Step 1: Understanding the Concept:
The female gametophyte of angiosperms is referred to as the embryo sac.
It develops from a functional megaspore through the process of megagametogenesis.
In a typical angiosperm (like {Polygonum}), the mature embryo sac is a 7-celled, 8-nucleate structure.
This structure is highly polarized, meaning specific cell types are always found at specific ends of the sac, determined by the orientation of the ovule.
Step 2: Detailed Explanation:
The organization of the 7-celled embryo sac is as follows:
1. Micropylar End: This is the end where the micropyle (opening of the ovule) is situated. It contains the egg apparatus, which consists of three cells: two synergids and one egg cell. The synergids have special cellular thickenings called the filiform apparatus to guide the pollen tube.
2. Central Part: This contains a single, very large central cell. Initially, this cell contains two polar nuclei, which typically fuse just before fertilization to form a single diploid secondary nucleus.
3. Chalazal End: This is the end opposite to the micropyle. It contains three cells known as the antipodal cells.
Antipodal cells are generally considered vegetative cells of the female gametophyte. Their exact function can vary between species; in some, they degenerate before fertilization, while in others, they may persist and assist in providing nutrition to the developing embryo.
The question asks specifically for the location of these antipodals, which is the chalazal pole.
Step 3: Final Answer:
Based on the anatomical structure of the ovule, the antipodals are located at the chalazal end.
Option (B) is incorrect because the egg apparatus is at the micropylar end.
Option (C) is incorrect because the central cell is in the middle.
Option (D) is incorrect because a synergid is a specific cell type, not a region of the embryo sac.
Step 4: Final Answer:
The correct answer is (A).