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Premature Flowering
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MCQ Questions
1. A genetically biennial rosette plant flowers prematurely after treatment with gibberellic acid (GA3) without experiencing winter. Which interpretation best explains this response?
A.
GA3 substituted for the cold-induced phase required before flowering
B.
GA3 permanently converted the plant into an annual species
C.
GA3 prevented the formation of the shoot apical meristem
D.
GA3 directly destroyed the plant's photoreceptor system
Correct Answer:
GA3 substituted for the cold-induced phase required before flowering
Explanation:
In some biennial or rosette plants, exogenous gibberellin can induce premature flowering and bolting, partly replacing the requirement for vernalization or winter exposure.
2. A rosette plant remains vegetative under non-inductive conditions but produces a rapidly elongated flowering stalk soon after GA3 application. Which effect of gibberellin is most directly responsible for this premature flowering phenotype?
A.
Induction of bolting that elevates the shoot apex into a flowering state
B.
Suppression of internode elongation that concentrates leaves at the base
C.
Inhibition of floral meristem formation until seed maturation
D.
Acceleration of root thickening that signals the onset of dormancy
Correct Answer:
Induction of bolting that elevates the shoot apex into a flowering state
Explanation:
Gibberellin can stimulate bolting in rosette plants. The associated internode elongation is often linked with transition from vegetative growth to premature flowering.
3. Two genetically similar rosette plants receive identical GA3 doses, but only the plants with an actively growing shoot apex flower prematurely. Which conclusion is most appropriate?
A.
Gibberellin responsiveness depends partly on the developmental state of the shoot apex
B.
Gibberellin can induce flowering only after seed dispersal
C.
Gibberellin acts exclusively through root tissues during premature flowering
D.
Gibberellin prevents floral transition whenever the shoot apex is active
Correct Answer:
Gibberellin responsiveness depends partly on the developmental state of the shoot apex
Explanation:
Premature flowering induced by gibberellin is not determined only by the hormone dose; the developmental condition and competence of the shoot apex also influence the response.
4. A biennial crop is treated with GA3 before its normal winter period and flowers in the same growing season. What has most likely occurred?
A.
The normal juvenile or vernalization-associated delay in flowering was shortened
B.
The plant's chromosomes were doubled, causing immediate reproductive maturity
C.
The floral organs were formed directly from mature root tissues
D.
The plant was prevented from undergoing the vegetative phase entirely
Correct Answer:
The normal juvenile or vernalization-associated delay in flowering was shortened
Explanation:
GA3 can reduce the time to flowering in certain biennial plants by promoting premature floral transition, thereby shortening the normally prolonged vegetative period.
5. Which experimental result would provide the strongest evidence that GA3 caused premature flowering rather than merely increasing vegetative growth?
A.
GA3-treated plants produce flowers earlier while untreated plants remain vegetative for the same observation period
B.
GA3-treated plants develop larger roots but do not differ in flowering time
C.
GA3-treated plants retain the same flowering time but have heavier leaves
D.
GA3-treated plants show greater water uptake without any change in shoot development
Correct Answer:
GA3-treated plants produce flowers earlier while untreated plants remain vegetative for the same observation period
Explanation:
Premature flowering is demonstrated by an earlier reproductive transition relative to an untreated control, not merely by increased biomass or water uptake.
6. A researcher applies GA3 to a biennial plant and observes bolting but no flowers. Which conclusion is most scientifically justified?
A.
GA3 promoted stem elongation, but flowering may still require another environmental or developmental condition
B.
GA3 necessarily prevents flowering whenever it induces bolting
C.
Bolting proves that the plant has completed every requirement for floral induction
D.
The observation demonstrates that gibberellin acts only by inhibiting stem growth
Correct Answer:
GA3 promoted stem elongation, but flowering may still require another environmental or developmental condition
Explanation:
Bolting and flowering are related but distinguishable responses. Gibberellin may induce elongation without being sufficient to complete floral induction in every species or condition.
7. Why is gibberellin particularly effective in producing premature flowering in many rosette plants?
A.
It can stimulate internode elongation and overcome part of the vegetative restraint associated with the rosette habit
B.
It converts every leaf directly into a floral organ without affecting the shoot
C.
It permanently eliminates the shoot apical meristem before flowering begins
D.
It suppresses all cell division, forcing the plant to reproduce immediately
Correct Answer:
It can stimulate internode elongation and overcome part of the vegetative restraint associated with the rosette habit
Explanation:
The rosette habit involves very short internodes. Gibberellin promotes internode elongation, often causing bolting and facilitating an earlier transition to flowering.
8. A plant flowers prematurely after GA3 treatment only when exposed to a suitable photoperiod. What does this result indicate?
A.
Gibberellin can interact with photoperiodic control rather than universally replacing light requirements
B.
Gibberellin completely abolishes the plant's ability to perceive day length
C.
Photoperiod has no role in flowering once gibberellin is present
D.
The observed flowering must be unrelated to the gibberellin treatment
Correct Answer:
Gibberellin can interact with photoperiodic control rather than universally replacing light requirements
Explanation:
Gibberellin may promote premature flowering in some plants, but its effect can remain dependent on photoperiod and the plant's flowering pathway.
9. Which treatment would best test whether GA3 is replacing a seasonal requirement for flowering in a biennial plant?
A.
Compare untreated and GA3-treated plants kept without winter exposure, while recording the time of flowering
B.
Compare plants receiving different fertilizer concentrations after flowering has ended
C.
Measure root respiration only in plants that have already produced seeds
D.
Compare leaf color in plants grown under identical conditions after seed dispersal
Correct Answer:
Compare untreated and GA3-treated plants kept without winter exposure, while recording the time of flowering
Explanation:
Keeping both groups without winter exposure and comparing flowering time directly tests whether GA3 can bypass or shorten the seasonal requirement associated with delayed flowering.
10. A premature-flowering response to GA3 disappears when the shoot apex is removed before treatment. Which inference is most consistent with this observation?
A.
GA3-induced flowering requires a responsive shoot apex capable of undergoing floral transition
B.
GA3 induces flowers exclusively in roots and therefore cannot act after root removal
C.
The shoot apex normally prevents flowering by destroying all gibberellin molecules
D.
GA3 causes premature flowering only by enlarging mature leaves
Correct Answer:
GA3-induced flowering requires a responsive shoot apex capable of undergoing floral transition
Explanation:
The shoot apex is the site where the vegetative-to-reproductive transition occurs. Removing it eliminates the tissue that must respond for GA3-induced premature flowering.
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