In your garden, you have an Ailanthus altissima, also known as the Tree-of-Heaven. You try adding additional plants to the same garden bed, but notice poor seed germination and seedling growth around the tree. What is the most likely explanation for this?

Question

A.  The tree is blocking most of the available sunlight which is limiting germination and growth.
B.  The tree is utilizing most of the available miconutrients in the soil.
C.  The roots of the tree have a stronger water potential than the seedlings which is causing the seedlings to dehydrate.
D.  The tree has a mutalistic relationship with animals that are removing plants that are in competition for resources with the tree.
E.  The tree is releasing chemicals into the soil that are inhibiting germination and growth of other plants.

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 about plant interactions? 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

E.  The tree is releasing chemicals into the soil that are inhibiting germination and growth of other plants.

Clarify Question
· What is the key concept addressed by the question?
        o This question is asking you to identify the reason that plants are not growing around a Tree-of-Heaven.
· What type of thinking is required?
        o This question is asking you to evaluate the reason for lack of germination and growth in plants that occur around a Tree-of-Heaven.
· What key words does the question contain and what do they mean?
        o Tree-of-Heaven, which is one of the names for the deciduous tree with the scientific name Ailanthus altissima.
        o Germination, which is the process of plant growth from a seed.

Gather Content
· What do you already know about about plant interactions? How does it relate to the question?
        o Certain plants put allelopathic chemicals into the soil, which inhibits the growth of other plants around them.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o Other trees have plants that grow around them, even if sunlight is blocked.
        o It is not likely that a tree would usurp so many of the micronutrients in the soil that other plants would be inhibited in both germination and growth.
        o The question describes inhibited growth, not removal of plants by animals, which would look very different.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The inhibition of both germination and growth is very suggestive of a chemical agent at work in the soil that would inhibit both of these processes.

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?
· Evaluate level:
This question asked you to explain why plants are inhibited around the Tree-of-Heaven. Answering this question correctly depended on your ability to evaluate normal growth of one plant and relate it with lack thereof in nearby plants. If you got the correct answer, well done! If you got an incorrect answer, where did the process break down? Did you remember that allelopathy causes the very effects of inhibition that are described in the problem?