Question

The portion of the embryonal axis between plumule (future shoot) and cotyledons is called
a. Hypocotyl
b. Epicotyl
c. Coleorhiza
d. Coleoptile

Answer 1

Cotyledon is a significant part of the embryo within the seed of a plant. It is basically the embryonic leaf in a seed-bearing plant from which the very first leaves grow or appear.

Complete Answer:
The seed has an outer covering called the seed coat which encloses an embryo that is differentiated into plumule, radicle, and cotyledons. Plumule is the upper terminal part of the embryo which elongates and develops into the future shoot. The lower end of the embryo is the radicle, which develops into a future root.

- Hypocotyl is the transition zone between the shoot and root and the radicle. It is the part of the stem of an embryo plant beneath the stalks of the seed leaves or cotyledons and directly above the root.
- Epicotyl is the part of the embryonic axis between the plumule and point of attachment of cotyledons. It is the region of an embryo or seedling stem above the cotyledon. In most plants, the epicotyl eventually develops into the leaves of the plant.
- Coleorhiza is a sheath-like structure found in a monocotyledon plant seed that acts as a protective covering enclosing the radicle.
- Coleoptile can be defined as the pointed protective sheath covering the emerging shoot in monocotyledons e.g., grasses, in which few leaf primordia and shoot apex of monocot embryo remain enclosed. Coleoptiles have two vascular bundles, one on either side.

Thus, the correct option is b) Epicotyl.

Note: The difference between epicotyl and hypocotyl is that the latter is a part of the embryonal axis which is present above the cotyledons in a dicot embryo. Whereas, hypocotyl is the part of the embryonal axis which is present below the cotyledon in a dicot embryo. Please do not get confused between both the terms.