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LABORATORY 1b - Water Potential II

LABORATORY 1b: WATER POTENTIAL II
OVERVIEW
In this laboratory you will investigate the effect of solute concentration on water potential as it relates to living plant tissues.

OBJECTIVES
Before you begin this lab you should understand: - the mechanisms of diffusion and osmosis and their importance to cells - the concept of water potential - the relationship between solute concentration, pressure potential and the water potential of a solution - the concept of molarity and its relationship to osmotic concentration **also read the section on water potential in the text book ** (Chapter 36 pp. 749-751 in 6th ed. of Biology by Campbell, Reece & Mitchell) At the completion of this lab you should be able to: - measure the water potential of a solution in a controlled experiment - determine the osmotic concentration of living tissue or an unknown solution from experimental data - describe the effects of water gain or loss in animal and plant cells - relate osmotic potential to solute concentration and water potential [NOTE: You may want to look over Lab 1a to refresh your memory!]

EXERCISE 1b-A: DETERMINING THE WATER POTENTIAL OF POTATO CELLS
In this exercise you will use potato cores placed in different molar concentrations of sucrose in order to determine the water potential of potato cells. First, however, we will explore what is meant by the term "water potential." Water Potential. Water potential is abbreviated by the Greek letter psi (ψ). Water potential measures the tendency of water to leave one place in favor of another place. Water will always move from an area of higher water potential to an area of lower water potential. In animal cells, movement of water into and out of a cell is influenced by the relative concentration of solute on either side of the plasma membrane. Water will move by osmosis in the hypoosmotic → hyperosmotic direction. If water moves out of the cell, the cell will shrink. If water moves into
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