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Unformatted text preview: November 29, 2006 • Growth – increase in volume or mass • Cell expansion is driven by the uptake of water (in a process called osmosis) • Free Energy – the amount of energy available to do work • Water potential – free energy of water • Molecules move from regions of high free energy to regions of low free energy o Water moves down a potential gradient, from high water potential to low water potential • Factors that influence water potential o Depends on the solute potential Dependent on the concentration of dissolved material (dissolved material lowers ) o Depends on pressure potential Directly influences (increases) potential • Turgor pressure – causes plants to stay upright and important in cell expansion • Convention o Water potential of pure water at atmospheric pressure is 0 Adding solutes loves the water potential, making it a negative number Pressure can be negative or positive • If the cell is compressed, it is positive • If water is being pulled apart, it is negative o Water potential is measured in MPa = megapascals 1 MPa = 10 atm •...
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- Spring '08
- Biology, Xylem