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Consequences of phloem pathway unloading/reloading on equilibrium flows between source and sink: a modelling approach
Peter E H Minchin1, André Lacointe2
1The New Zealand Institute for Plant and Food Research Ltd (PFR), 412 No. 1 Rd, Te Puke 3182, New Zealand.
Functional Plant Biology : FPB
|June 3, 2020
Summary
Phloem transport is leaky, requiring photosynthate reloading. Modeling reveals pathway unloading significantly impacts solute concentration and pressure, but reloading can mask these effects on source-sink dynamics.
Area of Science:
- Plant Physiology
- Biophysics
- Computational Biology
Background:
- Transport phloem is known to be leaky, with considerable photosynthate unloading.
- This unloading necessitates reloading to maintain long-distance phloem transport.
- Pathway unloading/reloading acts as a buffer for source and sink fluctuations.
Purpose of the Study:
- To model pressure-driven flow incorporating pathway unloading and reloading of carbohydrates.
- To determine the effect of these processes on source-sink dynamics.
- To investigate if reloading can compensate for unloading effects.
Main Methods:
- Development of a novel model for pressure-driven flow in transport phloem.
- Inclusion of both carbohydrate unloading and reloading within the pathway.
- Analysis of solute concentration and hydrostatic pressure profiles.
Main Results:
- Phloem flow deviates from Poiseuille dynamics.
- Pathway unloading significantly alters solute concentration and hydrostatic pressure.
- Sufficient reloading can completely mask the effects of pathway unloading.
Conclusions:
- Simple measurements of solute concentration or pressure are insufficient to understand phloem flow mechanisms.
- Pathway unloading and reloading are critical factors influencing source-sink dynamics.
- The interplay between unloading and reloading can create a dynamic equilibrium within the phloem system.
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