biology : class12 Hypocotyl Development : Dicot Embryo, Monocot Embryo, Embryonic Axis, Cotyledons : Embryo Development MCQ Questions and Answers
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Hypocotyl Development
MCQ questions and answers.
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MCQ Questions
1. During dicot embryo development, which embryonic region gives rise primarily to the hypocotyl?
A.
The embryonic axis between the cotyledonary node and the radicle
B.
The region above the cotyledonary node containing the plumule
C.
The terminal portion of each cotyledon
D.
The suspensor immediately adjacent to the basal cell
Correct Answer:
The embryonic axis between the cotyledonary node and the radicle
Explanation:
The hypocotyl develops from the lower part of the embryonic axis, extending from the cotyledonary node toward the radicle. It is distinct from the epicotyl, which lies above the cotyledons.
2. A developing dicot embryo shows marked elongation of the axis below the cotyledons while the cotyledons remain above the soil during germination. Which developmental pattern is most consistent with this observation?
A.
Hypogeal germination caused by elongation of the epicotyl
B.
Epigeal germination caused by elongation of the hypocotyl
C.
Hypogeal germination caused by elongation of the hypocotyl
D.
Epigeal germination caused exclusively by elongation of the radicle
Correct Answer:
Epigeal germination caused by elongation of the hypocotyl
Explanation:
In epigeal germination, elongation of the hypocotyl forms a hook and raises the cotyledons above the soil surface. The epicotyl is not the principal elongating region in this pattern.
3. What is the developmental significance of the hypocotyl hook commonly formed during dicot seedling emergence?
A.
It protects the plumule as the seedling pushes through the soil
B.
It prevents the radicle from becoming the primary root
C.
It converts the cotyledons directly into lateral roots
D.
It causes the endosperm to become part of the embryonic axis
Correct Answer:
It protects the plumule as the seedling pushes through the soil
Explanation:
The hypocotyl often bends into a hook during emergence. This curvature helps shield the delicate plumule and shoot apical region from mechanical damage as the seedling passes through the soil.
4. If the region of the embryonic axis between the cotyledons and radicle fails to elongate in a dicot seedling, which outcome is most likely during germination?
A.
The cotyledons will be lifted above the soil mainly by hypocotyl growth
B.
The cotyledons will remain near the seed while the shoot may emerge through epicotyl elongation
C.
The radicle will be transformed into the plumule
D.
The cotyledons will develop directly into the primary root system
Correct Answer:
The cotyledons will remain near the seed while the shoot may emerge through epicotyl elongation
Explanation:
Failure of hypocotyl elongation prevents the cotyledons from being raised above the soil. In such a situation, shoot emergence can occur through elongation of the epicotyl, characteristic of hypogeal development.
5. Which positional relationship correctly identifies the hypocotyl in a mature dicot embryo?
A.
It lies between the plumule and the cotyledonary node
B.
It lies between the cotyledonary node and the radicle
C.
It lies between the testa and the endosperm
D.
It lies between the cotyledon tips and the shoot apical meristem
Correct Answer:
It lies between the cotyledonary node and the radicle
Explanation:
The hypocotyl is the embryonic axis below the cotyledonary node and above the radicle. The portion above the cotyledons is the epicotyl, which bears the plumule.
6. A mutation specifically reduces cell elongation in the hypocotyl but does not eliminate the radicle or plumule. Which trait would be most directly affected in an epigeally germinating dicot?
A.
Elevation of the cotyledons above the soil
B.
Formation of the root cap
C.
Initiation of the cotyledonary node
D.
Production of pollen within the plumule
Correct Answer:
Elevation of the cotyledons above the soil
Explanation:
In epigeal germination, hypocotyl elongation is responsible for pulling the cotyledons above the soil surface. A defect in hypocotyl elongation would therefore directly impair this elevation.
7. Which comparison between hypocotyl development in epigeal and hypogeal dicot germination is most accurate?
A.
The hypocotyl is more strongly elongated in epigeal germination, whereas epicotyl elongation is more prominent in hypogeal germination
B.
The hypocotyl is absent in epigeal germination but present in hypogeal germination
C.
The hypocotyl elongates only after the primary root has ceased development in both patterns
D.
The hypocotyl always raises the cotyledons above the soil regardless of the germination pattern
Correct Answer:
The hypocotyl is more strongly elongated in epigeal germination, whereas epicotyl elongation is more prominent in hypogeal germination
Explanation:
Epigeal germination depends mainly on hypocotyl elongation to raise the cotyledons. In hypogeal germination, the hypocotyl remains relatively short and the epicotyl elongates to move the plumule upward.
8. Why is the hypocotyl considered part of the embryonic axis rather than part of either cotyledon in a dicot embryo?
A.
It is an axial segment connecting the cotyledonary region with the radicle
B.
It develops from the outer seed coat and surrounds both cotyledons
C.
It is formed exclusively by the fusion of the two cotyledons
D.
It originates from the endosperm and later becomes vascular tissue
Correct Answer:
It is an axial segment connecting the cotyledonary region with the radicle
Explanation:
The hypocotyl is defined by its axial position and continuity with the radicle and upper embryonic axis. Cotyledons are lateral embryonic structures attached at the cotyledonary node.
9. In a dicot embryo undergoing epigeal germination, which sequence best describes the role of the hypocotyl?
A.
It elongates, bends into a hook, emerges through the soil, and subsequently straightens to raise the cotyledons
B.
It differentiates into cotyledons, then develops the radicle after shoot emergence
C.
It remains completely inactive while the radicle lifts the cotyledons above the soil
D.
It elongates only after the plumule has fully expanded into mature leaves
Correct Answer:
It elongates, bends into a hook, emerges through the soil, and subsequently straightens to raise the cotyledons
Explanation:
The hypocotyl commonly elongates and forms a protective hook during epigeal emergence. Once above the soil, it straightens, thereby positioning the cotyledons above the surface.
10. A researcher marks the embryonic axis immediately below the cotyledonary node in a dicot embryo. After germination, the marked tissue is found below the cotyledons and above the primary root. What does this demonstrate?
A.
The marked tissue contributed to the hypocotyl
B.
The marked tissue contributed exclusively to the epicotyl
C.
The marked tissue became the seed coat
D.
The marked tissue formed the cotyledonary parenchyma only
Correct Answer:
The marked tissue contributed to the hypocotyl
Explanation:
The embryonic segment below the cotyledonary node develops as the hypocotyl. In the seedling, it remains positioned between the cotyledons and the primary root.
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