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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.
Draw the diagram of a pistil where pollination has successfully occurred. Label the parts involved in reaching the male gametes to its desired destination.
Among the terms listed below, those that of are not technically correct names for a floral whorl are:
- Androecium
- Carpel
- Corolla
- Sepal
The point at which funiculus touches the ovule 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 ______.
Female gametophyte of angiosperms is represented by ______.
Ovule is straight with funiculus, embryo sac, chalaza, and micropyle lying on one straight line. It is ______.
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?
Through which cell of the embryo sac, does the pollen tube enter the embryo sac?
During the process of fertilisation the pollen tube of the pollen grain usually enters the embryo sac through ______.
The Gynoecium of flower having two or more carpel fuse together are called ______.
Mark the odd one.
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 highly thickened structure commonly present in ______.
The hilum is a scar on the:
Megasporangium is equivalent to ______.
