Question

Egg cell formation in angiosperms involves me- gasporogenesis and female gametophyte development.

a) Briey write the various steps involved in female gametophyte development.

b) Mature angiosperm embryosac at maturity, though 8 nucleated is 7 celled.

What is your explanation related to this statement? Explain.

Answer 1

(a) Single megaspore mother cell (MMC) in the micropylar region of the nucellus undergoes meiotic division results in the production of four megaspores. In a majority of flowering plants, one of the megaspores is functional while the other three degenerate. Only one functional megaspore develops into the female gametophyte (embryo sac).

(b) 2 polar nuclei are situated below the egg apparatus in the large central cell. Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals.