Modeling Sugar Allocations in Plants using Radioisotope Tracer Data Student: Victor Bai, Duke University 15’ Advisor: Dr. Calvin Howell Group: Dr. Alex Crowell, Laurie Cumberbatch, Forrest Friesen

Overview  Background  Goal of Simulation  General Methods  Some Details  Results and Discussion  Future Steps

Growing CO 2 Concentration  Fast increase since the industrial revolution  Carbon is one of the major factors in determining plant growth properties  Need to understand affect of environmental changes on plants

Resource Allocation Mechanisms  CO 2 intake from atmosphere into plant body  Sugar allocation within plant body among leaves, fruits, root, etc.  Adjusting to changes in atmospheric CO 2 level

11 C Nonintrusive Tracking  Produced in the tandem accelerator laboratory at TUNL  Repeat measurements on the same plant  Real time data of 11C events at loop, leave, stem, and root

Overview  Background  Goal of Simulation  General Methods  Some Details  Results and Discussion  Future Steps

Goal of Simulation  Data: 11 C level at each section of plant as a function of time  Models: Diffusion model and press-driven model  To test the models by the data  To determine important model parameters

Overview  Background  Goal of Simulation  General Methods  Some Details  Results and Discussion  Future Steps

Modeling the Plant  Simplifying the plant to a 1D model  Dividing the plant into functional sections  Produce, transport, and/or absorb sugar  Setting up virtual detectors at each section Leaf Upperstem Lowerstem Root

Phloem-Tissue Interaction  Leaf takes in CO 2 and turns it into sugar; Leaf phloem transports sugar without loss  Stem phloem transports sugar while depositing a fraction through surrounding tissue  Root takes the rest

Leaf Bins and Sugar Packets  Leaf divided into bins; Each leaf bin produces one sugar packet at a time  Sugar packets do not interact with each other but with the tissue  Sugar packets diffuse while moving

Overview  Background  Goal of Simulation  General Methods  Some Details  Results and Discussion  Future Steps

Some Details of Simulation Input Parameters:  11 C source loop data from the experiment  CO 2 intake rate  Export and disposition fractions at each section  Movement and diffusion speed at each section Output:  Data arrays and graphs

Overview  Background  Goal of Simulation  General Methods  Some Details  Results and Discussion  Future Steps

Problem with Matching Data  Time delay with total 11 C in plant; only one parameter in control  11 C intake rate cannot be constant in time  Taking time derivative of measurement data and using it as 11 C intake rate

Approximated Parameters

Overview  Background  Goal of Simulation  General Methods  Some Details  Results and Discussion  Future Steps

Possible Future Steps  Further divide stem and root part into bins to do imaging simulations and animations  Add more features to the simulation such as CO 2 absorption delay  Simulate multiple runs under varying conditions (e.g., time of the day, nutrient level, CO 2 sufficiency) and observe changes in plant properties  Use substance flow speed in phloem to determine fluid viscosity constant in the pressure-driven mass flow model

Thank you!