Discussion
Which of the following statements about embryo sac development in plants is NOT CORRECT ?
Answer: D
The statement that is not correct is Polygonum type of embryo sac is derived from the micropylar megaspore of the tetrad and is eight nucleate.
In the Polygonum (monosporic) type, which occurs in most flowering plants, the three megaspores towards the micropyle degenerate and the chalazal megaspore develops. Three mitotic divisions give eight nuclei, which organise into seven cells. So 'eight nucleate' is right, but the functional megaspore is the chalazal one, not the micropylar one.
The other statements are correct. A mature embryo sac is usually seven-celled and eight-nucleate (three antipodals, two synergids, the egg and the binucleate central cell). The Plumbago type is tetrasporic: all four megaspore nuclei take part. The two synergids sit beside the egg at the micropylar end and are elongated cells with a filiform apparatus.
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