engleski

Negative pressure in osmosis at constant volume and water uptake in tall tree

A thermodynamic state of solvent and solution separated with an elastic semipermeable membrane, in the box with a fixed volume, is considered. It is shown that the minimum value of free energy is accompanied by the compression of the solution and tension of the solvent [1-4]caused by the transfer of solvent molecules into compartment with solution . The tensile state of the solvent is described in terms of negative pressure. Due to the elastic properties of membrane the difference of pressure between compartments is less than osmotic pressure calculated with van't Hoff equation. However, it is still enough high to uptake water in tall trees. It is proposed that osmosis at constant volume could be responsible for the water uptake in tall trees. Using plausible arguments it is shown that embolism is followed with refilling in this process [5-7]. In other words embolism repair is possible in osmotic process under constant volume. References [1] Hirsch, H.R. “Gedanken Experiment”: Negative Solvent Pressure in Osmosis. J. Biol. Physics, 1980, 8, 11-13. [2] Freeman , R.D. Comment on Hirsch’s “Gedanken Experiment”: Negative Solvent Pressure in Osmosis. T J. Biol. Physics, 1981, 9, 47. [3] Hirsch, H.R. Further comments on Negative Solvent Pressure in Osmosis. J. Biol. Physics, 1983, 11, p. 26. [4] Scholander, P.F. The Role of Solvent Pressure in Osmotic Systems. Botany, 1966, 55, 1407-1414. [5] Zimmermann, U., Schneider, H., Wegner, L. H. and Haase, A. Water ascent in tall trees: does evolution of land plants rely on a highly metastable state? New Phytol., 2004, 162, 575-615. [6] Holbrook, N.M. and Zwieniecki, M.A. Embolism Repair and Xylem Tension: Do We Need a Miracle? 1999, Plant Physiology, 1999, 120, 7–10, [7 ] Zwieniecki, M.A. and Holbrook, N.M. Confronting Maxwell’s demon: biophysics of xylem embolism repair. Trends in Plant Science, 2009, 14, 530-534.

thermodynamic state; osmotic pressure; free energy; negative pressure; tall trees

nije evidentirano