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प्रश्न
With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
उत्तर
The female gametophyte (embryo sac) develops from a single functional megaspore. This megaspore undergoes three successive mitotic divisions to form eight nucleate embryo sacs.
The first mitotic division in the megaspore forms two nuclei. One nucleus moves towards the micropylar end while the other nucleus moves towards the chalazal end. Then, these nuclei divide at their respective ends and re-divide to form eight nucleate stages. As a result, there are four nuclei each at both the ends i.e., at the micropylar and the chalazal end in the embryo sac. At the micropylar end, out of the four nuclei, only three differentiate into two synergids and one egg cell. Together, they are known as the egg apparatus. Similarly, at the chalazal end, three out of four nuclei differentiate as antipodal cells. The remaining two cells (of the micropylar and the chalazal end) move towards the centre and are known as the polar nuclei, which are situated in a large central cell. Hence, at maturity, the female gametophyte appears as a 7-celled structure, though it has 8 nucleate.
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संबंधित प्रश्न
Answer the following question.
Where does the process of megasporogenis start in an angiosperm? Describe the process up to the formation of an embryo sac.
Answer the following question.
Draw the diagram of a pistil where pollination has successfully occurred. Label the parts involved in reaching the male gametes to its desired destination.
In the T.S. of a mature anther given below, identify "a" and "b" and mention their functions.
Egg apparatus consists of ______.
Ovules are attached to a parenchymatous cushion called ______.
Polygonum type of embryo sac/typical female gametophyte of angiosperms is ______.
Embryo sac is also known as ______.
Route used by pollen tube for entering ovule is ______.
Development of an organism from female gamete/egg without involving fertilization is ______.
Nucellus embryo is ______.
What is the direction of micropyle in anatropous ovule?
Which one of the following represents an ovule, where the embryo sac becomes horseshoe shaped and the funiculus and micropyle are close to each other?
Polygonum type of embryo sac is ______.
Megasporangium along with its protective integuments is called ______.
Which of the following occupies a central position in flower?
In the figure of anatropous ovule given below, choose the correct option for the characteristic distribution of cells within the typical embryo sac
| Number of cells at the chalazal end | Number of cells at micropylar end | Number of nuclei left in the central cell | |
| A | 3 | 2 | 3 |
| B | 3 | 3 | 2 |
| C | 2 | 3 | 3 |
| D | 2 | 2 | 4 |
Marginal placentation is present in ______.
Filiform apparatus is a characteristic feature of ______.
In a female gametophyte, the egg apparatus consists of ______
