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

(C) Megasporogenesis is the process of formation of megaspores from the megaspore mother cell $(MMC)$.
In this process,the $MMC$ undergoes meiosis to produce four haploid megaspores.
Usually,only one megaspore remains functional while the other three degenerate.
Therefore,the statement that 'ovules differentiate into more than two megaspores' is incorrect because,although four are produced initially,they do not all remain as functional megaspores,and the process specifically results in a single functional megaspore in most angiosperms.

(B) In the process of megasporogenesis,a single cell in the micropylar region of the nucellus differentiates into the Megaspore Mother Cell $(MMC)$.
This $MMC$ undergoes meiosis to form four megaspores,out of which one becomes functional and develops into the embryo sac (female gametophyte).
Therefore,the correct answer is $MMC$.

(B) Statement $(I)$ is incorrect because the nucleus of the functional megaspore divides mitotically,not meiotically,to form two nuclei.
Statement $(II)$ is correct. After the $8$-nucleate stage,cell walls are laid down,leading to the organization of the typical female gametophyte (embryo sac).
Statement $(III)$ is correct. The egg apparatus is located at the micropylar end and consists of two synergids and one egg cell.
Statement $(IV)$ is correct. Three cells located at the chalaza end are known as antipodal cells.
Therefore,statements $(II), (III)$,and $(IV)$ are correct.

(C) Statement $(i)$ is correct: The gynoecium is the female reproductive part of the flower.
Statement $(ii)$ is incorrect: The ovule is located within the ovary,not the anther.
Statement $(iii)$ is correct: Each pistil (or carpel) consists of three parts: the stigma (landing platform for pollen),the style (elongated slender part),and the ovary (basal swollen part).
Statement $(iv)$ is incorrect: The uppermost part of the gynoecium is the stigma,while the anther is the terminal part of the stamen (male reproductive organ).

(A) The pistil (or carpel) is the female reproductive organ of a flower. It consists of three main parts:
$1$. The $Stigma$, which serves as a landing platform for pollen grains.
$2$. The $Style$, which is the elongated slender part beneath the stigma.
$3$. The $Ovary$, which is the basal bulged part containing the ovules.
A $Pollen \text{ tube}$ is a structure that grows from a pollen grain after pollination to deliver male gametes to the ovule; it is not a structural part of the pistil itself.

(D) In a typical angiosperm embryo sac,there are $3$ cells at the chalazal end,which are called antipodals,not $4$. Therefore,statement $A$ is incorrect.
$A$ typical mature angiosperm embryo sac consists of $8$ nuclei but only $7$ cells. These include $3$ antipodal cells at the chalazal end,$2$ synergids and $1$ egg cell at the micropylar end (forming the egg apparatus),and $1$ large central cell containing $2$ polar nuclei. Therefore,statement $R$ is correct.

(D) In a typical anatropous ovule,the stalk by which it is attached to the placenta is called the $X$ - Funicle.
The small opening at the apex of the ovule through which the pollen tube enters is the $Y$ - Micropyle.
The central mass of tissue enclosed within the integuments,which provides nutrition to the developing embryo,is the $Z$ - Nucellus.
Therefore,the correct labeling is $X$ - Funicle,$Y$ - Micropyle,and $Z$ - Nucellus.

(D) The process of formation of megaspores from the megaspore mother cell $(MMC)$ is known as megasporogenesis.
In this process,the diploid $MMC$ undergoes a single meiotic division (meiosis),which results in the production of four haploid megaspores.
These four megaspores are typically arranged in a linear tetrad.
Therefore,the correct answer is $4$.

(D) The mature embryo sac of a typical angiosperm (including dicotyledons) is $7$-celled and $8$-nucleate.
It consists of an egg apparatus (one egg cell and two synergids),three antipodal cells,and a central cell with two polar nuclei.
Antheridia are male sex organs found in bryophytes,pteridophytes,and some algae,but they are not present in the embryo sac of angiosperms.
Therefore,the correct option is $D$.

(C) The Gynoecium is the female reproductive part of a flower,consisting of one or more carpels (or pistils).
Each carpel typically consists of three parts: the $Stigma$,the $Style$,and the $Ovary$.
$Anther$ is a part of the $Stamen$ (the male reproductive organ or $Androecium$),not the $Gynoecium$.
Therefore,$Anther$ is the correct answer.

(C) In angiosperms, the female gametophyte is represented by the $Embryo \text{ } sac$.
$1$. The $Megaspore \text{ } mother \text{ } cell$ undergoes meiosis to produce four megaspores.
$2$. Out of these, three degenerate and one functional megaspore develops into the $Embryo \text{ } sac$ through mitosis.
$3$. The $Embryo \text{ } sac$ typically consists of $8$ nuclei and $7$ cells, representing the mature female gametophyte.

(C) The embryo sac,also known as the female gametophyte,develops within the nucellus of the ovule.
During the process of megasporogenesis,a single megaspore mother cell undergoes meiosis to produce four megaspores.
Usually,three of these degenerate,and the remaining functional megaspore develops into the embryo sac through the process of megagametogenesis.
Therefore,the embryo sac is formed inside the ovule.

(A) In an $Orthotropous$ (or $Atropous$) ovule,the body of the ovule is straight,and the funicle,hilum,micropyle,and chalaza lie in a single straight vertical line. This is considered the most primitive type of ovule and is found in plants like $Polygonum$ and $Piper$.

(B) An anatropous ovule is the most common type of ovule in angiosperms. In this type,the body of the ovule becomes completely inverted during development,such that the micropyle comes to lie very close to the funicle (stalk). Due to this inversion,the micropyle is directed downwards towards the placenta.

(A) In a $Hemitropous$ ovule,the body of the ovule is placed transversely at a right angle $(90^{\circ})$ to the funicle.
In this type,the nucellus and the embryo sac lie at a right angle to the funicle.
$Orthotropous$ ovules are straight,$Anatropous$ ovules are inverted $(180^{\circ})$,and $Campylotropous$ ovules have a curved body where the nucellus is bent.

(D) In an $Amphitropous$ ovule,the curvature of the ovule is so pronounced that the embryo sac becomes horseshoe-shaped. Due to this curvature,the funicle and the micropyle come very close to each other. This is a characteristic feature of $Amphitropous$ ovules.

(A) typical mature embryo sac of an angiosperm is $7$-celled and $8$-nucleate.
$1$. At the micropylar end,there is an egg apparatus consisting of $2$ synergids and $1$ egg cell ($3$ nuclei).
$2$. In the central cell,there are $2$ polar nuclei ($2$ nuclei).
$3$. At the chalazal end,there are $3$ antipodal cells ($3$ nuclei).
Therefore,the arrangement of nuclei is $3 + 2 + 3$.

(B) In angiosperms,the haploid $(n)$ structures are those formed after meiosis or those that are part of the gametophyte generation.
$1$. The egg cell is a haploid gamete formed within the embryo sac.
$2$. Antipodal cells are haploid cells located at the chalazal end of the embryo sac.
$3$. The megaspore mother cell $(2n)$ is diploid.
$4$. The nucellus $(2n)$ is diploid tissue.
$5$. The secondary nucleus $(2n)$ is diploid because it is formed by the fusion of two polar nuclei.
Therefore,both the egg cell and antipodal cells are haploid $(n)$.

(D) In angiosperms,the megasporangium is technically referred to as the ovule.
Inside the ovule,the nucellus is protected by integuments.
Within the nucellus,a single megaspore mother cell undergoes meiosis to produce megaspores,which eventually develop into the embryo sac.
Therefore,the entire structure of the ovule represents the megasporangium.

(D) The filiform apparatus consists of finger-like projections of the cell wall that extend into the cytoplasm of the synergids.
These structures are located at the micropylar end of the synergids.
Their 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.

(A) In angiosperms,the ovule is a specialized structure that develops into a seed after fertilization.
Structurally and functionally,the ovule is equivalent to the $Megasporangium$.
It contains the nucellus (the main body of the ovule) protected by integuments,where the megaspore mother cell undergoes meiosis to produce megaspores.

(C) In a majority of angiosperms,the megaspore mother cell $(MMC)$ undergoes meiosis (reduction division) to form four megaspores.
This is a characteristic feature of the development of the female gametophyte (embryo sac).
Option $A$ is incorrect because the filiform apparatus is present in synergids,not the egg cell.
Option $B$ is incorrect because there are typically only $3$ antipodal cells.
Option $D$ is incorrect because the central cell is the largest cell in the embryo sac.

(C) In angiosperms,the megaspore mother cell undergoes meiosis to produce four haploid megaspores.
Out of these four,three degenerate,and only one remains functional.
This functional megaspore undergoes three successive mitotic divisions to form an $8$-nucleated and $7$-celled structure known as the embryo sac (female gametophyte).

(D) In a hemianatropous ovule,the body of the ovule is rotated by $90^o$ with respect to the funicle.
As a result,the body of the ovule lies at a right angle $(90^o)$ to the funicle,not parallel to it.
Therefore,the Assertion is incorrect because the funicle is perpendicular to the body of the ovule,while the Reason is correct as it accurately describes the rotation of the ovule body.

(D) The Assertion is incorrect because the megaspore mother cell $(MMC)$ undergoes meiosis,not mitosis,to produce four megaspores.
The Reason is correct because the $MMC$ is diploid $(2n)$ and the resulting megaspores are haploid $(n)$.
Therefore,the Assertion is false,but the Reason is true.

(B) The most common type of embryo sac in angiosperms is the $Polygonum$ type,which is monosporic.
In this process,the functional megaspore undergoes three successive free nuclear mitotic divisions.
$1$. The first mitotic division results in $2$ nuclei.
$2$. The second mitotic division results in $4$ nuclei.
$3$. The third mitotic division results in $8$ nuclei.
These nuclei then organize into the $7$-celled,$8$-nucleate structure known as the mature embryo sac.

(N/A) An ovule is a female megasporangium where the formation of megaspores takes place.
The various parts of an ovule are:
$1$. Funiculus: It is a stalk-like structure which represents the point of attachment of the ovule to the placenta of the ovary.
$2$. Hilum: It is the point where the body of the ovule is attached to the funiculus.
$3$. Integuments: These are the protective envelopes surrounding the ovule. They provide protection to the developing embryo.
$4$. Micropyle: It is a small opening or pore at the tip of the ovule formed by the projection of integuments. It marks the point where the pollen tube enters the ovule at the time of fertilization.
$5$. Nucellus: It is a mass of parenchymatous tissue enclosed within the integuments. The nucellus provides nutrition to the developing embryo sac.
$6$. Chalaza: It is the basal part of the ovule,representing the point of origin of the integuments.

(N/A) The female gametophyte or the embryo sac develops from a single functional megaspore. This is known as monosporic development of the female gametophyte. In most flowering plants,a single megaspore mother cell $(MMC)$ present at the micropylar pole of the nucellus region of the ovule undergoes meiosis to produce four haploid megaspores. Later,out of these four megaspores,only one functional megaspore develops into the female gametophyte,while the remaining three degenerate.

(N/A) The female gametophyte (embryo sac) develops from a single functional megaspore. This megaspore undergoes three successive mitotic divisions to form an $8$-nucleate embryo sac.
The first mitotic division in the megaspore forms two nuclei. One nucleus moves towards the micropylar end while the other moves towards the chalazal end. Then,these nuclei divide at their respective ends and redivide to form an $8$-nucleate stage. As a result,there are four nuclei at each end,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 nuclei (one from the micropylar and one from 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 $8$ nuclei.

(N/A) The gynoecium represents the female reproductive part of the flower.
The gynoecium may consist of a single pistil (monocarpellary) or may have more than one pistil (multicarpellary).
When there is more than one,the pistils may be fused together (syncarpous) or may be free (apocarpous).
Each pistil has three parts: the stigma,style,and ovary.
Stigma: The stigma serves as a landing platform for pollen grains.
Style: The style is the elongated slender part beneath the stigma.
Ovary: The basal bulged part of the pistil is the ovary.
Placenta: It is located inside the ovarian cavity. Arising from the placenta are the megasporangia,commonly called ovules. The number of ovules in an ovary may be one (e.g.,wheat,paddy,mango) to many (e.g.,papaya,watermelon,orchids).

(N/A) The ovule is a small structure attached to the placenta by means of a stalk called funicle.
The body of the ovule fuses with the funicle in the region called hilum. Thus,the hilum represents the junction between the ovule and the funicle.
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.
Opposite the micropylar end is the chalaza,representing the basal part of the ovule.
Enclosed within the integuments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials.
Located in the nucellus is the embryo sac or female gametophyte. An ovule generally has a single embryo sac formed from a megaspore.
Megasporogenesis: The process of formation of megaspores from the megaspore mother cell is called megasporogenesis.

(N/A) The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles,forming the $2$-nucleate embryo sac.
Two more sequential mitotic nuclear divisions result in the formation of the $4$-nucleate and later $8$-nucleate stages of the embryo sac. These mitotic divisions are strictly free-nuclear,meaning nuclear divisions are not followed immediately by cell wall formation.
After the $8$-nucleate stage,cell walls are laid down,leading to the organization of the typical female gametophyte or embryo sac.
Six of the eight nuclei are surrounded by cell walls and organized into cells; the remaining two nuclei,called polar nuclei,are situated below the egg apparatus in the large central cell. There is a characteristic distribution of the cells within the embryo sac.
Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus,in turn,consists of two synergids and one egg cell.
The synergids have special cellular thickenings at the micropylar tip called the filiform apparatus,which play an important role in guiding the pollen tubes into the synergid.
Three cells are at the chalazal end and are called the antipodals.
The large central cell,as mentioned,has two polar nuclei.
Thus,a typical angiosperm embryo sac,at maturity,although $8$-nucleate,is $7$-celled.
Panchanan Maheshwari has classified the female gametophyte into monosporic,bisporic,and tetrasporic embryo sacs based on how many megaspores take part in the development of the embryo sac.

(N/A) $(1)$ The nutritive layer is the innermost layer of the microsporangium,known as the tapetum. It consists of cells with dense cytoplasm and generally more than one nucleus,providing nourishment to the developing pollen grains.
$(2)$ The funicle is the stalk by which the ovule is attached to the placenta within the ovary.

(N/A) $(1)$ The integuments encircle the nucellus except at the tip,where a small opening called the micropyle is organized.
$(2)$ Opposite the micropylar end lies the chalaza,which represents the basal part of the ovule.

(N/A) In some seeds, such as black pepper and beet, remnants of the nucellus are persistent. This residual, persistent nucellus is known as the $Perisperm$.
Opposite the micropylar end is the $Chalaza$, which represents the basal part of the ovule.

(N/A) The $nucellus$ is a mass of cells enclosed within the integuments of an ovule. These cells contain abundant reserve food materials, which provide nourishment to the developing embryo sac.
The $funicle$ is a stalk-like structure by which the ovule is attached to the placenta of the ovary.

(N/A) $1$. Embryo sac: The embryo sac,also known as the female gametophyte,is located within the nucellus of the ovule. It is the structure where the egg cell is produced and fertilization occurs.
$2$. Monosporic development: This is a type of embryo sac formation where the female gametophyte develops from a single functional megaspore,while the other three megaspores degenerate. This is the most common type of development in angiosperms.

(N/A) In an ovule,three cells grouped together at the micropylar end constitute the egg apparatus.
The egg apparatus consists of two synergids and one egg cell.
The synergids have special cellular thickenings at the micropylar tip called the filiform apparatus,which guide the entry of the pollen tube into the synergid.

(N/A) $(1)$ Location: The basal swollen part of the pistil.
Function: Ovules develop from the ovary.
$(2)$ Location: It is located inside the ovarian cavity.
Function: Megasporangia (ovules) develop from the placenta.

(A) $1.$ Nucellus:
Location: It is the central mass of tissue enclosed within the integuments of the ovule.
Function: It contains abundant reserve food material and provides nutrition to the developing embryo sac.
$2.$ Filiform apparatus:
Location: It consists of special cellular thickenings at the micropylar end of the synergids.
Function: It plays a crucial role in guiding the entry of the pollen tube into the synergids.

(A) The egg apparatus, located at the micropylar end of the embryo sac, consists of three cells: two $synergids$ and one $egg$ $cell$.
$1$. The $synergids$ are specialized cells that guide the pollen tube towards the egg cell.
$2$. The $egg$ $cell$ is the female gamete that fuses with the male gamete during fertilization.
$3$. The $synergids$ also possess a special cellular thickening at the micropylar tip known as the $filiform$ $apparatus$, which plays a crucial role in guiding the pollen tube into the synergid.

(N/A) mature embryo sac is $8-$ nucleate and $7-$ celled.
$1$. $3$ cells are grouped at the chalazal end and are called antipodals.
$2$. $3$ cells are grouped at the micropylar end,which constitute the egg apparatus (one egg cell and two synergids).
$3$. The large central cell contains two polar nuclei,which eventually fuse to form a diploid secondary nucleus.
Thus,the arrangement is $3+2+3$ nuclei,resulting in $7$ cells ($3$ antipodals + $1$ central cell + $2$ synergids + $1$ egg cell).

(N/A) mature angiosperm embryo sac is typically $8$-nucleate and $7$-celled.
$1$. Egg Apparatus: Located at the micropylar end,it consists of two synergids and one egg cell.
$2$. Antipodal Cells: Three cells located at the chalazal end are called antipodals.
$3$. Central Cell: The large central cell contains two polar nuclei,which eventually fuse to form a diploid secondary nucleus.
Role of Synergids: Synergids possess special cellular thickenings at the micropylar tip called the filiform apparatus. This apparatus plays a crucial role in guiding the pollen tube into the synergid.

(N/A) typical angiosperm ovule (megasporangium) consists of the following parts:
$1$. Funicle: The stalk that attaches the ovule to the placenta.
$2$. Hilum: The junction point between the ovule and the funicle.
$3$. Integuments: Protective envelopes surrounding the nucellus.
$4$. Micropyle: $A$ small opening at the tip of the integuments.
$5$. Chalaza: The basal part of the ovule representing the origin of integuments.
$6$. Nucellus: The central mass of cells containing food reserves.
$7$. Embryo sac: The female gametophyte located within the nucellus.

(A) The correct matching is as follows:
$(a)$ Sex cell of the embryo sac is the $(3)$ Egg cell.
$(b)$ Synergid cells are the $(1)$ Synergid cells present in the embryo sac.
$(c)$ Cells opposite to the micropyle are the $(2)$ Antipodal cells.
$(d)$ The $(4)$ Secondary nucleus is located within the central cell of the embryo sac.
Therefore, the correct sequence is $(a-3), (b-1), (c-2), (d-4)$.

(A) The ovule is attached to the placenta by means of a stalk called the funicle. The point of attachment of the body of the ovule with the funicle is known as the hilum. Thus,the hilum represents the junction between the ovule and the funicle.

(B) The flower is the reproductive unit of angiosperms. The female reproductive part of the flower is called the $Pistil$ or $Gynoecium$.
The $Pistil$ consists of three main parts: the $Stigma$,the $Style$,and the $Ovary$.
The $Ovary$ is the enlarged basal part of the $Pistil$ that contains the ovules.
Therefore,the $Ovary$ is a part of the $Pistil$.

(D) The pistil or gynoecium is the female reproductive part of a flower. It consists of three main parts:
$1$. $Stigma$: The landing platform for pollen grains.
$2$. $Style$: The elongated slender part beneath the stigma.
$3$. $Ovary$: The enlarged basal part containing the ovules.
The $Connective$ is a sterile tissue that connects the two lobes of an anther in the stamen (the male reproductive part). Therefore, it is not a part of the pistil.

(C) In a flower, the reproductive organs are categorized as follows:
$1$. The $Androecium$ (stamen) is the male reproductive organ.
$2$. The $Gynoecium$ (pistil or carpel) is the female reproductive organ.
$3$. The $Calyx$ (sepals) and $Corolla$ (petals) are accessory whorls involved in protection and attraction, respectively.
Therefore, the $Gynoecium$ represents the female reproductive part.

(A) The term 'monocarpellary' is derived from 'mono' meaning one and 'carpellary' referring to the carpel or pistil. Therefore,a monocarpellary gynoecium consists of exactly $1$ pistil.