Practice important
Seed Dormancy Induction
MCQ questions and answers.
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MCQ Questions
1. Which hormonal change most directly induces primary seed dormancy during maturation?
A.
A sustained increase in abscisic acid concentration in the developing seed
B.
A sustained increase in gibberellin concentration in the developing seed
C.
A rapid increase in auxin concentration after seed shedding
D.
A decrease in ethylene sensitivity of the mature embryo
Correct Answer:
A sustained increase in abscisic acid concentration in the developing seed
Explanation:
Abscisic acid accumulates during seed maturation and induces dormancy by suppressing premature embryo growth and preventing germination before the seed is fully mature.
2. A developing seed has normal embryo viability but fails to germinate even when supplied with water, oxygen, and a suitable temperature. Which explanation best supports ABA-induced dormancy?
A.
The embryo has permanently lost its ability to divide
B.
High ABA maintains inhibition of embryo growth and counteracts germination-promoting signals
C.
The seed lacks oxygen because imbibition has completely stopped
D.
The seed coat has converted all stored food into structural cellulose
Correct Answer:
High ABA maintains inhibition of embryo growth and counteracts germination-promoting signals
Explanation:
ABA-induced dormancy can persist despite favorable external conditions because ABA inhibits embryo growth and antagonizes the hormonal processes required for germination.
3. Which experimental result would provide the strongest evidence that ABA is inducing seed dormancy rather than merely maintaining seed viability?
A.
Exogenous ABA prevents germination of viable seeds, whereas an ABA-insensitive mutant germinates under the same conditions
B.
Seeds germinate only after their seed coats are mechanically removed, regardless of ABA treatment
C.
Seeds with damaged embryos fail to germinate after treatment with water
D.
Seeds become heavier as they absorb water during imbibition
Correct Answer:
Exogenous ABA prevents germination of viable seeds, whereas an ABA-insensitive mutant germinates under the same conditions
Explanation:
If ABA suppresses germination in normal viable seeds but not in ABA-insensitive seeds, the result directly links ABA perception or signaling with dormancy induction.
4. During seed maturation, which combination most strongly favors induction of dormancy?
A.
High ABA activity, reduced embryo growth, and accumulation of protective storage products
B.
High gibberellin activity, rapid embryo expansion, and immediate reserve mobilization
C.
Low ABA activity, increased water uptake, and activation of hydrolytic enzymes
D.
High ethylene activity, rapid radicle emergence, and degradation of storage reserves
Correct Answer:
High ABA activity, reduced embryo growth, and accumulation of protective storage products
Explanation:
Dormancy is promoted during maturation by ABA-dependent suppression of embryo growth together with maturation-associated protection and storage processes.
5. Why does ABA accumulation during seed development help prevent vivipary in many plants?
A.
It induces premature conversion of the embryo into a root
B.
It inhibits premature germination while the seed is still attached to the parent plant
C.
It permanently destroys the embryo before fruit maturation
D.
It increases water entry into the embryo and accelerates radicle growth
Correct Answer:
It inhibits premature germination while the seed is still attached to the parent plant
Explanation:
ABA-induced dormancy prevents embryos from germinating precociously inside the fruit or on the parent plant, a phenomenon known as vivipary.
6. A mutation causes a developing seed to synthesize very little ABA, while its embryo remains viable. Which phenotype is most likely?
A.
Enhanced primary dormancy and delayed germination under favorable conditions
B.
Reduced primary dormancy and increased precocious germination during seed development
C.
Complete inability of the embryo to absorb water after dispersal
D.
Permanent activation of dormancy even after all ABA is removed
Correct Answer:
Reduced primary dormancy and increased precocious germination during seed development
Explanation:
Lower ABA synthesis weakens the hormonal signal that establishes primary dormancy, increasing the chance of premature germination during seed maturation.
7. Which relationship between ABA and gibberellin is most relevant to the induction of seed dormancy?
A.
ABA promotes germination while gibberellin suppresses embryo growth
B.
ABA and gibberellin always act independently during seed maturation
C.
ABA favors dormancy by opposing the germination-promoting effects of gibberellin
D.
Gibberellin induces dormancy by increasing ABA breakdown in the embryo
Correct Answer:
ABA favors dormancy by opposing the germination-promoting effects of gibberellin
Explanation:
Seed dormancy induction depends partly on the balance between ABA and gibberellin; ABA suppresses processes promoted by gibberellin, including embryo growth and germination.
8. A seed variety accumulates unusually high ABA during late embryogenesis. Which observation would most specifically indicate that ABA has induced dormancy?
A.
The mature seed remains viable but does not resume embryo growth immediately after imbibition
B.
The mature seed has no embryo and contains only dead storage tissue
C.
The seed germinates rapidly as soon as it contacts water
D.
The seed loses all stored carbohydrates before dispersal
Correct Answer:
The mature seed remains viable but does not resume embryo growth immediately after imbibition
Explanation:
A dormant seed is alive and potentially capable of germination, but ABA-induced inhibition prevents immediate embryo growth after water uptake.
9. Which intervention would most directly weaken ABA-mediated induction of seed dormancy during seed maturation?
A.
Increasing ABA synthesis in the developing embryo
B.
Enhancing ABA sensitivity in embryonic tissues
C.
Reducing ABA synthesis or blocking ABA perception in the developing seed
D.
Increasing the activity of ABA-responsive dormancy genes
Correct Answer:
Reducing ABA synthesis or blocking ABA perception in the developing seed
Explanation:
ABA must be produced and perceived to establish dormancy. Reducing its synthesis or blocking its signaling weakens the induction of dormancy.
10. Which statement best distinguishes ABA-induced seed dormancy from loss of seed viability?
A.
Dormancy is reversible inhibition of germination in a living seed, whereas loss of viability involves embryo death or irreversible damage
B.
Dormancy occurs only in dead seeds, whereas viability occurs only in dry seeds
C.
Dormancy always results from absence of water, whereas loss of viability always results from excess oxygen
D.
Dormant seeds cannot resume growth under any conditions, whereas nonviable seeds germinate rapidly
Correct Answer:
Dormancy is reversible inhibition of germination in a living seed, whereas loss of viability involves embryo death or irreversible damage
Explanation:
ABA-induced dormancy suppresses germination without killing the embryo. A viable dormant seed can later germinate when dormancy is relieved, unlike a nonviable seed.
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