Scientific Programme

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Plants tell us how liquids can be transported under negative pressure

Monday (16.03.2020)
16:20 - 16:40
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Plants are the only living organisms that can transport water over long distances under negative pressure. How exactly plants are able to do this represents a long-standing question in biology. So far, man-made evaporation-driven transport devices failed, unless these were based on pure and completely degassed water, which is not the case for plant sap. The central goal of our work is to test novel insights in our understanding of water transport in plants to both natural and synthetic systems based on centrifuge experiments. This approach allows us to create water flow under negative pressure, while controlling the solution, temperature, and tension of the system. Our results show that flow under negative pressure works well for stem segments, but is almost impossible in open capillaries. Stem segments of hazel (Corylus avellana) show that 50% loss of the maximum hydraulic conductivity is achieved at -1.7 MPa. Moreover, mesoporous media inside stems, with pore constrictions between 5 and 20 nm, are found to play a crucial role in water transport under negative pressure. Cellulase treatment of stem segments, which results in the removal of the mesoporous media between water conducting cells, indicates that embolism occurs as soon as the tension reaches negative pressure. We hypothesise that mesoporous media are foam-producing structures, which keep gas bubbles tiny and stable by a surfactant coat, without causing immediate embolism and hydraulic failure of the system. An important challenge ahead is the integration of inert mesoporous media into artificial stems to develop synthetic trees. The development of an artificial tree could be useful for cooling systems, various biomedical applications, or pump systems that do not rely on fossil fuels.

Dr. Christophe Trabi
Ulm University