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Long-distance hormone transport via the phloem
Heather L Collis1, Markus R Owen1, Leah R Band2
1Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
Journal of Theoretical Biology
|January 20, 2023
Summary
Plant hormones travel through the phloem to the root tip, regulating growth. This study models sugar and hormone transport, revealing that increased sugar loading and unloading enhance hormone delivery to the root tip.
Area of Science:
- Plant Biology
- Mathematical Modeling
- Physiology
Background:
- Key plant hormones are synthesized in shoots and transported via phloem to the root tip, where they regulate growth and environmental responses.
- Understanding how environmental factors influence hormone delivery to the root tip is crucial but limited.
Purpose of the Study:
- To develop a mathematical model of sugar and hormone transport in the phloem.
- To investigate the relationship between sugar dynamics and hormone transport velocity.
- To determine how environmental factors affect hormone delivery to the root tip.
Main Methods:
- Developed a mathematical model of osmotically driven flow in a pipe, incorporating spatially varying membrane properties for phloem loading and unloading.
- Formulated solute membrane transport with passive and active components.
- Included solute unloading via bulk flow using the Staverman reflection coefficient.
Main Results:
- The model predicts that increased active sugar loading, increased bulk flow sugar unloading, or decreased root sugar concentration enhances phloem transport velocity.
- Increased phloem transport velocity leads to greater hormone delivery to the root tip for passively loaded hormones.
Conclusions:
- Environmental factors influencing sugar transport dynamics directly impact hormone delivery rates to the root tip.
- The model provides a framework for understanding how phloem transport influences plant hormone signaling and root development.
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