Halophytes are plants that live in saline soils. The high osmotic potential of the salt solution in the soil creates a very negative water potential. What can halophytes do so that water will flow into the roots?

Question

A.  They can close their stomata so that less water is lost through transpiration.
B.  They can open all their stomata so that transpiration "pulls" more water into the roots.
C.  They can increase the solute concentration in their roots creating a water potential that is more negative than the soil.
D.  They can pump ions out of the plant creating a water potential in the roots that is more positive than the soil.
E.  They can remove the mycorrhizal fungi from their roots decreasing the competition for water.

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 adaptations that occurs in plants that live in salty environments? 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.  They can increase the solute concentration in their roots creating a water potential that is more negative than the soil.


Clarify Question
What is the key concept addressed by the question?
        · The question addresses adaptations of plants that live in high salt environments.
What type of thinking is required?
                o You are being asked to take what you already know to explain how certain plants can cope with an extreme environment.
What key words does the question contain and what do they mean?
        · Halophytes, which are plants that can tolerate high salt conditions.
        · Saline, which refers a salty environment.
        · High osmotic potential, which is a high solute concentration.
        · Negative water potential, which is a lower proportion of water.

Gather Content
What do you already know about the adaptations that occurs in plants that live in salty environments? How does it relate to the question?
        · In salty soil, the water potential inside the plant is higher than that outside, so plants dry out.
        · Halophytes are salt-loving plants, which can tolerate much higher levels of salt in the soil compared to other plants.
        · Some halophytes add extra ions to their root tissue.
        · The addition of excess ions in the root reverses the usual water potential gradient.
        · Water flows into the plant, from high to low water potential.

Consider Possibilities
What other information is related to the question? Which information is most useful?
        · Stomata must be able to open at some point, or gas exchange would be negatively impacted.
        · If stomata were consistently to remain open, too much water loss would occur.
        · A loss of ions would negatively impact the physiology of the plant.

Choose Answer
Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        · Plants must have water enter through the roots. Water flows from high water potential to low water potential. In salty soil, the water potential gradient causes water to flow out of plants. Halophytes reverse this gradient by pumping ions into the root tissue, thereby creating a lower water potential inside the root. This makes water flow into the roots of halophytes.

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?
        · This question asked you to explain how a halophyte survives extreme conditions. Answering this question correctly depended on your ability to use concept your knowledge of halophytes and water potential in a new situation. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you remember that water potential is greater inside the root of a plant in salty soil, but halophytes can reverse this gradient? Did you have trouble extending the concept of water potential to determine the correct answer?