Question

The early development of monocot and dicot embryo is similar up to which stage?

• A. Octant stage
• B. Diad stage
• C. Globular stage
• D. Quadrant stage

Hint:

Think of the globular stage as the last point of "common design" in embryo development. After this spherical stage, the plant commits to its blueprint: two growing points for cotyledons in dicots (leading to the heart shape) or one in monocots.

Answer 1

The Correct Option is C

Step 1: Concept Overview:
This question concerns plant embryogenesis. It asks at which developmental stage monocot and dicot embryos, despite their different final forms, share similar morphology.
Step 2: Detailed Explanation:
Embryo development from the zygote progresses through these stages:

Zygote division forms a two-celled proembryo, or diad.
Further divisions create a four-celled (quadrant) and then an eight-celled (octant) stage.
Subsequent cell division results in a spherical cell mass: the globular stage.
Until the globular stage, embryos exhibit radial symmetry and are nearly identical in monocots and dicots. Differentiation begins after this point.

In dicots, two cotyledons (seed leaves) develop, giving the embryo a heart shape (heart stage), which then elongates to the torpedo stage.
In monocots, a single cotyledon develops, and the embryo becomes cylindrical or scutiform, bypassing a distinct heart stage.
Step 3: Final Answer:
Because the primary morphological difference (one vs. two cotyledons) arises after the globular stage, early development is similar up to and including the globular stage.