Question

The egg apparatus consists of an
(a) Egg
(b) Egg and pollen nuclei
(c) Egg and synergids
(d) Egg and autopodals

Answer 1

Hint Egg apparatus develop from female gametophyte inside the embryo sac. The female gametophyte is a functional megaspore that undergoes free nuclear mitotic division to form an embryo sac consisting of seven cells and eight nuclei.

Complete Answer:
Egg apparatus is a group of three micropylar cells of embryo sac which are arranged in the form like an oosphere at middle and synergids at the lateral position. Synergids consist of terminal filiform apparatus. Synergids help in the absorption of nourishment from nucellus, it secretes a chemically active substance to attract pollen tube, it acts as a shock absorber for pollen tube and forms a seat for pollen tube discharge. Egg of egg apparatus represents the female gamete with the thick wall toward the micropylar end and the thin wall toward the chalazal end.

Additional information:
The embryo sac is a multicellular structure with one cell at the center, three at the micropylar end, and three at the chalazal end. Micropylar cells form egg apparatus whereas chalazal cells form antipodals cells and all these cells are connected with the help of plasmodesmata.
Antipodals cells possess several enzymes, starch, lipids, and proteins. These cells are vegetative cells that take part in the absorption of nourishment by developing historic and then they degenerate. A central cell of the embryo sac is the largest cell with two polar nuclei, vacuolated cytoplasm, and reserve food. Polar nuclei form a definitive nucleus. The central cell is the only cell that is diploid and it gives rise to the primary endosperm cell.

So, the correct answer is ‘Egg and synergids’.

Note: In microsporogenesis, all four microspores are functional whereas in megasporogenesis only one megaspore is functional and remains three degenerate. The haploid megaspore is formed by the diploid megaspore mother cell by mitotic or meiotic division by which the embryo sac may be monosporic, bisporic, and tetrasporic.