Transport213-page12 - Transport in Plants - 12...

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Transport in Plants - 12 Transpiration is also be responsible for some water and dissolved ion movement from soil into the roots. When transpiration rate is high, the osmotic gradient across the endodermis decreases as dissolved ions are drawn upward in the xylem. The depletion of water in the root hair zone can draw water from surrounding soil areas. Although the transpiration-cohesion explanation for water movement through xylem is "widely" accepted, many questions remain and water movement through xylem is an active area of research in plant physiology. For example, some vessel walls are lipid lined, so no water adhesion occurs in such vessels. Others question the accuracy of pressure bombs and other mechanisms for measuring water potential. In addition, the rate of water movement in xylem is not uniform within "equivalent" regions of plants. Transpiration-cohesion is surely a force in water movement through xylem. As techniques improve, as with all science, better explanations may result.
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This note was uploaded on 01/08/2012 for the course BIO 213 taught by Professor Makina during the Fall '09 term at SUNY Stony Brook.

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