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: Understanding the Concept:
The question is about plant embryogenesis and asks to identify the developmental stage at which the embryos of monocots and dicots, which have different final structures, are still morphologically similar.
Step 2: Detailed Explanation:
The development of the embryo from the zygote follows a series of predictable stages:

The zygote divides to form a two-celled proembryo, or a diad.
Further divisions lead to a four-celled stage (quadrant) and then an eight-celled stage (octant).
Continued cell division results in a spherical mass of cells, which is known as the globular stage.
Up to the globular stage, the embryo is radially symmetrical and looks essentially the same in both monocots and dicots. The key differentiation begins {after} this stage.

In dicots, two cotyledons (seed leaves) begin to form, giving the embryo a heart shape (heart stage), which then elongates into the torpedo stage.
In monocots, a single cotyledon develops, and the embryo typically becomes more cylindrical or scutiform, without passing through a distinct heart stage.
Step 3: Final Answer:
Since the major morphological divergence (development of one vs. two cotyledons) occurs after the globular stage, the early development is considered similar up to and including the globular stage.