Q.Describe the 7-celled, 8-nucleate organisation of a typical angiosperm embryo sac formed by the monosporic (Polygonum) pattern of development.

It forms by three free-nuclear mitotic divisions of the functional megaspore without accompanying cell-wall formation, followed by cellularisation. …

In the monosporic (Polygonum) pattern, the single functional megaspore's nucleus divides mitotically, without accompanying cytokinesis, in three successive rounds, producing 8 free nuclei within one large cell. These 8 nuclei then organise and cell walls form around most of them (except the two that remain together), producing a total of 7 cells housing 8 nuclei -- hence '7-celled, 8-nucleate'.

Of these, three nuclei/cells group together at the micropylar end as the egg apparatus: one egg cell flanked by two synergids (which possess a filiform apparatus that guides the entering pollen tube). Three more nuclei/cells group at the opposite, chalazal end as the antipodal cells, whose function is thought to be nutritive and is not fully essential. The two remaining nuclei, called polar nuclei, migrate …

Trace three free-nuclear divisions of the functional megaspore (2->4->8 nuclei), then place the 8 nuclei into their th …

Miscounting cells versus nuclei -- the central cell is ONE cell but has TWO nuclei (polar nuclei), which is e …