Question

The part of the embryo axis between plumule and the cotyledonary node is
A. Hypocotyl
B. Epicotyl
C. Epicotyl and hypocotyl
D. Cotyledons and radicle

Answer 1

Hint: A seed consists of a small embryo plantlet. The developing embryonic axis has undeveloped leaves and embryonic shoot meristem at one end. Cotyledons are attached to the embryonic axis just below the plumule.

Complete answer:
Angiosperms and gymnosperms are also called spermatocytes or seed plants. A seed consists of an embryo which is the immature and developing sporophyte derived from the diploid zygote. The embryo is surrounded by the nutritive tissue called endosperm. Embryo and endosperm are enclosed within the protective seed coat.

The embryonic axis is composed of radicle, epicotyl, cotyledons, and hypocotyl. Cotyledons are the young seed leaves and are one or two in number. A typical dicotyledonous embryo consists of two cotyledons while the monocot embryo consists of a single cotyledon.

Radicle represents the immature root of the embryo. The hypocotyl is the transition region between root and stem and is present below the level of cotyledons. Hypocotyl terminates into the radicle. The epicotyl is the shoot apical meristem. Epicotyl is present above the level of cotyledons. The distal end of the epicotyl is called plumule or the stem tip. The plumule and the radicle are enclosed in the protective tissue sheaths called coleoptile and the coleorhiza, respectively.

Hence, the correct answer is option (B).

Note: In flowering plants, seeds represent the fertilized ovule. Seeds carry the developing embryo and are composed of seed coat, cotyledons and the embryonic axis. The two extreme ends of the embryonic axis serve as embryonic stem and embryonic root while cotyledons serve as young leaves and/or storage organs for the developing embryo.