1. Which plant hormone helps conserve water during drought conditions by causing stomatal closure?
A.
Auxin
B.
Abscisic acid
C.
Gibberellin
D.
Cytokinin
Correct Answer:
Abscisic acid
Explanation:
Abscisic acid promotes the closure of stomata during water stress, reducing water loss from the leaves.
2. What is the main effect of abscisic acid on stomata during water shortage?
A.
It causes them to open widely
B.
It causes them to close
C.
It increases their number
D.
It changes them into root hairs
Correct Answer:
It causes them to close
Explanation:
Stomatal closure reduces the escape of water vapour from leaves and helps the plant conserve water.
3. Water loss from leaves mainly occurs through which structures that are regulated by abscisic acid?
A.
Stomata
B.
Root caps
C.
Xylem vessels
D.
Seed coats
Correct Answer:
Stomata
Explanation:
Stomata are small pores in leaves through which water vapour is lost. Abscisic acid helps close them during water stress.
4. Abscisic acid helps a plant survive drought primarily by reducing which process?
A.
Photosynthesis in roots
B.
Transpiration
C.
Seed formation
D.
Mineral absorption
Correct Answer:
Transpiration
Explanation:
By closing stomata, abscisic acid decreases transpiration, which is the loss of water vapour from plant surfaces.
5. Under drought conditions, where does abscisic acid commonly promote water-conserving action?
A.
In the stomatal guard cells
B.
In the petals only
C.
In the pollen grains only
D.
In the fruit wall only
Correct Answer:
In the stomatal guard cells
Explanation:
Abscisic acid acts on guard cells to bring about stomatal closure, thereby limiting water loss.
6. A plant treated with abscisic acid is most likely to show which response during dry conditions?
A.
Reduced water loss
B.
Increased stomatal opening
C.
Increased leaf water loss
D.
Faster evaporation from leaves
Correct Answer:
Reduced water loss
Explanation:
Abscisic acid closes stomata, so less water vapour escapes from the leaves.
7. Why is abscisic acid often called a stress hormone in relation to water conservation?
A.
It increases water loss during drought
B.
It helps plants respond to water deficiency
C.
It prevents roots from absorbing water
D.
It permanently stops plant growth
Correct Answer:
It helps plants respond to water deficiency
Explanation:
Abscisic acid is produced or accumulates during water stress and helps conserve water by inducing stomatal closure.
8. What happens to the rate of transpiration when abscisic acid causes stomata to close?
A.
It decreases
B.
It increases greatly
C.
It remains permanently unchanged
D.
It changes into respiration
Correct Answer:
It decreases
Explanation:
Closed stomata restrict the movement of water vapour out of the leaf, lowering transpiration.
9. Which environmental condition is most likely to stimulate the water-conserving action of abscisic acid?
A.
Water deficiency
B.
Excess rainfall
C.
High soil moisture
D.
Continuous flooding only
Correct Answer:
Water deficiency
Explanation:
Water deficiency is a stress condition that promotes abscisic acid action, including stomatal closure to conserve water.
10. Closing stomata with the help of abscisic acid benefits a plant by preserving which substance?
A.
Water
B.
Carbon dioxide only
C.
Oxygen in the soil
D.
Chlorophyll in the roots
Correct Answer:
Water
Explanation:
Stomatal closure limits water vapour loss and therefore helps the plant retain water during dry conditions.
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