Berlin 2015 – scientific programme
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BP: Fachverband Biologische Physik
BP 15: Posters: Multi-cellular systems
BP 15.4: Poster
Monday, March 16, 2015, 17:30–19:30, Poster A
Diffusion and bulk flow in phloem loading - a theoretical study of the polymer trap mechanism in plants — •Hanna Rademaker1, Julia Dölger1,3, Johannes Liesche2, Alexander Schulz2, and Tomas Bohr1 — 1Technical University of Denmark — 2University of Copenhagen, Denmark — 3Technische Universität Darmstadt, Germany
Plants photosynthesize sugars for storage and growth inside the mesophyll cells of their leaves. In order to distribute them, the sugars are loaded into the phloem vascular system. The osmotic uptake of water increases the pressure in the phloem cells, which then drives the bulk flow throughout the plant, according to the “Münch mechanism” (1930). We studied one special loading mechanism, the so-called “polymer trap”, in which sucrose is believed to diffuse from the mesophyll into the phloem via small symplasmic channels, called plasmodesmata (PDs). Sucrose is then partly converted into larger sugar molecules, which are unable to diffuse back through the narrow PDs. One major concern about this hypothesis was, if sucrose was still able to be transported in sufficient quantity, while molecules less than 20% larger should be completely blocked. Our theoretical study [Dölger et al., Physical Review E 90, 042704, (2014)] shows, that the polymer trap mechanism can in principle function, and that not only diffusion, but also bulk flow, could be involved in the loading mechanism itself, making it more efficient. We are now focusing on experiments, both in plants and in microfluidic devices, testing our theoretical predictions about the symplasmic uptake of water into the phloem.