biology : class11 Fruit Growth Enhancement : Functions, Effects, Applications : Gibberellin MCQ Questions and Answers
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Fruit Growth Enhancement
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MCQ Questions
1. In seedless table-grape production, the principal fruit-growth effect of gibberellic acid (GA3) applied after fruit set is to:
A.
Increase berry size by stimulating cell expansion
B.
Induce pollen germination and restore seed formation
C.
Prevent rachis elongation and compact the bunch
D.
Promote fruit abscission by accelerating ripening
Correct Answer:
Increase berry size by stimulating cell expansion
Explanation:
Post-set GA3 treatment enlarges grape berries mainly by promoting cell expansion, thereby increasing fruit size without requiring the formation of seeds.
2. A grower wants to obtain larger seedless grapes but applies gibberellic acid only after berries have completed most of their expansion. Which outcome is most likely?
A.
A strong increase in seed formation
B.
Limited fruit enlargement because the effective developmental window was missed
C.
Conversion of seedless berries into seeded berries
D.
Complete prevention of fruit ripening
Correct Answer:
Limited fruit enlargement because the effective developmental window was missed
Explanation:
GA3 is most effective for berry enlargement when applied during the appropriate early post-set growth stage; a late application generally produces a weaker size response.
3. Which application pattern best distinguishes the effects of gibberellin on grape fruit development?
A.
Pre-bloom treatment mainly enlarges berries, whereas post-set treatment mainly elongates the rachis
B.
Pre-bloom treatment can elongate the rachis, whereas post-set treatment can enlarge berries
C.
Both pre-bloom and post-set treatments exclusively increase seed number
D.
Pre-bloom treatment prevents fruit set, whereas post-set treatment induces flowering
Correct Answer:
Pre-bloom treatment can elongate the rachis, whereas post-set treatment can enlarge berries
Explanation:
In grapes, the developmental timing of GA3 application matters: pre-bloom treatment is associated with inflorescence or rachis elongation, while post-set treatment promotes berry enlargement.
4. A horticulturist applies gibberellin to an unfertilized ovary of a suitable fruit crop and obtains a fruit without seeds. This result is best interpreted as:
A.
Gibberellin-induced parthenocarpic fruit development
B.
Gibberellin-induced double fertilization
C.
Gibberellin-induced conversion of an ovary into a pollen grain
D.
Gibberellin-induced seed dormancy inside the ovary
Correct Answer:
Gibberellin-induced parthenocarpic fruit development
Explanation:
Gibberellin can substitute for some growth signals normally associated with fertilization, allowing fruit development without fertilization and producing seedless, parthenocarpic fruits.
5. Why can gibberellin treatment increase the marketable size of seedless grapes even though seed development is absent?
A.
It replaces every function of the missing embryo
B.
It stimulates fruit tissues, particularly through cell expansion, independently of seed growth
C.
It causes unfertilized ovules to divide into viable seeds
D.
It increases fruit size only by adding water from the soil directly into the berry
Correct Answer:
It stimulates fruit tissues, particularly through cell expansion, independently of seed growth
Explanation:
Seedless berries can enlarge after GA3 treatment because gibberellin acts on fruit tissues and promotes expansion, even when seeds are absent.
6. In a trial on grape clusters, treatment X is applied before flowering and treatment Y is applied shortly after fruit set. Which observation would most strongly indicate that both treatments acted as expected?
A.
X produces longer rachises, while Y produces larger berries
B.
X produces more seeds, while Y produces earlier pollen release
C.
X prevents flowering, while Y causes complete berry abortion
D.
X reduces rachis length, while Y eliminates cell expansion
Correct Answer:
X produces longer rachises, while Y produces larger berries
Explanation:
GA3 has stage-dependent effects in grapes: early treatment can elongate the cluster framework, whereas treatment after fruit set enhances berry growth.
7. A seedless fruit cultivar responds to gibberellin with increased fruit size, but a seeded cultivar shows little additional enlargement under the same treatment. Which explanation is most appropriate?
A.
The seedless cultivar may be more dependent on external growth stimulation because it lacks seed-derived growth signals
B.
Gibberellin can act only when seeds are present
C.
Seeds chemically destroy gibberellin before it reaches the fruit
D.
Seeded fruits cannot undergo cell expansion
Correct Answer:
The seedless cultivar may be more dependent on external growth stimulation because it lacks seed-derived growth signals
Explanation:
Developing seeds can naturally contribute growth-promoting signals. In seedless fruits, applied gibberellin may compensate for part of this deficiency and produce a stronger enlargement response.
8. A producer uses an excessively high concentration of GA3 on grape clusters to maximize berry size. Which result is a plausible horticultural disadvantage directly related to fruit growth enhancement?
A.
Overly loose clusters or misshapen berries that reduce market quality
B.
Guaranteed increase in seed number and uniform fertilization
C.
Complete conversion of berries into vegetative shoots
D.
Permanent prevention of all future fruit development
Correct Answer:
Overly loose clusters or misshapen berries that reduce market quality
Explanation:
Although GA3 can enlarge berries and elongate cluster structures, excessive dosage or unsuitable timing may produce undesirable berry shape or excessively loose bunches, reducing fruit quality.
9. Which experimental comparison would provide the strongest evidence that GA3 enhances berry growth rather than merely increasing the number of fruits?
A.
Compare average berry mass and diameter at harvest while keeping fruit number per cluster similar
B.
Compare leaf number without recording fruit characteristics
C.
Measure pollen viability only before treatment
D.
Record stem height without measuring berries
Correct Answer:
Compare average berry mass and diameter at harvest while keeping fruit number per cluster similar
Explanation:
Measuring berry mass and diameter under similar fruit-load conditions directly tests enlargement of individual fruits, which is the relevant fruit-growth effect of GA3.
10. A treatment causes fruit enlargement only when applied during the early stage of berry development, but has little effect after the berries begin ripening. What does this pattern most directly suggest about gibberellin use?
A.
Its fruit-size response is strongly dependent on developmental timing
B.
Its only role is to initiate pollen formation
C.
It functions exclusively by increasing seed viability
D.
It enlarges fruits by delaying fertilization until ripening
Correct Answer:
Its fruit-size response is strongly dependent on developmental timing
Explanation:
Gibberellin is most effective for fruit enlargement during active early growth, when cell division and especially cell expansion can still be strongly modified.
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