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प्रश्न
Explain the monosporic development of the embryo sac in the ovule of an angiosperm.
उत्तर
Development of embryo sac:
The first cell of the female gametophyte is represented by the functional megaspore that grows along the micropylar known as the chalazal axis and is primarily chalazal. The functioning megaspore's nucleus divides during phase to produce two cells that migrate to the opposing poles to form the 2-nucleate embryo sac. The 4-nucleate and eventually the 8-nucleate stages of the embryo sac are created by two more consecutive mitotic nuclear divisions. One nucleus from each group at a pole migrates to the cell's core, becoming known as a polar nucleus. The three remaining cells form antipodals and are encircled by a wall towards the end of the chalazal. The egg apparatus is made up of three cells at the micropylar end, one of which is an egg or female gamete and the other two are synergids. The adult female gametophyte or embryo sac is the entire structure with two polar cells, three antipodals, one egg, and two synergids.
संबंधित प्रश्न
From among the sets of terms given below, identify those that are associated with the gynoecium.
From the statements given below choose the option that are true for a typical female gametophyte of a flowering plant.
- It is 8-nucleate and 7-celled at maturity
- It is free-nuclear during the development
- It is situated inside the integument but outside the nucellus
- It has an egg apparatus situated at the chalazal end
In an embryo sac, the cells that degenerate after fertilisation are ______.
In a flower, if the megaspore mother cell forms megaspores without undergoing meiosis and if one of the megaspores develops into an embryo sac, its nuclei would be ______.
Name the component cells of the ‘egg apparatus’ in an embryo sac.
Draw the diagram of a mature embryo sac and show its 8-nucleate, 7-celled nature. Show the following parts: antipodals, synergids, egg, central cell, polar nuclei.
With a neat, labelled diagram, describe the parts of a mature angiosperm embryo sac. Mention the role of synergids.
Embryo sacs of some apomictic species appear normal but contain diploid cells. Suggest a suitable explanation for the condition.
Trace the development of a megaspore mother cell to the formation of a mature embryo sac in a flowering plant.
Draw a diagram of the mature embryo sac of an angiospermic ovule and label any four parts in it.
