Hassan Aref Memorial Lecture & Fall Fluid Mechanics Symposium Invited Lecture*

Sap Flow and Sugar Transport in Plants

Thursday, November 21, 2013

11:00-12:00, Assembly Hall, The Inn

Dr. Tomas Bohr

Technical University of Denmark

 Plants have highly effective vascular systems, which can transport fluid over large distances. The xylem system carries water from the roots up to the leaves and the phloem system carries sugar solutions from sources (leaves) to sinks (roots, fruits etc.) and thus provides the necessary material for growth. There are many important fluid dynamical problems connected with these flows, and I shall discuss some of them. In the 1920’ies, Ernst Münch proposed that sugar transport in the phloem is driven by passive osmotic pressure gradients generated by loading and unloading sugar into the phloem tubes (sieve elements) of the leaves. It has been strongly debated whether this hypothesis can actually account for long distance translocation, e.g., from canopy to root of a large tree. In the lecture, I will argue that optimization of the efficiency of the sugar transport leads to a universal scaling of the width of the phloem tubes with the loading (leaf) length and the translocation (stem) length in plants. These predictions have been tested for plants ranging from 10 cm herbacious plants to 60 m trees – both hardwood and conifers – and provide the first quantitative test of Münch’s ideas. For both the xylem and the phloem, the leaves provide the driving force for the sap flow, and I shall discuss current ideas how this complex feat is accomplished.

The lecture is partly based on recent papers:

K. H. Jensen, J. Lee, T. Bohr, H. Bruus, N. M. Holbrook & M. A. Zwieniecki: Optimality of the Münch mechanism for translocation of sugars in plants, Journal of the Royal Society Interface 8, 1155–1165 (2011)

K. H. Jensen, T. Bohr & H. Bruus:  Osmotically driven flows in microchannels separated by a semipermeable membrane, Lab on a Chip 9, 2093-2099 (2009)

K. H. Jensen, J. Liesche , T. Bohr & A. S. Schulz: Universality of phloem transport in seed plants, Plant, Cell & Environment 35, 1065-1075 (2012)

K. H. Jensen, K. Berg-Sørensen, S. Friis & T. Bohr: Analytic solutions and universal properties of sugar loading models in Münch phloem flow, Journal of Theoretical Biology 304, 286-296 (2012)

K.H. Jensen, D.L. Mullendore, N.M. Holbrook, T. Bohr, M. Knoblauch & H. Bruus: Modeling the hydrodynamics of phloem sieve plates, Frontiers in Plant Science 3, article 151 (2012)

L. S. Haaning, K. H. Jensen, C. Hélix-Nielsen, K. Berg-Sørensen & T. Bohr: Efficiency of osmotic pipe flows, Physical Review E 87, 053019 (2013)

*This is a joint seminar co-sponsored by the Department of Engineering Science and Mechanics, the Department of Mechanical Engineering, and the MultiScale Transport in Environmental and Physiological Systems (MultiSTEPS) program.

2013 Summer Graduate Workshop on Connecting Biological Data with Mathematical Models

The 2013 Summer Graduate Workshop on Connecting Biological Data with Mathematical Models will be held June 17-28, 2013, at NIMBioS on the campus of the University of Tennessee, Knoxville. The workshop is co-sponsored by NIMBioS, MBI and the Centre for Applied Mathematics in Bioscience and Medicine (CAMBAM). The workshop features instructors from across North America whose research expertise is mathematical modeling in biological systems using real data. Some of the techniques to be covered include Maximum likelihood and Bayesian approaches to inference, parameter estimation, model identifiability, uncertainty and sensitivity analysis, and data assimilation. Applications of connecting data to models will come from epidemiology, ecology (including global change biology), evolution, microbiology, physiology, pharmacokinetics, and systems biology.

Graduate students from the mathematical, physical and life sciences are encouraged to apply. There are no fees associated with this workshop and most meals are included. If needed, the math institutes can provide some support (transportation, lodging) for Workshop attendees.

Dates: June 17-28, 2013

Location: NIMBioS at the University of Tennessee, Knoxville

Co-sponsors: NIMBioS, MBI, and Centre for Applied Mathematics in Bioscience and Medicine (CAMBAM).

Application Deadline: January 15, 2013

For more information about the workshop and a link to the online application, go to http://nimbios.org/education/WS_grad2013

VT Interdisciplinary Research Symposium on November 2

Registration is open for the Second Annual Interdisciplinary Research Symposium, held at Virginia Tech on Nov 2nd, 9am-3pm,  in the Graduate Life Center (GLC) Multipurpose room!

The Interdisciplinary Research Honor Society (ΙΔΡ) organizes this symposium to promote interdisciplinary work being performed at Virginia Tech by graduate and undergraduate students. Dr. Bill Newell, a leading scholar on interdisciplinary research, will be the keynote speaker and host an interactive panel discussion.

Additionally, undergraduate and graduate students will present their research in poster sessions and compete for poster awards in their respective categories. Coffee and lunch break provided. Registration is free! To register go to symposium.idrsociety.org.

IDR Day 2012 coming soon

2nd IDR Day, Tuesday, April 10, 5:00-9:30 pm, The Inn at Virginia Tech

The Interdisciplinary Research Honor Society (IDR) is sponsoring the 2nd Interdisciplinary Research Day (IDR Day 2012) at Virginia Tech. Enjoy an evening of exciting discussions about transdisciplinarity and interdisciplinarity. At the beginning of the event we will welcome our new honor members into the society and review this year’s accomplishments. Then the audience will subdivide into groups to tackle modern-day wicked problems through creative integration of the different disciplines represented in the group. Dinner is provided. Registration is FREE but required due to limited spaces. All students, faculty and staff are encouraged to attend. For the event program and registration, please go to:


MultiSTEPS team meeting with Dean DePauw on Feb 13

The meeting with Dean DePauw and Dr. Aigster has been set for Monday, Feb 13, from 12-1pm in Dean DePauw’s conference room.

This conference room is located in the Graduate Life Center.  Enter through the glass doors that face Squires.  Walk through the lobby (black & white floor), up the (central) lobby stairs, to the elevator.  Select “2R” on the elevator panel.  When you exit – the  conference room is in the right wing of the building, on the left side of the hall, Room 238.

The meeting will involve, at least in part, a discussion of this blog site.