(a)
(b) Components of embryo sac: 2 polar nuclei, 1 egg cell, 2 synergids and 3 antipodal cells.
After positive pollen−pistil interaction, the pollen tube develops and enters the ovule through synergids guided by filiform apparatus.
One of the male gamete fertilises the female gamete to form diploid zygote.
The other male gamete fuses with the secondary nucleus (polar nuclei if they are already fused) to form a triploid primary endosperm nucleus (PEN) that develops into endosperm.
The three antipodals at chalazal end and synergids at micropylar end start degenerating.
