Explanation:
The embryonal axis of a mature dicot embryo has the plumule at its upper end, followed by the epicotyl and hypocotyl, with the radicle at the lower end.
2. Which feature most reliably distinguishes the cotyledons of a mature dicot embryo from the embryonal axis?
A.
They contain the radicle and root cap.
B.
They are the two embryonic leaves attached laterally to the axis.
C.
They form the apical meristem of the future shoot.
D.
They occupy the region between the hypocotyl and radicle.
Correct Answer:
They are the two embryonic leaves attached laterally to the axis.
Explanation:
A mature dicot embryo characteristically possesses two cotyledons, which are embryonic leaves attached laterally to the embryonal axis.
3. If the region between the cotyledonary node and the radicle is experimentally removed from a mature dicot embryo, which embryonic structure has been removed?
A.
Epicotyl
B.
Plumule
C.
Hypocotyl
D.
Cotyledonary node
Correct Answer:
Hypocotyl
Explanation:
The hypocotyl is the portion of the embryonal axis extending from the cotyledonary node toward the radicle.
4. In a mature dicot embryo, the plumule is best identified as the structure that contains or gives rise to the:
A.
Primary root and its root cap
B.
Shoot apical meristem and young leaves
C.
Two food-storage cotyledons only
D.
Region of the axis immediately below the cotyledons
Correct Answer:
Shoot apical meristem and young leaves
Explanation:
The plumule is the embryonic shoot present at the upper end of the embryonal axis and includes the shoot apical meristem with developing leaves.
5. Which statement correctly describes the positional relationship of the epicotyl in a mature dicot embryo?
A.
It lies between the radicle and the root cap.
B.
It is the part of the axis below the cotyledonary node.
C.
It lies between the cotyledonary node and the plumule.
D.
It is the portion of each cotyledon surrounding the plumule.
Correct Answer:
It lies between the cotyledonary node and the plumule.
Explanation:
The epicotyl is the upper part of the embryonal axis, extending from the cotyledonary node to the plumule.
6. A mature dicot embryo is sectioned so that both lateral appendages attached to the embryonal axis are removed, while the axis remains intact. Which structures were removed?
A.
The two cotyledons
B.
The plumule and radicle
C.
The epicotyl and hypocotyl
D.
The radicle and root cap
Correct Answer:
The two cotyledons
Explanation:
The two lateral appendages of a mature dicot embryo are its paired cotyledons, attached at the cotyledonary node.
7. Which combination includes only structures belonging to the embryonal axis of a mature dicot embryo?
A.
Cotyledons, plumule, and hypocotyl
B.
Plumule, epicotyl, hypocotyl, and radicle
C.
Cotyledons, endosperm, and radicle
D.
Cotyledons, testa, and plumule
Correct Answer:
Plumule, epicotyl, hypocotyl, and radicle
Explanation:
The embryonal axis comprises the plumule, epicotyl, hypocotyl, and radicle; the cotyledons are lateral embryonic leaves rather than parts of the axis.
8. In a mature dicot embryo, the cotyledonary node is most accurately defined as the region:
A.
Where the radicle terminates in the root cap
B.
From which the plumule develops directly without an intervening axis
C.
At which the two cotyledons are attached to the embryonal axis
D.
That separates the radicle from the root cap
Correct Answer:
At which the two cotyledons are attached to the embryonal axis
Explanation:
The cotyledonary node is the point on the embryonal axis where the paired cotyledons are attached; it separates the epicotyl above from the hypocotyl below.
9. Which alteration would preserve the defining dicot condition in a mature embryo while changing the identity of an individual embryonic organ?
A.
Replacing two cotyledons with one cotyledon
B.
Replacing the radicle with a second plumule
C.
Changing the cotyledons from storage organs to photosynthetic organs
D.
Removing the embryonal axis while retaining the cotyledons
Correct Answer:
Changing the cotyledons from storage organs to photosynthetic organs
Explanation:
A mature dicot embryo is defined by its paired cotyledons, not by whether those cotyledons primarily store food or become photosynthetic after emergence.
10. When the radicle of a mature dicot embryo is identified in relation to the embryonal axis, which description is correct?
A.
It is the terminal embryonic root at the lower end of the axis.
B.
It is the terminal embryonic shoot at the upper end of the axis.
C.
It is the portion between the cotyledons and the plumule.
D.
It is the lateral embryonic leaf attached at the cotyledonary node.
Correct Answer:
It is the terminal embryonic root at the lower end of the axis.
Explanation:
The radicle forms the lower terminal region of the embryonal axis in a mature dicot embryo and gives rise to the primary root.
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Mature Dicot Embryo
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