1. Fill in the following table and use it to answer the following questions (1pt).
|
Mannitol concentration (M)
|
Calculated Osmotic potential of the solution
|
Drop behavior (rise or drop and how fast)
|
Change in length of the potato tissue
|
Change in mass of the potato tissue
|
|
0.05
|
-0.122
|
Sinking slowly
|
1
|
0.22
|
|
0.1
|
-0.243
|
Sinking verly slowy
|
0
|
0.21
|
|
0.2
|
-0.487
|
Sink(slow)
|
1
|
0.03
|
|
0.3
|
-0.730
|
Sink(mid up speed)
|
0
|
-0.03
|
|
0.4
|
-0.974
|
Rise (slow)
|
-1
|
-0.32
|
|
0.6
|
-1.461
|
Rise(mid up speed)
|
-1
|
-0.47
|
|
0.8
|
-1.948
|
Rise (fast)
|
0
|
-0.71
|
|
1.0
|
-2.435
|
Rise (fast)
|
0
|
-0.87
|
2a. Graph the change in weight versus the concentration of mannitol . Draw on the graph how you would estimate the water potential of the tissue.
2b. Graph the change in length versus the concentration of mannitol. Draw on the graph how you would estimate the water potential of the tissue.
3. From your graph what do you estimate the water potential of the potato tissue to be?
4. Does the increase in tissue weight and length resulting from gaining water in the less negative water potential solutions eventually plateau and reach a maximum? Why? Explain this observation based on what we know about the two potential terms that contribute to total water potential in a plants cell or plant tissue.
5. Why would the potato tissue shrink when it loses water (explain this in terms of pressure potential?
6. If you were using this technique with a tissue with very rigid, inelastic cell walls (such as a woody tissue) which measurement method would be least effective? Why?