A Synthetic Tree Grows at Cornell | Wired Science from Wired.com

Link: A Synthetic Tree Grows at Cornell | Wired Science from Wired.com.

2008/09/16 see comment for an additional pointer (thanks to Gauthier Chapelle) that provides more information and relates this research may help explain how trees can grow above 34 feet in height.

"Scientists have made the world's first synthetic tree: a palm-sized duplication of the elegant process by which trees drink."

Tobias Wheeler and Abraham Stroock of Cornell University have emulated the abilty of xylem to tranport water using "hydrogel-embedded capillaries" which allow water to evaporate and create presure differentials.  The concept could be applied to creating a transport mechanism for heat within a building.

The paper The transpiration of water at negative pressures in a synthetic tree [Nature] points out that "the differences in pressure generated in plants to drive flow can be more than a hundredfold larger than those generated in synthetic wicks."  The microfluidic system captures many of the key characteristics of plan transpiration, including:

• "transduction of subsaturation in the vapour phase of water into negative pressures in the liquid phase"
• "stabilization and flow of liquid water at large negative pressures (-1.0 MPa or lower)"
• "continuous heat transfer with the evaporation of liquid water at negative pressure"
• "continuous extraction of liquid water from subsaturated sources"

Comments

[NH]

Additional information is available at http://www.technologyreview.com/Biotech/21382/?nlid=1347&a=f. The article explains the implication of 'metastable states'. Water cannot be 'pulled' to a height exceeding 34', since the pressure exerted by a column of that height just balances the pressure of the atmosphere through the roots. This is a well-known problem with the old 'hand crank' farm pumps and was solved by submersible pumps that push water from below.

The transpiration-pull theory should therefore retrict trees to 34 feet, yet sequoias reach 370 feet. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/X/Xylem.html suggests a number of solutions.

Thanks to Gauthier Chapelle for the pointer!