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

(C) The pistil or gynoecium represents the female reproductive part of a flower. It consists of three distinct parts:
$1$. Stigma: The landing platform for pollen grains.
$2$. Style: The elongated slender part beneath the stigma.
$3$. Ovary: The swollen basal part containing the ovules.
Therefore,the correct answer is $3$.

(B) The pistil or carpel consists of three parts: the stigma, the style, and the ovary.
$1$. The $Stigma$ serves as a landing platform for pollen grains.
$2$. The $Style$ is the elongated slender part beneath the stigma.
$3$. The $Ovary$ is the basal bulged part of the pistil.
Therefore, the correct option is $B$.

(B) The ovarian cavity (locule) contains the placenta.
Inside the ovary,the placenta is the site where the ovules are attached.
Therefore,the placenta is present inside the ovarian cavity,which supports the development of ovules.

(B) In angiosperms,the ovule is the structure that develops into the seed after fertilization. Morphologically and functionally,the ovule is equivalent to the megasporangium. Inside the megasporangium,the megaspore mother cell undergoes meiosis to produce megaspores,which eventually develop into the female gametophyte (embryo sac).

(A) In flowering plants,the ovule is attached to the placenta,which is a flattened,cushion-like tissue located within the ovary. The placenta is connected to the ovary wall. Therefore,the ovule is attached to the placenta.

(C) The ovule is a structure in seed plants that develops into a seed after fertilization.
It is protected by one or more layers of tissue known as the integuments.
These integuments eventually harden to form the seed coat after fertilization.
Therefore,the protective covering of the ovule is called the integument.

(D) The megasporangium (ovule) is attached to the placenta by means of a stalk called the $Funiculus$.
$1$. The point of attachment of the body of the ovule with the $Funiculus$ is known as the $Hilum$.
$2$. The $Nucellus$ is the central mass of tissue within the ovule.
$3$. The $Embryo \text{ } sac$ is the female gametophyte located inside the $Nucellus$.
$4$. The $Chalaza$ represents the basal part of the ovule opposite to the micropyle.

(C) In an angiosperm ovule, the main body of the ovule is composed of a mass of parenchymatous tissue called the $Nucellus$.
This $Nucellus$ is protected by one or two protective envelopes known as $Integuments$.
The $Integuments$ surround the $Nucellus$ except at the tip where a small opening called the $Micropyle$ is present.

(B) The megasporangium (ovule) is surrounded by protective layers called integuments.
These integuments encircle the nucellus except at the tip,where a small opening is left.
This small opening is known as the $Micropyle$.
It serves as the entry point for the pollen tube during fertilization.

(D) In the structure of an angiosperm ovule,the micropyle is the small opening at one end. The pole directly opposite to the micropyle is known as the chalaza. The chalaza represents the basal part of the ovule.

(A) The ovule is a small structure attached to the placenta by means of a stalk called the funiculus. The body of the ovule fuses with the funiculus in the region called the hilum. Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is organized. The nucellus is a mass of cells enclosed within the integuments that contains reserve food materials.

(A) The $nucellus$ is the central part of the $megasporangium$ (ovule) in flowering plants. It consists of a mass of parenchymatous cells enclosed within the integuments. The $megasporangium$ is the structure that develops into the seed after fertilization. Therefore,the $nucellus$ is a characteristic feature of the $megasporangium$.

(A) In angiosperms,the ovule consists of a central mass of tissue called the nucellus,which is protected by integuments. Within the nucellus,a single megaspore mother cell differentiates and undergoes meiosis to form megaspores. One of these megaspores develops into the female gametophyte,which is known as the embryo sac. Therefore,the embryo sac develops inside the nucellus.

(C) The embryo sac is the female gametophyte in flowering plants.
It develops from the functional megaspore within the ovule (megasporangium).
It typically consists of $7$ cells and $8$ nuclei at maturity.
Therefore,the correct option is $C$.

(A) In most angiosperms,a single megaspore mother cell $(MMC)$ undergoes meiosis to produce four haploid megaspores. Out of these four,three degenerate and only one functional megaspore develops into the female gametophyte (embryo sac). This is known as monosporic development. Therefore,a single megasporangium typically contains only one female gametophyte.

(D) Megasporogenesis is the process of formation of megaspores from the megaspore mother cell $(MMC)$.
In this process,a diploid $MMC$ undergoes meiosis to produce four haploid megaspores.
Therefore,the correct sequence is $MMC \rightarrow \text{Megaspore}$.

(A) In the process of megasporogenesis,a single cell of the nucellus,usually towards the micropylar end,differentiates into a Megaspore Mother Cell $(MMC)$.
This cell is large and contains dense cytoplasm and a prominent nucleus.
Therefore,typically,there is only one $MMC$ present in the nucellus of an ovule.

(B) The megaspore mother cell $(MMC)$ is a diploid cell derived from the nucellus of the ovule.
It undergoes meiosis to produce four haploid megaspores.
Therefore,the ploidy of the megaspore mother cell is $2n$.

(B) The process of formation of megaspores from the megaspore mother cell $(MMC)$ is known as megasporogenesis.
In this process,the diploid $MMC$ undergoes meiosis (reduction division) to produce four haploid megaspores.
Therefore,the correct process is meiosis.

(D) During megasporogenesis,one megaspore mother cell $(MMC)$ undergoes meiosis to produce $4$ haploid megaspores.
Therefore,$100$ $MMC$s will produce $100 \times 4 = 400$ megaspores $(a = 400)$.
In a typical angiosperm,out of the $4$ megaspores,$3$ degenerate $(b)$ and only $1$ remains functional $(c)$.
For $100$ $MMC$s,the number of degenerating megaspores is $100 \times 3 = 300$ $(b = 300)$.
The number of functional megaspores is $100 \times 1 = 100$ $(c = 100)$.

(B) In the development of the female gametophyte (embryo sac) from a functional megaspore,the nucleus undergoes free nuclear divisions.
$1$. The nucleus of the functional megaspore divides by mitosis to form two nuclei,which move to opposite poles,forming the $2-$nucleate embryo sac.
$2$. This is followed by two more successive mitotic divisions,leading to $4-$nucleate and then $8-$nucleate stages.
$3$. Therefore,the movement of nuclei towards opposite poles occurs after the first mitotic division.

(B) The development of the embryo sac from a single functional megaspore is known as monosporic development.
$1$. The nucleus of the functional megaspore undergoes the first mitotic division to form two nuclei.
$2$. These two nuclei undergo a second mitotic division to form four nuclei.
$3$. These four nuclei undergo a third mitotic division to form eight nuclei.
Thus,a total of $3$ successive mitotic divisions are required to produce $8$ nuclei from a single functional megaspore.

(A) In angiosperms,the megaspore mother cell undergoes meiosis to produce four megaspores.
Three of these degenerate,and the remaining one develops into the embryo sac.
The embryo sac is a seven-celled,eight-nucleate structure that represents the female gametophyte in flowering plants.

(A) In the development of a typical angiosperm embryo sac (Polygonum type),the functional megaspore undergoes three successive free nuclear mitotic divisions.
$1$. The first division results in a $2$-nucleate stage.
$2$. The second division results in a $4$-nucleate stage.
$3$. The third division results in an $8$-nucleate stage.
After the $8$-nucleate stage,cell walls are laid down,leading to the organization of the typical $7$-celled and $8$-nucleate embryo sac.

(C) In a typical angiosperm embryo sac,there are $8$ nuclei in total.
Out of these $8$ nuclei,$6$ nuclei are surrounded by cell walls and organized into cells.
These include $3$ cells of the egg apparatus (one egg cell and two synergids) at the micropylar end and $3$ antipodal cells at the chalazal end.
The remaining $2$ nuclei,known as polar nuclei,are situated in the large central cell and are not surrounded by individual cell walls.
Therefore,the correct answer is $6$.

(B) The filiform apparatus is a specialized cellular thickening of the cell wall in the synergids.
It consists of finger-like projections that extend into the cytoplasm of the synergid cells.
The primary function of the filiform apparatus is to guide the entry of the pollen tube into the synergid.

(B) In the process of embryo sac development in angiosperms,the mature embryo sac typically consists of $7$ cells and $8$ nuclei.
Among these,the central cell is the largest cell.
It contains two polar nuclei,which eventually fuse to form a single diploid secondary nucleus before fertilization.
Therefore,the central cell contains two nuclei.

(C) In a typical angiosperm embryo sac,the egg apparatus is located at the micropylar end. The egg apparatus consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus,which guide the pollen tube into the synergid. Therefore,the egg cell is situated at the micropylar end.

(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. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus,which guide the pollen tube into the synergid. Therefore,the egg cell and the two synergids together constitute the egg apparatus.

(B) mature female gametophyte (embryo sac) in angiosperms typically consists of $7$ cells and $8$ nuclei.
These cells include $3$ antipodal cells,$1$ central cell (with $2$ polar nuclei),$1$ egg cell,and $2$ synergid cells.
The synergid cells are located at the micropylar end and play a crucial role in guiding the pollen tube towards the egg cell.
Therefore,there are $2$ synergid cells present in a mature female gametophyte.

(A) In a typical angiosperm embryo sac (polygonum type),the organization is as follows:
$1$. Antipodal cells: These are $3$ cells located at the chalazal end.
$2$. Central cell: There is $1$ large central cell containing $2$ polar nuclei.
$3$. Egg cell: There is $1$ egg cell located at the micropylar end.
$4$. Synergids: There are $2$ synergids located at the micropylar end along with the egg cell.
Therefore,the sequence is $3$ antipodal cells,$1$ central cell,$1$ egg cell,and $2$ synergids. The correct option is $A$.

(B) In a typical angiosperm embryo sac,the cells are organized as follows:
$1$. At the micropylar end,there is an egg apparatus consisting of one egg cell and two synergids.
$2$. At the chalazal end,there are three cells known as antipodal cells.
$3$. In the center,there is a large central cell with two polar nuclei.
Therefore,the cells located at the chalazal end are the antipodal cells.

(B) In angiosperms,the mature female gametophyte is known as the embryo sac.
According to the development of a typical monosporic embryo sac (Polygonum type),one functional megaspore develops into one embryo sac.
Therefore,$1$ mature female gametophyte contains $1$ embryo sac.
Consequently,$100$ mature female gametophytes will contain $100 \times 1 = 100$ embryo sacs.

(A) The egg cell (or oosphere) is the female gamete in flowering plants.
It is a haploid cell produced within the embryo sac.
The embryo sac itself represents the female gametophyte.
Therefore,the egg cell specifically represents the female gamete.

(B) 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.
Thus,the total number of cells is $3 + 2 + 1 + 1 = 7$ cells,and the total number of nuclei is $3 + 2 + 1 + 2 = 8$ nuclei.

(C) In flowering plants,the female gamete (egg cell) is formed within the embryo sac.
$1$. The embryo sac is also known as the female gametophyte.
$2$. It develops inside the ovule (megasporangium).
$3$. Within the embryo sac,the egg apparatus consists of two synergids and one egg cell (female gamete).
$4$. Pollen grains produce male gametes,while the anther is the part of the stamen that produces pollen.

(A) In wind-pollinated flowers,each ovary typically contains a single ovule (megasporangium). This is an adaptation to ensure efficient seed production,as wind pollination is a random process and having a single ovule per ovary is common in many wind-pollinated plants like grasses and cereals.

(A) In maize $(Zea \, mays)$, each ovary typically contains a single ovule. This is a characteristic feature of many monocotyledonous plants where the ovary develops into a single-seeded fruit (caryopsis). Therefore, the correct answer is $A$.

(D) $1$. The megaspore mother cell $(MMC)$ undergoes a single meiotic division to produce four haploid megaspores.
$2$. Out of these four,three degenerate,and one functional megaspore develops into the embryo sac.
$3$. The nucleus of the functional megaspore undergoes three successive free nuclear mitotic divisions to form $8$ nuclei.
$4$. These nuclei then organize into a $7$-celled,$8$-nucleate mature embryo sac.
$5$. Therefore,the process requires $1$ meiotic division and $3$ mitotic divisions.

(B) The structure of a mature embryo sac in angiosperms consists of:
$1$. Synergids: These are two specialized cells present at the micropylar end, which possess a special cellular thickening called the filiform apparatus that guides the pollen tube into the synergid.
$2$. Central cell: This is the largest cell of the embryo sac, containing two polar nuclei.
$3$. Antipodals: These are three cells situated at the chalazal end of the embryo sac.
$4$. Egg cell: This is the female gamete located at the micropylar end, flanked by the two synergids.
Matching these:
$(a)$ Synergids - $(3)$ Filiform apparatus
$(b)$ Central cell - $(4)$ Polar nuclei
$(c)$ Antipodals - $(2)$ Chalazal end
$(d)$ Egg cell - $(1)$ Female gamete
Therefore, the correct sequence is $a-3, b-4, c-2, d-1$.

(A) In the process of megasporogenesis,a single megaspore mother cell $(MMC)$ undergoes meiosis to produce four megaspores. Out of these,three degenerate and only one functional megaspore develops into the embryo sac. Therefore,statement $A$ is correct.
Statement $B$ is incorrect because only one embryo sac is typically formed from a single functional megaspore (monosporic development).
Statement $C$ is incorrect because a mature embryo sac is $7$-celled and $8$-nucleated.
Statement $D$ is incorrect because a mature embryo sac contains only one egg apparatus.

(C) The provided figure represents the structure of an anatropous ovule (megasporangium).
It shows various parts such as the funicle,hilum,integuments,micropyle,nucellus,and embryo sac.
Therefore,the correct identification of the given figure is an ovule.

(A) Based on the structure of a typical anatropous ovule:
- 'a' points to the Hilum,which is the junction between the ovule and the funicle.
- 'b' points to the Funicle,the stalk that attaches the ovule to the placenta.
- 'c' points to the Micropyle,the small opening at the apex of the ovule through which the pollen tube enters.
Therefore,the correct sequence is Hilum,Funicle,and Micropyle.

(D) In the provided diagram of an anatropous ovule:
- '$a$' represents the Funiculus.
- '$b$' represents the Hilum.
- '$c$' represents the Micropyle.
- '$d$' represents the Micropylar pole.
- '$e$' represents the Nucellus.
- '$f$' represents the Embryo sac.
- '$g$' represents the Chalaza.
Therefore,'$d$' is the Micropylar pole and '$e$' is the Nucellus.

(A) In the provided diagram of an anatropous ovule:
- '$a$' represents the Hilum.
- '$b$' represents the Funiculus.
- '$c$' represents the Micropyle.
- '$d$' represents the Outer integument.
- '$e$' represents the Nucellus.
- '$f$' represents the Embryo sac.
- '$g$' represents the Chalazal pole.
Therefore,'$f$' is the Embryo sac and '$g$' is the Chalazal pole.

(B) In the structure of a mature embryo sac (Polygonum type):
$1$. '$a$' points to the group of three cells located at the chalazal end,which are known as Antipodal cells.
$2$. '$b$' points to the two nuclei located in the center of the large central cell,known as Polar nuclei.
Therefore,'$a$' represents Antipodal cells and '$b$' represents Polar nuclei.

(C) In the provided diagram of a mature embryo sac (Polygonum type):
- '$a$' represents antipodal cells.
- '$b$' represents polar nuclei.
- '$c$' represents the egg cell.
- '$d$' represents synergids.
- '$e$' represents filiform apparatus.
The egg cell is a haploid $(n)$ gamete formed within the embryo sac. Therefore,'$C$' is the egg cell and its ploidy is $n$.

(B) In the given diagram of a mature embryo sac (polygonum type):
- '$a$' represents Antipodal cells.
- '$b$' represents Polar nuclei.
- '$c$' represents Central cell.
- '$d$' represents Synergids.
- '$e$' represents Filiform apparatus.
Therefore,'$d$' and '$e$' represent Synergids and Filiform apparatus respectively.

(B) In the provided diagram of a longitudinal section of a carpel showing pollen tube entry into the ovule:
- '$P$' represents the pollen tube.
- '$Q$' represents the antipodal cells.
- '$R$' represents the central cell (polar nuclei).
- '$S$' represents the egg cell.
- '$T$' represents the synergid cell.
Therefore,'$S$' and '$T$' represent the egg cell and synergid,respectively.

(D) In angiosperms,one $MMC$ (Megaspore Mother Cell) undergoes meiosis to produce four haploid megaspores.
Out of these four megaspores,usually only one remains functional,while the other three degenerate.
Therefore,$1$ $MMC$ produces $1$ functional megaspore.
To produce $800$ functional megaspores,we require $800$ $MMC$s.