Question

Select the correct sequence of events for plant somatic embryogenesis:
A. Production of torpedo stage embryos
B. Initiation of embryogenic callus
C. Formation of globular embryos
D. Production of green cotyledonary stage embryos
Choose the correct answer from the options given below:

• A. B, C, A, D
• B. A, D, C, B
• C. B, A, D, C
• D. D, C, B, A

Hint:

The standard shape sequence is always: Globular $\rightarrow$ Heart $\rightarrow$ Torpedo $\rightarrow$ Cotyledonary.

Answer 1

The Correct Option is A

Concept: Somatic embryogenesis follows a morphological path very similar to zygotic (seed) embryogenesis. The embryo passes through distinct shapes as it develops its bipolar structure.

Step 1: Callus Initiation.
The process begins with the Initiation of embryogenic callus (B). Under high auxin levels (typically 2,4-D), cells de-differentiate and form clusters of embryogenic cells (pro-embryogenic masses).

Step 2: Morphological Stages.
Once the embryogenic cells begin to divide, they follow a standard geometric progression:
• Globular Stage (C): A spherical mass of cells.
• Heart Stage: (Not listed here, but follows globular).
• Torpedo Stage (A): Elongated structure where the root and shoot poles are distinct.
• Cotyledonary Stage (D): The final stage where "green" seed-leaves develop, preparing the embryo for germination.