1. What does leaf abscission mean?
A.
The formation of new leaves
B.
The natural shedding of leaves from a plant
C.
The opening of leaf pores
D.
The movement of water into leaves
Correct Answer:
The natural shedding of leaves from a plant
Explanation:
Leaf abscission is the natural process by which mature or damaged leaves separate and fall from the plant.
2. Which plant hormone is commonly associated with promoting leaf abscission?
A.
Ethylene
B.
Auxin
C.
Cytokinin
D.
Gibberellin
Correct Answer:
Ethylene
Explanation:
Ethylene promotes the formation and activity of the abscission layer, leading to leaf shedding.
3. What is the abscission zone?
A.
A region where roots absorb minerals
B.
A specialized region at the base of a leaf stalk where separation occurs
C.
A region where flowers produce pollen
D.
A region where seeds develop
Correct Answer:
A specialized region at the base of a leaf stalk where separation occurs
Explanation:
The abscission zone is a specialized layer of cells near the base of the petiole where the leaf separates from the stem.
4. How can abscisic acid contribute to leaf abscission?
A.
It can promote leaf shedding under certain stress conditions
B.
It always prevents leaves from falling
C.
It converts leaves directly into roots
D.
It stops all cell activity in the plant
Correct Answer:
It can promote leaf shedding under certain stress conditions
Explanation:
Abscisic acid may contribute to leaf abscission, particularly when the plant experiences stress such as drought.
5. Which condition is most likely to increase leaf abscission as a stress response?
A.
Adequate water supply
B.
Drought
C.
Normal mineral nutrition
D.
Favorable temperature
Correct Answer:
Drought
Explanation:
Drought can increase abscisic acid levels and may encourage leaf shedding, helping the plant reduce water loss.
6. What is the main advantage of leaf abscission during drought?
A.
It increases the leaf surface area
B.
It reduces water loss from the plant
C.
It increases flower production immediately
D.
It prevents root growth
Correct Answer:
It reduces water loss from the plant
Explanation:
By shedding leaves, a plant reduces the surface area through which water can be lost, helping it cope with drought.
7. Which hormone generally delays leaf abscission when present in sufficient amounts?
A.
Auxin
B.
Ethylene
C.
Abscisic acid
D.
Jasmonic acid
Correct Answer:
Auxin
Explanation:
Auxin produced by the leaf can help maintain the connection between the leaf and stem and delay abscission.
8. What happens to cells in the abscission zone during leaf shedding?
A.
They divide to form a new root
B.
Their cell walls are weakened by enzymes
C.
They become photosynthetic cells
D.
They produce pollen grains
Correct Answer:
Their cell walls are weakened by enzymes
Explanation:
During abscission, enzymes weaken the cell walls in the abscission zone, allowing the leaf to detach.
9. Which environmental condition can cause premature leaf abscission?
A.
Prolonged water deficiency
B.
Regular watering
C.
Balanced nutrition
D.
Moderate sunlight
Correct Answer:
Prolonged water deficiency
Explanation:
Prolonged water deficiency is a stress condition that can increase abscisic acid activity and lead to early leaf shedding.
10. What is the final visible result of leaf abscission?
A.
The leaf separates from the stem
B.
The leaf becomes a flower
C.
The stem changes into a root
D.
The leaf produces a seed immediately
Correct Answer:
The leaf separates from the stem
Explanation:
The final result of leaf abscission is the detachment and fall of the leaf from the plant.
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