1. What is leaf abscission?
A.
The formation of new leaves
B.
The natural shedding of leaves from a plant
C.
The bending of leaves toward light
D.
The enlargement of leaf veins
Correct Answer:
The natural shedding of leaves from a plant
Explanation:
Leaf abscission is the natural process by which leaves separate and fall from the plant.
2. How does auxin generally affect leaf abscission?
A.
It usually delays leaf abscission
B.
It always causes immediate leaf fall
C.
It stops leaf growth completely
D.
It changes leaves into roots
Correct Answer:
It usually delays leaf abscission
Explanation:
Auxin generally prevents or delays leaf abscission, especially when it is present in sufficient amounts.
3. A decrease in auxin concentration in a leaf is commonly associated with which process?
A.
Delayed leaf formation
B.
Leaf abscission
C.
Increased seed germination
D.
Root branching only
Correct Answer:
Leaf abscission
Explanation:
When auxin levels decrease, the leaf becomes more likely to separate from the plant at the abscission zone.
4. The region where a leaf separates from the stem during abscission is called the:
A.
Root cap
B.
Abscission zone
C.
Apical meristem
D.
Stomatal pore
Correct Answer:
Abscission zone
Explanation:
The abscission zone is a specialized layer of cells at the base of the leaf stalk where separation occurs.
5. Applying auxin to the base of a leaf may have which effect?
A.
It may delay leaf shedding
B.
It always causes leaf tearing
C.
It removes all leaf veins
D.
It changes the leaf into a flower
Correct Answer:
It may delay leaf shedding
Explanation:
Auxin applied near the leaf base can maintain the connection between the leaf and stem and delay abscission.
6. Leaf abscission is most likely to occur when the amount of auxin moving from the leaf to the stem:
A.
Increases greatly
B.
Decreases
C.
Remains permanently absent from roots
D.
Changes into chlorophyll
Correct Answer:
Decreases
Explanation:
A decrease in auxin supplied from the leaf reduces the inhibition of abscission and allows leaf shedding to begin.
7. What is one practical use of auxin related to leaf abscission?
A.
Delaying premature leaf drop
B.
Preventing all photosynthesis
C.
Removing roots from seedlings
D.
Producing leaf pigments only
Correct Answer:
Delaying premature leaf drop
Explanation:
Auxin can be used to delay unwanted or premature leaf abscission in plants.
8. During leaf abscission, cells in the abscission zone become:
A.
More easily separated
B.
Permanently fused with root cells
C.
Converted into seeds
D.
Filled with new chloroplasts only
Correct Answer:
More easily separated
Explanation:
Changes in the abscission zone weaken the connection between the leaf and stem, allowing the leaf to detach.
9. Which condition would most likely reduce leaf abscission?
A.
Maintaining adequate auxin near the leaf base
B.
Removing all auxin from the leaf
C.
Increasing damage to the abscission zone
D.
Allowing the leaf connection to weaken
Correct Answer:
Maintaining adequate auxin near the leaf base
Explanation:
Adequate auxin near the leaf base helps maintain the connection and therefore reduces or delays leaf abscission.
10. When a mature leaf begins to fall naturally, auxin usually has:
A.
A stronger inhibitory effect on abscission
B.
A reduced inhibitory effect on abscission
C.
No relationship to the leaf
D.
Changed into a mineral salt
Correct Answer:
A reduced inhibitory effect on abscission
Explanation:
As a leaf ages, the inhibitory effect of auxin on abscission may decrease, allowing separation at the abscission zone.
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