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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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