The Pistil, Megasporangium (ovule) and Embryo sac Questions in English

(B) During the process of megasporogenesis,the megaspore mother cell undergoes meiosis to produce four haploid megaspores.
In the majority of flowering plants,three of these four megaspores degenerate,while only one megaspore remains functional.
This functional megaspore develops into the female gametophyte (embryo sac).
Therefore,the correct answer is $3$ megaspores degenerate and $1$ megaspore remains functional.

(A) typical mature embryo sac (Polygonum type) is formed after three rounds of free nuclear divisions following meiosis of the megaspore mother cell.
It contains $8$ nuclei: $3$ at the micropylar end (egg apparatus),$3$ at the chalazal end (antipodals),and $2$ polar nuclei in the central cell.
However,it is $7$-celled because the two polar nuclei fuse to form a single central cell,while the other $6$ nuclei are enclosed in individual cell membranes.
Thus,it is $8$-nucleate and $7$-celled.

(A) Monosporic development refers to the process where the embryo sac (female gametophyte) develops from only one of the four megaspores produced after meiosis of the megaspore mother cell. In most flowering plants,three megaspores degenerate,and only one functional megaspore undergoes mitosis to form the mature embryo sac (Polygonum type).

(C) In the mature embryo sac of angiosperms,the egg apparatus is located at the micropylar end.
It consists of two synergids and one egg cell.
Therefore,the egg apparatus is defined as the combination of the egg cell and the two synergids.

(B) The filiform apparatus is a specialized cellular thickening located at the micropylar end of the synergids.
Its primary function is to secrete chemical substances that guide the entry of the pollen tube into the synergids during the process of fertilization in angiosperms.

(A) In a typical mature angiosperm embryo sac,the arrangement of nuclei is as follows:
$1$. At the micropylar end,there are $3$ cells: $2$ synergids and $1$ egg cell.
$2$. In the central cell,there are $2$ polar nuclei.
$3$. At the chalazal end,there are $3$ antipodal cells.
Therefore,the arrangement of nuclei is $3$ (antipodals) $+ 2$ (polar nuclei) $+ 3$ (egg apparatus) = $3+2+3$.

(A) In a typical angiosperm embryo sac,there are $8$ nuclei and $7$ cells.
$1$. The three cells located at the chalazal end are known as antipodal cells $(P)$.
$2$. The three cells located at the micropylar end constitute the egg apparatus $(Q)$,which consists of one egg cell and two synergids.
$3$. Therefore,$P$ represents antipodal cells and $Q$ represents the egg apparatus.
Thus,the correct option is $A$.

(D) In a typical angiosperm embryo sac,the $7$-celled and $8$-nucleate structure consists of three antipodal cells,two synergids,one egg cell,and one large central cell.
The central cell is the largest cell of the embryo sac because it occupies the major portion of the embryo sac and contains two polar nuclei before fusion.
Therefore,the correct option is $D$.

(D) The filiform apparatus is a specialized cellular thickening present in the synergids of the embryo sac. It is located at the micropylar end of the synergids. Its primary function is to guide the entry of the pollen tube into the synergids during fertilization.

(A) In the provided diagram of the embryo sac,the labels represent the following structures:
$P$ represents the synergids.
$Q$ represents the egg cell.
$R$ represents the filiform apparatus.
$S$ represents the antipodal cells.
Synergids are specialized cells present at the micropylar end of the embryo sac that help in guiding the pollen tube towards the egg cell.
Therefore,the correct option is $A$.

(A) The typical mature embryo sac of angiosperms is $7$-celled and $8$-nucleate.
It consists of the following components:
$1$. An egg apparatus at the micropylar end,which includes one egg cell and two synergids.
$2$. Three antipodal cells at the chalazal end.
$3$. $A$ large central cell containing two polar nuclei,which eventually fuse to form a diploid secondary nucleus.
Therefore,the correct composition is one egg cell,two synergids,three antipodal cells,and two polar nuclei.

(C) Assertion $(A)$ is true. $A$ mature,typical angiosperm embryo sac (Polygonum type) undergoes three rounds of free nuclear mitotic divisions,resulting in $8$ nuclei. These are organized into $7$ cells: $3$ antipodal cells,$1$ central cell (containing $2$ polar nuclei),and the egg apparatus consisting of $2$ synergids and $1$ egg cell.
Reason $(R)$ is false. The egg apparatus consists of $1$ egg cell and $2$ synergids. The $2$ polar nuclei are located in the large central cell,not in the egg apparatus.

(C) $1$. The development of a mature female gametophyte (embryo sac) starts from a diploid megaspore mother cell $(MMC)$.
$2$. The $MMC$ undergoes one meiotic division to produce four haploid megaspores.
$3$. Out of these four megaspores,three degenerate and only one functional megaspore develops into the female gametophyte.
$4$. This functional megaspore undergoes three successive free nuclear mitotic divisions to form an $8$-nucleated embryo sac.
$5$. Therefore,the process requires $1$ meiotic division and $3$ mitotic divisions.

(A) The correct matches are as follows:
$(a)$ Funicle: It is the stalk that attaches the ovule to the placenta,so $(a-ii)$.
$(b)$ Integuments: These are the protective layers surrounding the nucellus of the ovule,so $(b-iii)$.
$(c)$ Chalaza: It represents the basal part of the ovule,opposite to the micropylar end,so $(c-v)$.
$(d)$ Hilum: It is the junction point where the body of the ovule fuses with the funicle,so $(d-iv)$.
$(e)$ Micropyle: It is a small opening at the tip of the ovule through which the pollen tube enters,so $(e-i)$.
Therefore,the correct combination is $(a-ii, b-iii, c-v, d-iv, e-i)$.

(B) In angiosperms,the female gametophyte is known as the embryo sac.
It is a small,seven-celled,and eight-nucleated structure that develops within the nucellus of the ovule.
The process begins with a single megaspore mother cell undergoing meiosis to produce four megaspores,of which three degenerate and one functional megaspore develops into the embryo sac.

(A) In the process of megasporogenesis,the megaspore mother cell undergoes meiosis to produce four megaspores.
In the majority of angiosperms,three megaspores degenerate,and only one remains functional.
This single functional megaspore develops into the embryo sac,which is known as monosporic development.
Therefore,both the assertion and the reason are true,and the reason correctly explains why it is called monosporic development.

(D) The filiform apparatus is a specialized cellular thickening of the cell wall in the synergid cells of the embryo sac.
It consists of finger-like projections that extend into the cytoplasm of the synergids.
Its primary function is to guide the entry of the pollen tube into the synergids during the process of fertilization.
Therefore,the filiform apparatus is a characteristic feature of the synergids.

(C) The correct matches are as follows:
$1$. Hilum $(A)$: It is the junction between the ovule and the funicle $(III)$.
$2$. Perisperm $(B)$: It refers to the residual persistent nucellus in some seeds $(I)$.
$3$. Chalaza $(C)$: It represents the basal part of the ovule,opposite to the micropyle $(II)$.
$4$. Funicle $(D)$: It is the stalk by which the ovule is attached to the placenta $(IV)$.
Therefore,the correct matching is $A-III, B-I, C-II, D-IV$.

(B) In a typical angiosperm embryo sac,the organization is $7$-celled and $8$-nucleate.
At the micropylar end,there is an egg apparatus consisting of one egg cell and two synergids.
At the chalazal end,there are three cells known as antipodal cells.
The central cell contains two polar nuclei.
Therefore,the three cells at the chalazal end are called antipodal cells.

(A) $1$. The process begins with a diploid megaspore mother cell $(MMC)$.
$2$. The $MMC$ undergoes one meiotic division (meiosis) to produce four haploid megaspores.
$3$. Three of these megaspores degenerate,and one functional megaspore develops into the female gametophyte (embryo sac).
$4$. The nucleus of the functional megaspore undergoes three successive free nuclear mitotic divisions to form an $8$-nucleated structure.
$5$. These nuclei then organize into the $7$-celled,$8$-nucleated mature embryo sac.
$6$. Therefore,the formation requires $1$ meiotic division and $3$ mitotic divisions.

(C) In angiosperms,the process of megasporogenesis results in the formation of four megaspores from a megaspore mother cell $(MMC)$ through meiosis.
Out of these four megaspores,three degenerate,and only one remains functional.
This single functional megaspore undergoes three successive rounds of free-nuclear mitotic divisions to form an $8$-nucleate structure,which eventually organizes into the embryo sac (also known as the female gametophyte).
Therefore,the functional megaspore develops into the embryo sac.

(A) In the development of a typical angiosperm female gametophyte (embryo sac),the nucleus of the functional megaspore undergoes three successive mitotic divisions to form $8$ nuclei.
After the $8$-nucleate stage,cell walls are laid down,leading to the organization of the typical female gametophyte.
Specifically,$3$ nuclei move to the micropylar end to form the egg apparatus,and $3$ nuclei move to the chalazal end to form antipodal cells.
The remaining $2$ nuclei,known as polar nuclei,migrate from each pole (one from the micropylar end and one from the chalazal end) to the centre of the embryo sac.
Therefore,$1$ nucleus from each pole migrates to the centre,making a total of $2$ polar nuclei in the central cell.

(C) The stalk that attaches the ovule to the placenta of the ovary is known as the funiculus.
$i$. Chalaza: The basal part of the ovule opposite to the micropyle.
$ii$. Hilum: The junction or point of attachment between the ovule body and the funiculus.
$iii$. Placenta: The tissue within the ovary wall to which the ovule is attached via the funiculus.

(A) $1$. The megaspore mother cell $(MMC)$ is a diploid cell $(2n)$ derived from the nucellus tissue.
$2$. The nucellus is the central part of the ovule consisting of diploid cells $(2n)$ that provide nutrition to the developing embryo sac.
$3$. The egg cell is a haploid gamete $(n)$ formed after meiosis and subsequent mitotic divisions within the embryo sac.
$4$. Therefore,the correct sequence of ploidy is $2n, 2n, n$.

(D) In a mature angiosperm embryo sac,there are $7$ cells and $8$ nuclei.
These include $3$ antipodal cells (haploid),$2$ synergids (haploid),$1$ egg cell (haploid),and $1$ central cell containing $2$ polar nuclei (haploid).
Thus,there are $7$ haploid nuclei ($3$ antipodals + $2$ synergids + $1$ egg + $1$ polar nucleus) and $1$ diploid nucleus (formed by the fusion of $2$ polar nuclei in the central cell).
Therefore,the embryo sac contains $7$ haploid and $1$ diploid nucleus.

(C) In flowering plants, the number of ovules in an ovary varies depending on the species.
- $Rice$, $Wheat$, and $Mango$ typically contain a single ovule in their ovary, which develops into a single seed.
- $Tomato$ (and other fruits like $Papaya$ and $Watermelon$) contains many ovules within its ovary, which develop into multiple seeds.
- Therefore, $Tomato$ is the correct answer as it exhibits more than one ovule.

(C) In the embryo sac of angiosperms,the egg nucleus,antipodal nuclei,and synergid nuclei are haploid $(n)$. The male gamete is also haploid $(n)$. However,the secondary nucleus (or definitive nucleus) is formed by the fusion of two polar nuclei,making it diploid $(2n)$. Therefore,the secondary nucleus is unlike the others regarding ploidy.

(C) In angiosperms,the mature embryo sac (female gametophyte) typically consists of $8$ nuclei and $7$ cells.
Since it contains multiple nuclei,it is described as multinucleate.
The $8$ nuclei are arranged as follows: $3$ at the micropylar end (egg apparatus),$3$ at the chalazal end (antipodals),and $2$ polar nuclei in the central cell.

(C) The typical angiosperm embryo sac is monosporic,meaning it develops from a single functional megaspore.
It is endosporic because it develops within the megaspore wall inside the ovule.
It consists of $7$ cells and $8$ nuclei at maturity (three antipodal cells,two synergids,one egg cell,and one central cell with two polar nuclei).

(D) In angiosperms,the megasporangium is also known as the ovule.
Most angiosperms have ovules that are surrounded by two protective layers called integuments.
An ovule with two integuments is termed as bitegmic.
While some plants may have unitegmic (one integument) or ategmic (no integument) ovules,the most common condition in angiosperms is bitegmic.

(A) During the development of the embryo sac (monosporic development),a diploid megaspore mother cell $(MMC)$ undergoes a single meiotic division to produce four haploid megaspores.
Out of these four,three degenerate,and one functional megaspore remains.
This functional megaspore then undergoes three successive rounds of free-nuclear mitotic divisions to form an $8$-nucleated embryo sac.

(C) In angiosperms,the ovule is technically referred to as the megasporangium. The main body of the ovule,which consists of a mass of diploid parenchymatous cells enclosed within the integuments,is called the nucellus. Since the megaspore mother cell differentiates within this tissue,the nucellus is considered the megasporangium proper.

(B) In angiosperms,the megaspore mother cell $(MMC)$ undergoes meiosis to produce four haploid megaspores.
These four megaspores are typically arranged in a linear row,which is known as a linear tetrad.
Out of these four,usually three degenerate,and only one functional megaspore develops into the embryo sac.

(C) In angiosperms,the process of megasporogenesis involves the formation of megaspores from the megaspore mother cell $(MMC)$ through meiosis.
Out of the four megaspores produced,three degenerate,and only one remains functional.
This functional megaspore is the first cell of the female gametophyte (embryo sac).
It undergoes mitotic divisions to develop into the mature embryo sac.

(D) In the mature embryo sac of angiosperms,the egg apparatus consists of two synergids and one egg cell.
The synergids possess special cellular thickenings at the micropylar end called the filiform apparatus.
The primary function of the filiform apparatus is to guide the entry of the pollen tube into the synergids.

(C) In flowering plants,the development of the female gametophyte (embryo sac) begins from a single functional megaspore.
$1$. The megaspore mother cell undergoes $1$ meiosis to produce $4$ haploid megaspores.
$2$. Out of these,$3$ degenerate and $1$ remains functional.
$3$. The functional megaspore undergoes $3$ successive rounds of free-nuclear mitosis to form an $8$-nucleate structure.
$4$. These nuclei then organize into the $7$-celled,$8$-nucleate embryo sac (female gametophyte).
Therefore,the process involves $1$ meiosis and $3$ mitosis.

(C) The ovule is attached to the placenta by a stalk called the $Funicle$. The point of attachment of the body of the ovule with the $Funicle$ is known as the $Hilum$. Therefore,the $Funicle$ acts as the stalk connecting the ovule to the placenta.

(B) In the provided diagram of the embryo sac, the structure labeled '$Y$' represents the finger-like projections at the micropylar end of the synergids, known as the filiform apparatus. The structure labeled '$X$' points to one of the two synergid cells located adjacent to the egg cell. Therefore, the correct identification is $X = \text{Synergid}$ and $Y = \text{Filiform apparatus}$. However, based on the standard labeling in $NCERT$ diagrams for this specific image, '$X$' points to the synergid and '$Y$' points to the filiform apparatus. Looking at the options provided, option $(B)$ matches this description.

(C) The Nucellus is a mass of diploid $(2n)$ cells within the ovule.
The Megaspore Mother Cell $(MMC)$ is derived from the nucellus and is also diploid $(2n)$.
The functional Megaspore is formed after meiosis of the $MMC$ and is haploid $(n)$.
The female gametophyte (embryo sac) develops from the functional megaspore through mitosis and is also haploid $(n)$.
Therefore,the correct sequence of ploidy is $2n, 2n, n, n$.

(B) The $Hilum$ is the junction or the point of attachment where the body of the ovule is fused with the funicle. The funicle is the stalk that attaches the ovule to the placenta of the ovary. Therefore,the correct option is $B$.

(C) In the provided diagram of an anatropous ovule:
$X$ points to the small opening at the apex of the ovule,which is the Micropyle.
$Y$ points to the mass of nutritive tissue enclosed within the integuments,which is the Nucellus.
Therefore,the correct identification is $X$ - Micropyle and $Y$ - Nucellus.

(B) In the process of megasporogenesis,the nucellus contains diploid $(2n)$ cells.
'$X$' represents the cells of the nucellus,which are diploid $(2n)$.
'$Y$' represents the megaspore mother cell $(MMC)$ or the developing megaspore,which undergoes meiosis to form haploid $(n)$ megaspores.
Therefore,the ploidy of '$X$' is $2n$ and the ploidy of '$Y$' is $n$.

(A) In the provided diagram of an anatropous ovule:
$X$ points to the central structure within the nucellus,which is the embryo sac (female gametophyte).
$Y$ points to the stalk that attaches the ovule to the placenta,known as the funicle.
Therefore,the correct identification is $X = \text{Embryo sac}$ and $Y = \text{Funicle}$.

(B) In a typical angiosperm,the embryo sac (female gametophyte) undergoes three successive mitotic divisions after the formation of the functional megaspore.
These divisions result in $8$ nuclei.
After the divisions,cell walls are laid down,leading to the organization of the typical female gametophyte.
It consists of $3$ antipodal cells,$2$ synergids,$1$ egg cell,and $1$ large central cell containing $2$ polar nuclei.
Thus,it is $8$-nucleate but $7$-celled because the two polar nuclei are enclosed within a single central cell.

(D) The correct answer is $D$.
In a typical angiosperm,the mature embryo sac (female gametophyte) is $8$-nucleated and $7$-celled.
It consists of $3$ antipodal cells,$2$ synergids,$1$ egg cell,and $1$ large central cell containing $2$ polar nuclei.

(B) megasporangium.
In angiosperms,the ovule is a specialized structure that develops into a seed after fertilization. Technically,the ovule is referred to as a megasporangium because it contains the nucellus (the megasporangium proper) surrounded by integuments.

(A) In the process of megasporogenesis,the megaspore mother cell $(MMC)$ undergoes meiosis to form four haploid megaspores.
Out of these four megaspores,three megaspores present towards the micropylar end degenerate,while only one megaspore present towards the chalazal end remains functional.
This functional megaspore develops into the female gametophyte (embryo sac).
The mature female gametophyte is typically $7$-celled and $8$-nucleated.

(B) The nucellus is a diploid $(2n)$ tissue in the ovule,but in a tetraploid plant,the somatic cells are $4n$.
Given that the tetraploid plant has $4n = 48$ chromosomes in its nucellus,the haploid number $(n)$ is $48 / 4 = 12$.
The egg cell and synergids are part of the embryo sac (gametophyte) and are haploid $(n)$.
Therefore,the number of chromosomes in the egg cell is $n = 12$ and in a synergid is $n = 12$.
Wait,re-evaluating the ploidy: If the plant is tetraploid $(4n)$,the gametes produced by meiosis are diploid $(2n)$.
Thus,$4n = 48$,so $2n = 24$.
Both the egg cell and synergids are haploid relative to the sporophyte,but since the sporophyte is $4n$,the gametophyte cells are $2n$.
Therefore,both the egg cell and the synergid contain $24$ chromosomes.

(B) The correct answer is $B$.
Antipodal cells are formed after the mitotic division of the functional megaspore within the embryo sac.
Since the megaspore is haploid $(n)$,the antipodal cells formed from it are also haploid $(n)$,not diploid $(2n)$.
Therefore,the pair 'Antipodals - $2n$' is incorrect.

(B) The correct answer is $B$.
An angiosperm embryo sac,also known as the female gametophyte,typically follows the $Polygonum$ type of development.
It consists of $7$ cells: $1$ egg cell,$2$ synergids,$3$ antipodal cells,and $1$ large central cell.
Although there are $7$ cells,there are $8$ nuclei because the central cell contains $2$ polar nuclei,while the other $6$ cells each contain $1$ nucleus.