In magnesium-deficient plants the older leaves show more severe symptoms of chlorosis which is a yellowing of the leaves than younger leaves. What is the best explanation?

Question

A.  There is more time for the symptoms to develop in older leaves.
B.  Chlorophyll is transported from the older leaves to the younger leaves.
C.  Magnesium is more soluble in younger leaves.
D.  Scarce magnesium is removed from older leaves and translocated to support younger, more active leaves.
E.  Older leaves need less chlorophyll.


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

Gather Content
· What do you already know about the importance of magnesium in chlorophyll? 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

D.  Scarce magnesium is removed from older leaves and translocated to support younger, more active leaves.

Clarify Question
· What is the key concept addressed by the question?
        o Magnesium is an important component of chlorophyll.
· What type of thinking is required?
        o This question is asking you to weight and judge, or evaluate, the consequences of magnesium deficiency in plant tissue.
· What key words does the question containand what do they mean?
        o Magnesium, which is an essential macronutrient in plants that is a component of chlorophyll.
        o Chlorosis, which is a condition that causes a yellowing of the leaves due to insufficient chlorophyll production.

Gather Content
· What do you already know about the importance of magnesium in chlorophyll? How does it relate to the question?
        o Magnesium is a component of chlorophyll.
        o Chlorophyll reflects green wavelengths of light, which gives plants their green color.
        o Leaves that are deficient in chlorophyllturn yellow.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o The hydrocarbon tails of chlorophyll molecules attach to membranes in the chloroplast.
        o The age of a leaf does not necessary mean that it needs less chlorophyll.
        o If a plant is magnesium deficient, at least initially leaves would be impacted equally.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
       o To answer this question, you must connect the idea that chlorophyll synthesis requires magnesium with the effects of the removal of magnesium from plant tissues.

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 a change in leaf coloration . Answering this question correctly depended on your ability to weigh and judge, or evaluate, the structure of the main plant pigment, chlorophyll and the effects of the decline of chlorophyll in plant tissues. If you got the correct answer, well done! If you got an incorrect answer, where did the process break down? Did you remember that magnesium is a critical component of chlorophyll, or the criteria to compare old and new leaves includes the synthesis of chlorophyll in new leaves?