate change.
With changes in climate,       Research Initiative (NRI), Mario Biondini        The WBE model uses the geometry
farmers and ranchers must      at North Dakota State University found      of network systems for resource
contend with diminishing       a way to more accurately predict water      exchange to predict the chemical
water resources. One of the    uptake from plant roots by improving        reactions required for life sustaining
best ways to deal with this    upon the West, Brown and Enquist            functions in biological organisms. This
                               (WBE) general model for scaling laws        model has been used in plant vascular
challenge is to maximize
                               in biological networks.                     systems to model the movement of
the efficiency of plant root
                                     Researchers use models                water and nutrients in the xylem and
systems, and researchers
                               extensively to test various agricultural    phloem, the two types of transport
in North Dakota are taking     research questions and natural resource     tissue in the above ground parts
steps to do just that. >>                                                  of plants.
                                                                                                   continued next page >>




                                                                                                                            nri_impact_048_09_23_08_root model.pdf, pg. 1/2 | CSREES Communications Staff




Right: Root system for
a fertilized 20 months old
Stipa comata (needle and
thread).
Credit: Mario Biondini
                                                   >> continued from previous page


                                                   The WBE model was designed for closed
                                                   systems, where materials are exchanged
                                                   only at the tip of the network. Therefore,
                                                   the WBE is not the ideal model
                                                   for predicting water uptake in open
                                                   systems, such as the root systems
                                                   of plants, where water can be
                                                   exchanged throughout the entire
                                                   network.
                                                        Maximizing water uptake in plant
                                                   roots requires balancing two types of
                                                   flow throughout the network. The first
                                                   involves minimizing the resistance to
                                                   flow inside the network, the longitudinal
                                                   flow. The other involves maximizing
                                                   water flow into the network, the
                                                   transversal flow. Mathematically, the        demand or soil/water distribution.
                                                   longitudinal flow is inversely               In the model, Biondini used a simplified
Above: A Ph.D. student on the project
setting up the trickle irrigation experiment.      proportional to the fourth power of          version of a root system that still
Credit: Mario Biondini                             the root radius, while the transversal       captured the flow dynamics of the
                                                   flow is inversely related to the radius      entire network.
References                                         of the root.                                       Plant diversity and the sustainability
Johnson, H. and M.E. Biondini. 2001. Root               Biondini modeled the optimal root       of managed ecosystems are, in part,
morphological plasticity and nitrogen uptake       radius for water uptake and transfer for     highly dependent on the volume of
of 59 plant species from the Great Plains
                                                   any arbitrary volume and branching           soil explored by root systems and the
grasslands, U.S.A. Basic and Applied Ecology
2:127-143.                                         configuration. Model results were tested     density and distribution of those root
Biondini, M. E. 2001. A three dimensional          with data collected from 1,759 plants        surfaces. Accurate modeling of root
spatial model for plant competition in a           belonging to 77 herbaceous plant             systems and their nutrient and water
heterogeneous soil environment. Ecological         species. Other parameters considered         uptake, thus, is an essential tool for
Modelling 142:189-225.
                                                   in the model included soil type and          the planning and implementation
Levang-Brilz, N. and M.E. Biondini. 2002.          drainage.                                    of modern agro-ecosystem practices.
Growth rate, root development and nutrient
uptake of 55 plant species from the Great Plains        Results suggested that the root               CSREES funded this research project      nri_impact_048_09_23_08_root model.pdf, pg. 2/2 | CSREES Communications Staff

Grasslands, U.S.A. Plant Ecology 165:117-144.      scaling configuration that maximizes         through the NRI Managed Ecosystem
Biondini, M.E. 2007. Plant diversity,              water uptake is independent of water         program. Through federal funding and
production, stability, and susceptibility                                                       leadership for research, education and
to invasion in restored northern tall grass                                                     extension programs, CSREES focuses
prairie (United States). Restoration Ecology
15:77-87.
                                                                                                on investing in science and solving
                                                                                                critical issues impacting people’s daily
Biondini M.E. 2008. Allometric scaling laws
for water uptake by plant roots. Journal of                                                     lives and the nation’s future. For more
Theoretical Biology 251:35-59.                                                                  information, visit www.csrees.usda.gov.