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Seed Germination Stimulation
MCQ questions and answers.
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MCQ Questions
1. In a germinating cereal grain, which sequence best explains how gibberellin stimulates the mobilization of stored starch?
A.
Gibberellin from the embryo induces aleurone cells to synthesize hydrolytic enzymes, including alpha-amylase, which acts on endosperm starch
B.
Gibberellin from the endosperm directly converts starch into glucose without requiring enzyme synthesis
C.
Gibberellin suppresses aleurone activity so that the embryo obtains energy only from stored lipids
D.
Gibberellin causes the seed coat to synthesize chlorophyll before starch breakdown begins
Correct Answer:
Gibberellin from the embryo induces aleurone cells to synthesize hydrolytic enzymes, including alpha-amylase, which acts on endosperm starch
Explanation:
During cereal seed germination, gibberellin produced by the embryo diffuses to the aleurone layer and stimulates synthesis and secretion of alpha-amylase and other hydrolytic enzymes. These enzymes mobilize endosperm reserves for the growing embryo.
2. A cereal seed is supplied with gibberellin, but its aleurone layer has been experimentally removed. Which outcome is most likely under otherwise suitable germination conditions?
A.
Starch mobilization will be greatly reduced because the major gibberellin-responsive enzyme-producing tissue is absent
B.
Starch mobilization will increase because gibberellin acts directly on starch granules
C.
The embryo will produce chlorophyll immediately and compensate completely for the missing aleurone layer
D.
Gibberellin will prevent water uptake, thereby stopping only protein mobilization
Correct Answer:
Starch mobilization will be greatly reduced because the major gibberellin-responsive enzyme-producing tissue is absent
Explanation:
The aleurone layer is a principal site where gibberellin induces alpha-amylase and related hydrolytic enzymes. Removing it substantially impairs enzymatic mobilization of endosperm starch even when gibberellin is supplied.
3. Which experimental observation would provide the strongest evidence that gibberellin promotes cereal seed germination through aleurone-cell activation?
A.
Gibberellin-treated aleurone tissue shows increased alpha-amylase secretion and the surrounding starch decreases more rapidly
B.
Gibberellin-treated dry seeds become heavier before absorbing water
C.
Gibberellin-treated seeds produce flowers before radicle emergence
D.
Gibberellin-treated embryos lose their ability to use soluble sugars
Correct Answer:
Gibberellin-treated aleurone tissue shows increased alpha-amylase secretion and the surrounding starch decreases more rapidly
Explanation:
An increase in alpha-amylase secretion followed by faster starch disappearance directly links gibberellin treatment with hydrolytic enzyme production and reserve mobilization, a central mechanism of its germination-promoting effect.
4. A mutant cereal embryo produces very little gibberellin but responds normally when gibberellin is supplied externally. Which interpretation is most appropriate?
A.
The mutation primarily affects gibberellin production rather than the ability of target tissues to respond to gibberellin
B.
The mutation affects alpha-amylase structure, while gibberellin production remains normal
C.
The mutation prevents water absorption, but external gibberellin restores imbibition directly
D.
The mutation causes the endosperm to contain no stored starch, although enzyme induction remains unaffected
Correct Answer:
The mutation primarily affects gibberellin production rather than the ability of target tissues to respond to gibberellin
Explanation:
If external gibberellin restores germination-related enzyme induction, the aleurone and its signaling machinery are functional. The defect is therefore most consistent with inadequate endogenous gibberellin production by the embryo.
5. Why does gibberellin treatment generally improve the early growth of an embryo in a cereal grain?
A.
It promotes hydrolysis of endosperm reserves, increasing the supply of soluble nutrients to the developing embryo
B.
It converts the embryo into a photosynthetic organ before it emerges from the soil
C.
It increases the amount of starch stored in the endosperm without changing its availability
D.
It replaces the need for oxygen by allowing the embryo to respire only anaerobically
Correct Answer:
It promotes hydrolysis of endosperm reserves, increasing the supply of soluble nutrients to the developing embryo
Explanation:
Gibberellin stimulates production of enzymes that break down starch and other stored reserves. The resulting soluble sugars and nutrients support respiration and growth of the embryo during the early stages of germination.
6. In an experiment, one group of barley grains receives gibberellin after imbibition, while another receives only water. Which result most specifically indicates gibberellin-stimulated germination?
A.
The gibberellin-treated grains show earlier alpha-amylase activity and faster production of soluble sugars
B.
The water-treated grains show greater seed-coat lignification before radicle emergence
C.
The gibberellin-treated grains show reduced oxygen uptake because reserve breakdown is inhibited
D.
The water-treated grains produce more hydrolytic enzymes because gibberellin suppresses aleurone cells
Correct Answer:
The gibberellin-treated grains show earlier alpha-amylase activity and faster production of soluble sugars
Explanation:
Gibberellin accelerates the induction of alpha-amylase in the aleurone layer. Enhanced starch hydrolysis produces soluble sugars that can be detected before or during accelerated embryo growth.
7. A seed contains abundant starch but has impaired gibberellin signaling in its aleurone cells. Which process would be most directly disrupted?
A.
Induction and secretion of alpha-amylase required for endosperm starch mobilization
B.
Absorption of water by the seed coat during imbibition
C.
Replication of chloroplast DNA in fully expanded leaves
D.
Formation of pollen grains in the mature plant
Correct Answer:
Induction and secretion of alpha-amylase required for endosperm starch mobilization
Explanation:
Aleurone cells must perceive and respond to gibberellin to produce and release alpha-amylase. Impaired signaling therefore blocks a key step in converting stored starch into usable sugars during germination.
8. Which comparison best distinguishes the effect of gibberellin from simple water uptake during cereal seed germination?
A.
Water initiates hydration and metabolic reactivation, whereas gibberellin specifically promotes hydrolytic enzyme production and reserve mobilization
B.
Water induces alpha-amylase directly, whereas gibberellin only permits the seed coat to absorb more water
C.
Water and gibberellin perform identical functions, differing only in their chemical composition
D.
Gibberellin initiates imbibition, whereas water directly hydrolyzes endosperm starch into sugars
Correct Answer:
Water initiates hydration and metabolic reactivation, whereas gibberellin specifically promotes hydrolytic enzyme production and reserve mobilization
Explanation:
Imbibition is driven by water entry and is essential for reactivating metabolism. Gibberellin then functions as a hormonal signal that promotes enzyme production, especially in the aleurone layer, enabling mobilization of stored reserves.
9. A researcher applies gibberellin to the embryo side of an intact cereal grain and observes increased alpha-amylase in the aleurone layer. What does this demonstrate most directly?
A.
The embryo can act as a source of a diffusible signal that regulates reserve mobilization in surrounding tissues
B.
The aleurone layer produces gibberellin independently of the embryo and does not require hormonal signaling
C.
Alpha-amylase is synthesized by the starch granules and released after direct contact with the embryo
D.
Gibberellin functions only as a nutrient and is incorporated unchanged into alpha-amylase
Correct Answer:
The embryo can act as a source of a diffusible signal that regulates reserve mobilization in surrounding tissues
Explanation:
In cereal grains, embryo-derived gibberellin acts as a signal to the aleurone layer. The resulting alpha-amylase production shows that hormonal communication coordinates endosperm reserve mobilization with embryo development.
10. If gibberellin is applied to a cereal seed in which alpha-amylase synthesis is chemically blocked, which outcome is most likely?
A.
Germination-related mobilization of starch will remain strongly limited despite the presence of gibberellin
B.
Gibberellin will convert the stored starch into soluble sugar without any enzyme
C.
The embryo will use endosperm starch directly without hydrolysis
D.
The seed will germinate normally because gibberellin replaces all hydrolytic enzymes
Correct Answer:
Germination-related mobilization of starch will remain strongly limited despite the presence of gibberellin
Explanation:
Gibberellin stimulates the synthesis of hydrolytic enzymes but does not itself hydrolyze starch. Blocking alpha-amylase formation therefore prevents efficient conversion of endosperm starch into soluble nutrients needed by the embryo.
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