Practice important
Leaf Senescence
MCQ questions and answers.
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MCQ Questions
1. What is leaf senescence?
A.
The aging process of a leaf
B.
The formation of a new leaf
C.
The opening of stomata
D.
The absorption of water by roots
Correct Answer:
The aging process of a leaf
Explanation:
Leaf senescence is the natural aging process of a leaf, during which its functions gradually decline.
2. Which visible change commonly occurs during leaf senescence?
A.
The leaf becomes permanently blue
B.
The leaf turns yellow
C.
The leaf develops new roots
D.
The leaf becomes a flower
Correct Answer:
The leaf turns yellow
Explanation:
During leaf senescence, chlorophyll breaks down, causing the leaf to lose its green color and often turn yellow.
3. Which green pigment is degraded during leaf senescence?
A.
Chlorophyll
B.
Hemoglobin
C.
Melanin
D.
Keratin
Correct Answer:
Chlorophyll
Explanation:
Chlorophyll is degraded during leaf senescence, leading to the loss of green color in aging leaves.
4. What happens to photosynthesis during leaf senescence?
A.
It gradually decreases
B.
It increases continuously
C.
It changes into respiration
D.
It stops only in roots
Correct Answer:
It gradually decreases
Explanation:
As leaves senesce and chlorophyll breaks down, their ability to carry out photosynthesis gradually decreases.
5. Which plant hormone can promote leaf senescence?
A.
Abscisic acid
B.
Auxin
C.
Gibberellin
D.
Cytokinin
Correct Answer:
Abscisic acid
Explanation:
Abscisic acid can promote leaf senescence, especially when plants experience stress or aging.
6. What is one important function of leaf senescence for a plant?
A.
Recycling nutrients from old leaves
B.
Producing more chlorophyll in old leaves
C.
Increasing leaf size indefinitely
D.
Preventing all water loss from roots
Correct Answer:
Recycling nutrients from old leaves
Explanation:
During leaf senescence, useful nutrients are broken down and transported from the aging leaf to other parts of the plant.
7. Which process is closely associated with the final stage of leaf senescence?
A.
Leaf abscission
B.
Seed germination
C.
Root branching
D.
Fruit formation
Correct Answer:
Leaf abscission
Explanation:
Leaf senescence is often followed by abscission, in which the aging leaf separates and falls from the plant.
8. Why does an old leaf lose much of its green color during senescence?
A.
Because chlorophyll is broken down
B.
Because more chlorophyll is produced
C.
Because the leaf absorbs extra sunlight
D.
Because the leaf forms new stomata
Correct Answer:
Because chlorophyll is broken down
Explanation:
The breakdown of chlorophyll is a major event in leaf senescence and causes the leaf to lose its green appearance.
9. Leaf senescence is best described as a process that occurs mainly in which type of leaf?
A.
Aging leaf
B.
Newly emerged leaf
C.
Underground root
D.
Unopened flower
Correct Answer:
Aging leaf
Explanation:
Senescence is the natural aging process of a leaf after it has completed much of its functional life.
10. What may happen to proteins in a leaf during senescence?
A.
They are broken down and their nutrients may be recycled
B.
They are changed into chlorophyll
C.
They permanently stop all plant growth
D.
They form the leaf cuticle only
Correct Answer:
They are broken down and their nutrients may be recycled
Explanation:
During leaf senescence, proteins can be degraded and their nitrogen-containing nutrients may be transported to growing parts of the plant.
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Leaf Senescence
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