1. Which plant hormone generally promotes seed dormancy in antagonism with gibberellins?
A.
Abscisic acid
B.
Gibberellin
C.
Auxin
D.
Cytokinin
Correct Answer:
Abscisic acid
Explanation:
Abscisic acid promotes seed dormancy, whereas gibberellins generally help break dormancy and promote germination.
2. Which hormone generally promotes the breaking of seed dormancy?
A.
Abscisic acid
B.
Gibberellin
C.
Ethylene
D.
Cytokinin
Correct Answer:
Gibberellin
Explanation:
Gibberellins antagonize abscisic acid by promoting the end of dormancy and initiating seed germination.
3. What is the main antagonistic effect of abscisic acid on gibberellin action during seed germination?
A.
It promotes the same growth response
B.
It inhibits germination promoted by gibberellins
C.
It increases gibberellin production in all seeds
D.
It changes gibberellins into auxins
Correct Answer:
It inhibits germination promoted by gibberellins
Explanation:
Abscisic acid maintains dormancy and suppresses germination, while gibberellins promote germination.
4. A high ratio of abscisic acid to gibberellin in a seed is most likely to result in:
A.
Seed dormancy
B.
Rapid seed germination
C.
Immediate fruit ripening
D.
Increased leaf expansion only
Correct Answer:
Seed dormancy
Explanation:
A higher influence of abscisic acid than gibberellin favors dormancy and prevents germination.
5. A high ratio of gibberellin to abscisic acid in a seed generally favors:
A.
Maintenance of dormancy
B.
Seed germination
C.
Stomatal closure
D.
Inhibition of embryo growth
Correct Answer:
Seed germination
Explanation:
Gibberellin dominance over abscisic acid favors breaking dormancy and starting germination.
6. Which pair correctly represents the antagonistic actions of abscisic acid and gibberellin?
A.
Abscisic acid promotes dormancy; gibberellin promotes germination
B.
Abscisic acid promotes germination; gibberellin promotes dormancy
C.
Both hormones always promote dormancy
D.
Both hormones always inhibit germination
Correct Answer:
Abscisic acid promotes dormancy; gibberellin promotes germination
Explanation:
The two hormones have opposite effects on seed dormancy: abscisic acid maintains it, while gibberellin helps end it.
7. During germination of a cereal grain, gibberellin helps oppose abscisic acid mainly by promoting the production of:
A.
Hydrolytic enzymes
B.
Dormancy proteins only
C.
Stomatal-closing pigments
D.
Cell-wall waxes
Correct Answer:
Hydrolytic enzymes
Explanation:
Gibberellin promotes hydrolytic enzymes such as amylase during germination, opposing the dormancy-maintaining effect of abscisic acid.
8. Which change would most likely break dormancy in a seed?
A.
Increased abscisic acid activity
B.
Increased gibberellin activity
C.
Decreased gibberellin activity
D.
Increased sensitivity to abscisic acid
Correct Answer:
Increased gibberellin activity
Explanation:
Increased gibberellin activity counteracts abscisic acid and promotes the breaking of seed dormancy.
9. Which change would most likely maintain dormancy in a seed?
A.
Increased gibberellin activity
B.
Increased abscisic acid activity
C.
Reduced abscisic acid activity
D.
Increased response to gibberellin
Correct Answer:
Increased abscisic acid activity
Explanation:
Abscisic acid maintains dormancy and opposes the germination-promoting action of gibberellins.
10. The antagonism between abscisic acid and gibberellins is most clearly observed in the regulation of:
A.
Seed dormancy and germination
B.
Flower colour only
C.
Pollen shape only
D.
Leaf arrangement only
Correct Answer:
Seed dormancy and germination
Explanation:
Abscisic acid and gibberellins act in opposite ways mainly during the control of seed dormancy and germination.
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