Name: Post Fertilization Events
Uploaded: 2019-07-19
Duration: 1 min 34 s
Description: This video discusses one of the essential concepts of the Human Reproductive System: Post-fertilization events. It stresses that post the fusion of the male and female gamete, the zygote formed undergoes mitotic division and develops into a blastocyst followed by an embryo and foetus.

Question

Draw a labelled diagram of the L.S. of anatropous ovule and list the components of embryo sac and mention their fate after fertilization.

Accepted Answer

The body of antropous ovule is rotated by 180° and micropylar comes near to the funiculus. Chalaza and micropyle lie in the straight line, but hilum is at 90° to micropyle. The body of ovule is fused to funiculus on one side, thus forming a ridge called Raphe.

In angiosperms, the female gametophyte is called the embryo sac. It is a multicellular haploid structure that is embedded in the nucellus of the ovule. A typical angiosperm embryo sac is 8 nucleated and 7 celled structure. It contains 3 antipodals, 3 synergids, 1 egg, and 2 polar nuclei.

After positive pollen–pistil interaction, the pollen tube develops and enters the ovule through synergids guided by the filiform apparatus. One of the male gametes fertilizes the egg to form a diploid zygote. Another male gamete fuses with the secondary nucleus (the product of fusion of polar nuclei) to form a triploid primary endosperm nucleus (PEN). After fertilization, the primary endosperm cell divides mitotically and forms a triploid endosperm tissue. The zygote divides repeatedly to form an embryo. Antipodals and synergids are disintegrated after fertilization.

Draw a labelled diagram of the L.S. of anatropous ovule and list the components of embryo sac and mention their fate after fertilization.

Important Questions on Reproduction in Lower and Higher Plants

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