Abscisic acid (ABA) is synthesized in the roots in response to decreased soil water potential. ABA then translocates to the leaves, where it rapidly alters the osmotic potential of guard cells. What effect would this have on the stomata and the process of transpiration?

Question

A.  The stomata would open thereby increasing the rate of transpiration.
B.  The stomata would open thereby decreasing the rate of transpiration.
C.  The stomata would close thereby decreasing the rate of transpiration.
D.  The stomata would close thereby increasing the rate of transpiration.
E.  The change in the stomata would have no effect on the rate of transpiration.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

Gather Content
· What do you already know about the relationship between transpiration and stomata? How does it relate to the question?

Consider Possibilities
· What other information is related to the question? Which information is most useful?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  The stomata would close thereby decreasing the rate of transpiration.

Clarify Question
· What is the key concept addressed by the question?
        o The question is asking about the role of stomata in transpiration.
· What type of thinking is required?
        o This is an analyze question because you have to break the stomata and transpiration into their component pieces to understand how they function.
· What key words does the question contain and what do they mean?
        o Stomata, which are openings on leaves.
        o Guard cells, which regulate the stomata.
        o Transpiration, which is the evaporation of water from plant leaves.

Gather Content
· What do you already know about the relationship between transpiration and stomata? How does it relate to the question?
        o Abscisic acid (ABA) plays an important role in the opening and closing of the stomata.
        o Stomata regulate water loss from the leaves.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o Decreased water flow into the plant would not cause the stomata to open.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Decreased soil water potential would result in a reduced water flow into the plant.
        o To prevent dehydration, ABA would signal the guard cells to close.
        o Closed guard cells would reduce transpiration and prevent dehydration.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
· Analyze level:
        o This question asked you to understand the factors that regulate transpiration. Answering this question correctly depended not only on distinguishing between the roles of different hormones, but on your ability to break down, or analyze, the effects of hormones on the stomata and transpiration. If you got the correct answer, excellent! If you got an incorrect answer, where did the process break down? Did you remember that ABA influences stomatal activity, or that stomata regulate transpiration? Did you have trouble breaking down the functions of the hormones to determine the correct answer?