1. Consider a plant 20 cm tall growing in well watered soil. Ina dark and humid

ID: 4106 • Letter: 1

Question

1. Consider a plant 20 cm tall growing in well watered soil. Ina dark and humid greenhouse, in

the middle of the night, you measure the turgor pressure of aliving leaf cell of this plant using

a probe inserted in the cell. You find that the turgor pressureis 1.9 MPa. Given the current

conditions, what is your prediction of the osmotic potential ofthis cell?

2. If you were to study a similar cell (from question 1), undersimilar environmental conditions

(night, saturating humidity, turgor pressure = 1.9 MPa), foundat the top of a redwood tree on

a misty night in California. How would your prediction of theosmotic potential change if you

knew that the cell was located at the top of a 100 m tall tree?Explain the reason for the

change in your prediction using the water potentialequation.

3. Use water potential terminology to explain why many smalltowns, particularly those in flat

regions, have water towers. Create a brief example to illustrateyour point.

4. Examining the labeling patterns from the six paperchromatography panels below, label the

figures from 1-6 in the order of increasing time since theapplication of the labeled pulse of

CO2. Briefly explain how this information allows us to drawconclusions about the reactions

that make up an important biochemical process like the Calvincycle.

5. There are some plant pathogens that release compounds calledsurfactants into the water in

the xylem. One of the effects of adding surfactants to water isthat the surface tension of

water is decreased. Identify two ways that the presence ofsurfactants in the xylem solution

might influence the water relations of the plant.

Surfactants decrease the cohesion of water, lowering the forceof bulk flow and preventing water from reaching the photosyntheticareas of the plant.

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