Practice important
Floral Transition
MCQ questions and answers.
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MCQ Questions
1. In a rosette plant that requires long days for flowering, which effect of exogenous gibberellin most directly explains flowering under otherwise noninductive short-day conditions?
A.
Gibberellin promotes elongation and can substitute for the long-day floral stimulus in some species
B.
Gibberellin permanently converts every vegetative meristem into a floral meristem
C.
Gibberellin prevents bolting so that floral meristems remain protected in the rosette
D.
Gibberellin acts only by increasing seed germination before the plant becomes reproductive
Correct Answer:
Gibberellin promotes elongation and can substitute for the long-day floral stimulus in some species
Explanation:
In several long-day rosette plants, gibberellin promotes bolting and may induce floral transition even when the photoperiod is not normally inductive. This response is species-dependent rather than universal.
2. A dwarf rosette plant flowers after treatment with gibberellic acid, and its stem elongation is also restored. Which interpretation best links these two responses to floral transition?
A.
Gibberellin stimulates both bolting and, in responsive species, the switch from vegetative to reproductive development
B.
Gibberellin restores height but cannot influence the identity of the shoot apical meristem
C.
The restored height proves that flowering is caused only by increased water uptake
D.
Gibberellin induces flowering only after completely stopping cell division in the shoot apex
Correct Answer:
Gibberellin stimulates both bolting and, in responsive species, the switch from vegetative to reproductive development
Explanation:
Gibberellin commonly promotes internode elongation, producing bolting. In suitable plants, the same hormonal signal can promote floral transition, so the vegetative shoot changes toward reproductive development.
3. Which observation would provide the strongest evidence that gibberellin has promoted floral transition rather than merely increasing vegetative stem growth?
A.
The treated plants develop elongated internodes but retain exclusively vegetative shoot apices
B.
The treated plants show floral primordia at the shoot apex before visible flower opening
C.
The treated plants absorb more mineral nutrients from the soil
D.
The treated plants produce larger leaves without any change at the shoot apex
Correct Answer:
The treated plants show floral primordia at the shoot apex before visible flower opening
Explanation:
Floral transition is defined by the shoot apical meristem switching from vegetative to reproductive development. The appearance of floral primordia directly demonstrates this change, unlike increased elongation or leaf size.
4. In a gibberellin-responsive long-day plant, removal of the shoot apex before gibberellin application prevents flowering. What does this result most directly indicate?
A.
The shoot apex is the site whose developmental identity must change during floral transition
B.
Gibberellin can induce flowers only by acting on mature petals
C.
Gibberellin prevents flowering whenever roots remain attached to the plant
D.
Floral transition occurs exclusively in the root meristem before reaching the shoot
Correct Answer:
The shoot apex is the site whose developmental identity must change during floral transition
Explanation:
Floral transition involves conversion of the vegetative shoot apical meristem into a reproductive meristem. Removing this apex eliminates the developmental site on which gibberellin-mediated floral induction must act.
5. A mutant plant accumulates high levels of DELLA proteins and fails to flower after a gibberellin treatment that induces flowering in the wild type. Which conclusion is most consistent with this result?
A.
DELLA accumulation may block gibberellin signaling required for the floral transition
B.
DELLA proteins are sufficient to convert every vegetative meristem into a floral meristem
C.
Gibberellin must act independently of intracellular signaling during floral transition
D.
The mutant cannot respond because gibberellin functions only in seed dormancy release
Correct Answer:
DELLA accumulation may block gibberellin signaling required for the floral transition
Explanation:
Gibberellin signaling normally promotes DELLA degradation. Persistent DELLA proteins can repress gibberellin responses, thereby preventing the bolting and floral-transition effects that occur in responsive plants.
6. Why is it scientifically incorrect to conclude that gibberellin universally causes early flowering in all plant species?
A.
The floral response to gibberellin depends on species, developmental state, and interaction with environmental flowering signals
B.
Gibberellin is produced only in roots and therefore cannot reach the shoot apex
C.
Gibberellin always delays floral transition but accelerates fruit ripening
D.
Flowering time is determined exclusively by seed size and cannot be hormonally regulated
Correct Answer:
The floral response to gibberellin depends on species, developmental state, and interaction with environmental flowering signals
Explanation:
Gibberellin promotes floral transition in some plants, especially certain rosette and long-day species, but its effect is not universal. Genetic background, plant age, and photoperiodic conditions influence the response.
7. A long-day rosette plant is grown under short days. Which treatment would most directly test whether gibberellin can replace part of the photoperiodic requirement for floral transition?
A.
Apply gibberellin to one group under short days and compare flowering time with untreated plants under the same short days
B.
Apply water to one group under long days and compare leaf color with untreated plants under short days
C.
Remove all leaves from one group and measure root length under identical photoperiods
D.
Apply gibberellin to seeds and compare germination with flowering of untreated adult plants
Correct Answer:
Apply gibberellin to one group under short days and compare flowering time with untreated plants under the same short days
Explanation:
Keeping the short-day condition constant isolates the effect of gibberellin. Earlier floral transition in treated plants would support the ability of gibberellin to substitute for or bypass part of the normal photoperiodic requirement.
8. Which sequence best represents a gibberellin-associated developmental progression in a responsive rosette plant undergoing floral transition?
A.
Gibberellin response increases internode elongation, the shoot apex changes identity, and floral primordia form
B.
Gibberellin causes seed dormancy, suppresses stem elongation, and then produces vegetative leaves
C.
Gibberellin first forms petals directly, then converts flowers into roots and finally induces bolting
D.
Gibberellin destroys the shoot apex, prevents meristem activity, and produces flowers from mature leaves
Correct Answer:
Gibberellin response increases internode elongation, the shoot apex changes identity, and floral primordia form
Explanation:
In responsive rosette plants, gibberellin can promote bolting and accompany the conversion of the shoot apical meristem to a reproductive state, after which floral primordia are initiated.
9. A plant receives gibberellin and bolts rapidly, but microscopic examination shows that the shoot apex remains vegetative. Which conclusion is most appropriate?
A.
Gibberellin promoted vegetative elongation without yet causing floral transition
B.
Floral transition must already have occurred because bolting is identical to flowering
C.
The shoot apex is irrelevant because only internode length determines reproductive development
D.
Gibberellin must have inhibited all meristematic activity at the shoot apex
Explanation:
Bolting and floral transition can be associated but are not identical processes. Elongation of the stem demonstrates a growth response, whereas floral transition requires a change in the developmental identity of the shoot apex.
10. Which experimental result would most strongly support the idea that gibberellin acts during floral transition through the shoot apex rather than only through general whole-plant growth?
A.
Gibberellin applied near the shoot apex induces floral primordia, whereas an equivalent treatment restricted to a distant stem region does not
B.
Gibberellin increases root length equally in flowering and nonflowering plants
C.
Gibberellin increases leaf area without altering the developmental state of the apex
D.
Gibberellin delays flowering while increasing the dry mass of mature stems
Correct Answer:
Gibberellin applied near the shoot apex induces floral primordia, whereas an equivalent treatment restricted to a distant stem region does not
Explanation:
The shoot apical meristem is the site of floral transition. A localized response near the apex, shown by floral primordium formation, would support a direct or locally mediated role of gibberellin in changing apex identity.
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