Name: Types of Cross-Pollination
Uploaded: 2019-07-19
Duration: 4 min 6 s
Description: It can't bee!? Bees and butterflies are common pollinators, but many other types of animals and abiotic factors aid pollination. Explore the world of pollina...

Question

With a neat diagram, explain the development of 7-celled, 8 nucleate female gametophyte in angiosperm.

Accepted Answer

In angiosperms, the embryo sac is the female gametophyte. The embryo sac is a haploid structure developed from a diploid megaspore mother cell by meiosis. During development, the megaspore mother cell undergoes meiosis and forms a linear tetrad of 4 haploid megaspores. Three haploid spores are degenerates at micropylar end and remain one functional megaspore at chalazal end.

Functional megaspore undergoes three free nuclear mitotic divisions. The first division produces two nucleate embryo sac. The two nuclei shift to the two ends and divide there twice forming four nucleate and then eight nucleate structure. One nucleus from each end moves to the middle. These are called polar nuclei.

The remaining three nuclei at the two ends form three celled egg apparatus at micropylar end and the three celled antipodals at the chalazal end. The middle binucleated part organises itself into a central cell.

Mature embryo sac has 7cells and 8 nuclei and is called Polygonum type. The two polar nuclei are fused to form the secondary nucleus.

With a neat diagram, explain the development of 7-celled, 8 nucleate female gametophyte in angiosperm.

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