Question

In monocot embryos the radicle is produced by ……..
A. Terminal cell
B. Middle cell
C. Epiblast
D. Suspensor

Answer 1

Hint: Cotyledon are a type of embryonic leaf present in seed-bearing plants, and are generally one or more in number, which appears from a germinating seed. For the classification of flowering plants, the botanists used the number of cotyledons as a distinguishing feature. Species having one cotyledon are monocotyledons and the species having two cotyledons are dicotyledons.

Complete answer:
> The terminal cells help in the development of plant embryos and also generate the apical cells which are present at the apex region of the plant. Hence, option [A] Terminal cell is incorrect.

> The Middle cells are responsible for the production of radicals in a monocotyledonous seed.
The oospore or zygote elongates and then gets divided transversely for the formation of basal and terminal cells. The basal cell which is situated towards the micropylar end produces a vesicular suspensor cell, that is a large swollen structure. This can also function as haustorium. On the other hand, the terminal cell gets divided by the other transverse wall for forming two cells. A single cotyledon and plumule is formed after a series of divisions by the top cell. Further, the cotyledon known as scutellum rapidly grows and in turn pushes the plumule on one side. After many series of divisions, the middle cell forms radicle and hypocotyl. Hence, option [B] Middle cell is correct.

> The epiblast gives rise to the outer layer of the embryo known as blastula which develops into an ectoderm in gastrulation. Hence, option [C] is incorrect.

> The suspensor helps in pushing the embryo into the endosperm. Hence, option [D] is incorrect.

Hence, the correct answer is option (B).

Note: The total sum of changes which occur in the development of a mature embryo from an oospore or a zygote is known as embryogeny. Both the radicle and plumule get covered with sheaths that are developed from the scutellum known as coleorhiza and coleoptile respectively.