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Unformatted text preview: of the trunk, and most xylem is actually under a tension, a phenomenon that helps to explain how water appears to move upward throughout the plant. Ultimately it was been demonstrated that the loss of water through transpiration, discussed earlier, plays a significant role in water movement throughout the xylem. • Water lost by transpiration creates a negative water potential in cells that exerts a “pull” on the H 2 O in cell walls that is connected (by cohesion) to H 2 O in xylem resulting in a strong tension in the xylem. • As water evaporates out of the stomata, the film of water that coats mesophyll cells diminishes. Primary cell walls have adhesive properties; the remaining water is attracted to the walls (cellulose is very hydrophilic – think of the paper towel commercials), resulting in even less water and the water potential of the mesophyll cells decreases....
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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.
- Fall '09