1. Which plant hormone is mainly associated with the drought response?
A.
Auxin
B.
Abscisic acid
C.
Gibberellin
D.
Cytokinin
Correct Answer:
Abscisic acid
Explanation:
During drought, abscisic acid levels increase and help the plant respond to water shortage.
2. What happens to the stomata of a plant during drought conditions?
A.
They open wider
B.
They remain permanently open
C.
They close
D.
They change into roots
Correct Answer:
They close
Explanation:
Abscisic acid promotes stomatal closure during drought, reducing water loss from the leaves.
3. Which process is reduced when stomata close during drought?
A.
Water loss by transpiration
B.
Seed formation
C.
Root growth only
D.
Mineral absorption completely
Correct Answer:
Water loss by transpiration
Explanation:
Closing the stomata reduces the escape of water vapour from the leaf through transpiration.
4. Where is abscisic acid mainly produced or increased during drought stress?
A.
In water-stressed plant tissues
B.
Only in flowers
C.
Only in fruits
D.
Only in the bark of old trees
Correct Answer:
In water-stressed plant tissues
Explanation:
Drought causes an increase in abscisic acid in affected plant tissues, helping the plant conserve water.
5. What is the main benefit of stomatal closure during drought?
A.
It increases water loss
B.
It conserves water
C.
It stops all plant growth permanently
D.
It increases leaf temperature intentionally
Correct Answer:
It conserves water
Explanation:
Stomatal closure limits transpiration and therefore helps the plant conserve water during drought.
6. A rise in abscisic acid during drought mainly signals the plant to do what?
A.
Reduce water loss
B.
Produce more flowers immediately
C.
Open stomata continuously
D.
Increase leaf expansion rapidly
Correct Answer:
Reduce water loss
Explanation:
Abscisic acid acts as a drought-stress signal that promotes responses such as stomatal closure to reduce water loss.
7. Which structure directly responds to abscisic acid by closing during drought?
A.
Root cap
B.
Guard cells
C.
Xylem vessels
D.
Pollen grains
Correct Answer:
Guard cells
Explanation:
Abscisic acid affects the guard cells surrounding stomata, causing them to close during water shortage.
8. Why is transpiration reduced during drought?
A.
Because stomata close
B.
Because roots stop existing
C.
Because chlorophyll disappears immediately
D.
Because leaves produce extra water
Correct Answer:
Because stomata close
Explanation:
Drought increases abscisic acid, which causes stomatal closure and lowers the loss of water through transpiration.
9. Which condition is most likely to increase abscisic acid production in a plant?
A.
Adequate water supply
B.
Water shortage in the soil
C.
Continuous flooding only
D.
High availability of minerals
Correct Answer:
Water shortage in the soil
Explanation:
A lack of water in the soil is a drought condition that stimulates abscisic acid accumulation and the plant's water-conserving response.
10. The drought response controlled by abscisic acid helps a plant maintain what?
A.
Water balance
B.
Flower colour
C.
Fruit sweetness only
D.
Seed size only
Correct Answer:
Water balance
Explanation:
By promoting stomatal closure and reducing transpiration, abscisic acid helps the plant maintain its water balance during drought.
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