engleski

The significance of the xylem-phloem coupling in the upward water transport in plants

Xylem is modelled as the closed system coupled to the root and phloem via semi-permeable membranes. The importance of the fixed volume of the xylem in the osmotic process between xylem and phloem is analysed. It is shown that negative pressure, a concept accepted as a driving force for the upward xylem water transport in many scientific discussions, is closely related to this process. It is shown that there is a self-consistency between decrease of the pressure in the xylem and increase of the concentration of the sugar in phloem, respectively, in dependence of the height. [1] Zimmermann, U., H. Schneider, L. H. Wegner, and A. Haase. 2004. Water ascent in tall trees: does evolution of land plants rely on a highly metastable state? New Phytol. 162:575-615. [2] Lampinen, M. J., and T. Noponen. 2003. Thermodynamic analysis of the interaction of the xylem water and phloem sugar solution and its significance for the cohesion theory. J. Theor. Biol. 224:285-298.

xylem; osmotic; phloem; height; water transport; negative pressure

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