1. UNI Plant Physiology Spring 2005
Water Movement
UNI Plant Physiology
Spring 2005

2. Three Rules WP = PP + SP Membrane? Water flows from high to low
Yes?…Osmosis happens: WP determines flow
No?... Bulk flow happens: PP determines flow
Water flows from high to low

3. Ask yourself Is there a membrane? What are the WPs or PPs?
Choose WP or PP
What are the WPs or PPs?
Which one is lower?

4. Write it down, Say it out loud
Write down the arithmetic
Draw the arrow showing flow
Explain it in words
Helps you understand and remember
Prepares you for tests

5. Now do the problem set Don’t go any further in this presentation until you have done everything you can on your own. Reading about solving problems is like reading about swimming. You will drown if you read, then jump in the deep end of the pool.

6. Done the problem set yet
Done the problem set yet? OK, time to check the thinking and the answers. Read and answer the questions before clicking to continue. Watch carefully: something happens with each click. Page Up to go back & see it again.

7. Two limp, wilting leaf cells
Is there a membrane here?
Yes (one for each cell)
Water potential is what counts
Calculate water potentials
SP + PP = WP
Write them in as you go
= ? -4
= ? -2 -4 -2
Which water potential is lower?
-4 is lower than -2 (like temperature)
Draw arrow to show water flow.

8. Two ordinary (stiff) leaf cells
Is there a membrane here?
Yes (one for each cell)
Water potential is what counts
Calculate water potentials
SP + PP = WP
Write them in as you go
= ? -2
= ? -1 -2 -1
Which water potential is lower?
-2 is lower than -1 (like temperature)
Draw arrow to show water flow.

9. Two xylem “cells” (pipes)
Is there a membrane here?
No (membranes gone—only walls left)
Bulk flow (everything together)
Pressure potential is what counts
Don’t have to calculate water potentials
Just look at the pressure potential
-1 and -2
Which pressure potential is lower?
-2 is lower than -1 (like temperature)
Draw arrow to show water flow.

10. Ordinary cell next to xylem “cell”
Is there a membrane here?
Yes (for the live cell)
Water potential is what counts
Calculate water potentials
SP + PP = WP
Write them in as you go
= ? -3
-1 + (-1) = ? -3 -2
Which water potential is lower?
-3 is lower than 0 (like temperature)
Draw arrow to show water flow.

11. That’s all Just follow all the steps Write, draw, explain
One at a time
In order
Write, draw, explain
Let me know if this was helpful
Tell me if you spot any errors