Question

A mature embryo sac in a flowing plant ay possess 7-cells, but 8 nuclei. Explain with the help of diagram only.

Answer 1

In an embryo-sac three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus is consist of two synergids and one egg cell. The synergids have cellular thickenings at the micropylar tip called filiform apparatus, which plays an important role in guiding the pollen tubes into the synergids. Three cells are at the chalazal end and are called antipodals also the central cell contains 2 polar nuclei which are the result of karyokinesis not followed by immediate cell wall formation. Thus, a typical angiosperm embryo-sac at maturity, though 8-nucleate is 7-celled.