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Question
Explain the monosporic development of the embryo sac in the ovule of an angiosperm.
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Solution
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.
RELATED QUESTIONS
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
The method of embryo sac forming from a single megaspore is called ______.
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.
Draw a diagram of the mature embryo sac of an angiospermic ovule and label any four parts in it.
In the first mitotic division of the functional megaspore, the two daughter nuclei move to opposite poles of the enlarging megaspore. What stage is this called?
The mature embryo sac is described as monosporic and of the Polygonum type. What does the term monosporic indicate about the origin of the embryo sac?
During the development of the embryo sac, which stage immediately precedes the formation of the polar nuclei by migration?
In the mature embryo sac, which structure contains the filiform apparatus that aids in guiding the pollen tube?
