Revisiting the Münch pressure—flow hypothesis for long-distance transport of carbohydrates: modelling the dynamics of solute transport inside a semipermeable tube

• Published in: Journal of experimental botany 2002-06, Vol.53 (373), p.1411-1419
• Main Authors: Henton, S.M., Greaves, A.J., Piller, G.J., Minchin, P.E.H.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Algorithms; Biological and medical sciences; Biological Transport; Carbohydrate Metabolism; Coefficients; Computer Simulation; Diffusion; Diffusion Chambers, Culture - instrumentation; Diffusion coefficient; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Mathematical models; Metabolism; Modeling; Models, Biological; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Osmotic Pressure; Phloem; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology; Plant physiology and development; Plant Structures - physiology; Plants; Regulation of Growth, Development and Whole Organism Physiology; Sieve tubes; Solutes; Sucrose - metabolism; Time Factors; Viscosity; Water - chemistry; Water - metabolism
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jexbot/53.373.1411

A mathematical model of the Münch pressure—flow hypothesis for long-distance transport of carbohydrates via sieve tubes is constructed using the Navier—Stokes equation for the motion of a viscous fluid and the van't Hoff equation for osmotic pressure. Assuming spatial dimensions that are appropriate for a sieve tube and ensuring suitable initial profiles of the solute concentration and solution velocity lets the model become mathematically tractable and concise. In the steady-state case, it is shown via an analytical expression that the solute flux is diffusion-like with the apparent diffusivity coefficient being proportional to the local solute concentration and around seven orders of magnitude greater than a diffusivity coefficient for sucrose in water. It is also shown that, in the steady-state case, the hydraulic conductivity over one metre can be calculated explicitly from the tube radius and physical constants and so can be compared with experimentally determined values. In the time-dependent case, it is shown via numerical simulations that the solute (or water) can simultaneously travel in opposite directions at different locations along the tube and, similarly, change direction of travel over time at a particular location along the tube.