Question

Filiform apparatus is found in:

• A. Antipodal cell
• B. Egg cell
• C. Secondary nucleus
• D. Synergids

Hint:

Remember the 7-celled, 8-nucleate structure of the Polygonum-type embryo sac.
The "Egg Apparatus" at the micropylar end consists of 3 cells (1 Egg cell + 2 Synergids).
Only the synergids contain the filiform apparatus, which is essential for guiding the pollen tube.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
This question is from Plant Embryology, specifically the chapter "Sexual Reproduction in Flowering Plants" in the NCERT Class 12 curriculum.
We need to identify the cell within the female gametophyte (embryo sac) that contains the structure known as the filiform apparatus.

Step 2: Key Concept or Approach:
A mature female gametophyte (embryo sac) of angiosperms typically has a 7-celled and 8-nucleate structure.
At the micropylar end of the embryo sac, the egg apparatus consists of one central egg cell and two flanking synergids. The synergids feature prominent cellular thickenings at their micropylar tip, which are collectively called the filiform apparatus.

Step 3: Detailed Explanation:

• Synergids are highly specialized cells that lie on either side of the egg cell.

• The filiform apparatus consists of numerous finger-like projections of the inner cell wall of the synergid, which extend into its cytoplasm.

• This structure plays a crucial role in fertilization by performing the following functions:
- It guides the entry of the pollen tube into the synergid.
- It secretes chemical attractants (chemotropic substances) that direct the pollen tube's path through the micropyle.
- It helps in absorbing and transporting nutrients from the surrounding nucellus into the embryo sac.

• Let us analyze why the other options are incorrect:
- Antipodal cells are three cells located at the chalazal end of the embryo sac and lack any such specialized thickenings.
- The egg cell is the female gamete located between the synergids, which fuses with a male gamete to form a diploid zygote.
- The secondary nucleus (or definitive nucleus) is formed by the fusion of the two polar nuclei in the large central cell before fertilization.



Step 4: Final Answer:
The filiform apparatus is a characteristic feature found in the synergids, which corresponds to option (D).