Embryo Questions in English

(A) In sexual reproduction,the fusion of male and female gametes results in the formation of a diploid cell called the $Zygote$.
Following fertilization,the $Zygote$ undergoes repeated mitotic divisions to develop into an $Embryo$.
In flowering plants,the $Ovule$ develops into a $Seed$,and the $Ovary$ develops into a $Fruit$.

(A) Embryogenesis refers to the development of an embryo from the zygote. During embryogenesis,the zygote undergoes cell division $(mitosis)$ and cell differentiation. The cell division of the zygote is called cleavage.

(D) Embryogenesis refers to the development of an embryo from the zygote.
During this process,the zygote undergoes cell division (mitosis) to increase the number of cells.
Simultaneously,the cells undergo cell differentiation to form specialized tissues and organs for the developing organism.
Meiosis does not occur during embryogenesis as the zygote is already diploid $(2n)$ and needs to maintain this ploidy level in the somatic cells of the embryo.
Therefore,both cell division (mitosis) and cell differentiation are essential processes in embryogenesis.

(D) In a mature seed,the embryo represents the young sporophyte of the next generation.
It is formed by the fusion of male and female gametes (fertilization) resulting in a zygote,which then develops into the embryo.
Therefore,the embryo acts as the progenitor of the next generation plant.

(D) Embryos of monocotyledons possess only one cotyledon.
In the grass family,the cotyledon is called the scutellum,which is situated toward one side (lateral) of the embryonal axis.
At its lower end,the embryonal axis has the radicle and root cap enclosed in an undifferentiated sheath called the coleorhiza.
The portion of the embryonal axis above the level of attachment of the scutellum is the epicotyl.
Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow structure called the coleoptile.

(D) The diagram shows a typical dicot embryo with its various important parts. $A$ typical dicotyledonous embryo consists of an embryonal axis and two cotyledons.
$1$. The portion of the embryonal axis above the level of cotyledons is the epicotyl, which terminates with the plumule or stem tip.
$2$. The cylindrical portion below the level of cotyledons is the hypocotyl, which terminates at its lower end in the radicle or root tip.
$3$. The root tip is covered with a root cap.
Based on the provided diagram, the labels correspond to: $A-Plumule, B-Cotyledons, C-Hypocotyl, D-Radicle, E-Root cap$.

(A) In monocotyledonous seeds,the embryo consists of a single cotyledon.
This single cotyledon is called the $Scutellum$.
It is situated towards one side (lateral) of the embryonal axis.
Therefore,the correct description is that it is a $Scutellum$ which is lateral in position.

(B) In a dicotyledonous embryo,the embryonal axis consists of two parts separated by the level of attachment of cotyledons.
$1$. The portion of the embryonal axis above the level of cotyledons is called the $Epicotyl$,which terminates with the $Plumule$ (stem tip).
$2$. The cylindrical portion below the level of cotyledons is called the $Hypocotyl$,which terminates at its lower end in the $Radicle$ or root tip.
Therefore,the correct answer is $Hypocotyl$.

(C) The provided figure represents a developing dicot embryo.
Based on the anatomical structure:
$a$ points to the suspensor,which anchors the embryo to the endosperm.
$b$ points to the plumule (embryonic shoot).
$c$ points to the cotyledons (seed leaves).
$d$ points to the radicle (embryonic root).
Therefore,the correct identification is $a$: Suspensor,$b$: Plumule,$c$: Cotyledons,$d$: Radicle.
This corresponds to option $C$.

(A) The provided figure represents the longitudinal section of a monocot embryo (specifically a grass embryo).
- Part $a$ points to the protective sheath covering the plumule,known as the Coleoptile.
- Part $b$ points to the shield-shaped cotyledon,known as the Scutellum.
- Part $c$ points to the embryonic root,known as the Radicle.
- Part $d$ points to the undifferentiated sheath covering the radicle,known as the Coleorrhiza.
Therefore,the correct sequence is $a$: Coleoptile,$b$: Scutellum,$c$: Radicle,$d$: Coleorrhiza.

(A) In dicot embryogeny,the zygote undergoes a transverse division to form a terminal cell (embryonal cell) and a basal cell.
The terminal cell undergoes two vertical divisions at right angles to each other,followed by one transverse division,resulting in an eight-celled stage known as the octant stage.
These eight cells are arranged in two tiers: the upper four cells form the epibasal tier (which gives rise to plumule and cotyledons),and the lower four cells form the hypobasal tier (which gives rise to the hypocotyl and radicle).
Thus,both the Assertion and the Reason are correct,and the Reason correctly explains the arrangement of the cells formed in the octant stage.

(A) In Crucifer-type (or Onagrad-type) embryo development,the zygote divides to form a terminal cell and a basal cell.
The terminal cell forms the octant embryo,which differentiates into the plumule and the hypocotyl.
The basal cell forms the suspensor,and the cell of the suspensor adjacent to the embryo proper is called the hypophysis.
The hypophysis undergoes divisions to form the root cap and the tip of the radicle.
Therefore,the hypo-basal tier of the octant embryo does not produce the complete radicle,as the tip is derived from the hypophysis.
Both statements are correct and the Reason explains why the hypo-basal tier does not produce the complete radicle.

(A) In monocotyledonous seeds,such as maize,the embryo consists of one large and shield-shaped cotyledon known as the $scutellum$.
It is situated towards one side (lateral) of the embryonic axis.
Therefore,the scutellum is a cotyledon.

(A) In sexual reproduction,the fusion of male and female gametes results in the formation of a diploid cell called the $Zygote$.
Following fertilization,the $Zygote$ undergoes repeated mitotic divisions to develop into an embryo.
Therefore,the embryo is derived directly from the $Zygote$.

(B) In dicotyledonous plants,the zygote undergoes a series of divisions to form the embryo. The developmental stages are as follows:
$1$. The zygote divides to form the proembryo.
$2$. The proembryo further develops into a globular embryo.
$3$. The globular embryo then differentiates into a heart-shaped embryo.
$4$. Finally,it matures into a fully developed embryo with cotyledons and an embryonal axis.
Therefore,the correct sequence is: Proembryo $\rightarrow$ Globular embryo $\rightarrow$ Heart-shaped embryo $\rightarrow$ Mature embryo.

(B) In angiosperms,the development of the embryo (embryogeny) occurs from the zygote.
$1$. The zygote is formed by the fusion of the male gamete and the egg cell,resulting in a diploid $(2n)$ structure located near the micropylar end of the embryo sac.
$2$. The early stages of embryogeny are identical in both monocots and dicots (proembryo,globular,and heart-shaped stages).
$3$. Crucially,the development of the endosperm precedes the development of the embryo. This is an evolutionary adaptation to ensure that nutrition is available for the developing embryo.
$4$. Therefore,the statement that the embryo is formed before the endosperm is incorrect.

(A) In a typical dicot embryo,the structure consists of an embryonal axis and two cotyledons.
- $P$ represents the plumule,which is the embryonic shoot tip.
- $Q$ represents the cotyledons.
- $R$ represents the hypocotyl.
- $S$ represents the radicle,which is the embryonic root tip.
Therefore,the plumule is represented by $P$.

(B) In the longitudinal section of a grass embryo (e.g.,maize):
$1$. $P$ represents the Scutellum,which is a large,shield-shaped cotyledon.
$2$. $Q$ represents the Shoot apex,which is enclosed in a foliar structure called the coleoptile.
$3$. $R$ represents the Root cap,which protects the radicle at the base of the embryo.
Therefore,the correct identification is $P$: Scutellum,$Q$: Shoot apex,$R$: Root cap.

(B) In monocotyledonous seeds,such as those of the grass family (Poaceae),the single cotyledon is known as the scutellum. It is shield-shaped and situated towards one side (lateral) of the embryonal axis. Its primary function is to absorb nutrients from the endosperm and transfer them to the developing embryo.

(A) In the embryo of a monocotyledon (e.g.,grass),the root cap is covered by an undifferentiated sheath known as the $P = \text{Coleorhiza}$.
The shoot apex and a few leaf primordia enclosed in a hollow foliar structure are known as the $Q = \text{Coleoptile}$.
Therefore,the correct sequence is $P = \text{Coleorhiza}$ and $Q = \text{Coleoptile}$.

(C) The given image represents the structure of a monocot embryo (specifically a grass embryo).
In this structure:
$P$ represents the pericarp/seed coat.
$Q$ represents the endosperm.
$R$ represents the scutellum,which is the single cotyledon in monocots.
$S$ represents the coleoptile or the embryonic axis.
Therefore,the cotyledon is represented by $R$.

(D) During the development of a dicot embryo,the zygote divides to form a proembryo and a suspensor.
The terminal cell of the suspensor,which is in contact with the embryo proper,is known as the $hypophysis$.
This $hypophysis$ cell undergoes further divisions to give rise to the radicle and the root cap of the developing embryo.

(B) In angiosperms,the process of fertilization involves the fusion of a male gamete with the egg cell to form a zygote.
This zygote is located at the micropylar end of the embryo sac.
Following fertilization,the zygote undergoes mitotic divisions to develop into an embryo.
Therefore,the development of the embryo occurs at the micropylar end of the embryo sac.

(B) In the development of a dicot embryo,the zygote undergoes a transverse division to form a large basal cell and a small terminal cell (also called the embryonal initial).
$1$. The large basal cell acts as the suspensor initial $(a-i)$.
$2$. The small terminal cell is the embryonal initial $(b-iv)$.
$3$. The suspensor is formed from the basal cell. The first cell of the suspensor towards the micropylar end often enlarges to form a haustorium $(c-ii)$.
$4$. The lowermost cell of the suspensor,which is in contact with the embryonal mass,is called the hypophysis $(d-iii)$.
Therefore,the correct matching is $a-i, b-iv, c-ii, d-iii$.

(D) In a $2$-celled pro-embryo,the larger cell towards the micropyle is called the suspensor or basal cell.
The smaller cell towards the chalazal end is the terminal or embryonal cell.
This terminal cell undergoes one transverse and two vertical mitotic divisions to form the $8$-celled octant stage.

(D) The embryonal initial undergoes $3$ successive mitotic divisions to form an $8$-celled stage known as the octant.
Further development leads to the formation of a globular embryo.
As the embryo continues to grow,the enlargement of the hypocotyl and cotyledons results in the formation of a heart-shaped structure.
Finally,the embryo matures into a horse shoe-shaped structure.

(A) In angiosperms,the zygote (also known as the oospore) undergoes a transverse division to form two cells: a larger basal cell and a smaller terminal cell (or apical cell).
The basal cell undergoes further transverse divisions to form a filamentous structure called the suspensor.
The suspensor helps in pushing the developing embryo into the endosperm for nutrition.
Therefore,the suspensor cells develop from the oospore (zygote).

(A) In the development of a dicot embryo,the zygote undergoes a transverse division to form two cells: a larger basal cell and a smaller terminal (or apical) cell.
The basal cell undergoes repeated transverse divisions to form a filamentous structure known as the suspensor.
The suspensor helps in pushing the embryo into the endosperm for nutrition.
The terminal cell undergoes further divisions to form the embryo proper (radicle,plumule,and cotyledons).

(D) The provided diagram represents the structure of a dicot embryo. In this structure, the lower pointed portion is the radicle, which is covered by a protective sheath-like structure at the tip known as the root cap. Therefore, "$X$" represents the radicle and "$Y$" represents the root cap. Thus, the correct option is $D$.

(D) In flowering plants,the life cycle involves an alternation of generations between the haploid gametophyte and the diploid sporophyte.
$A$. Pollen grains are haploid $(n)$ structures produced by meiosis.
$B$. The egg cell is a haploid $(n)$ female gamete.
$C$. The male gamete is a haploid $(n)$ cell.
$D$. The zygote is formed by the fusion of the male and female gametes $(n + n)$,resulting in a diploid $(2n)$ cell.
Therefore,the zygote is the diploid structure.

(A) Based on the standard diagram of the $L$.$S$. of a grass embryo (monocot embryo) as provided in the $NCERT$ textbook:
- $A$ represents the Epiblast (the small,rudimentary second cotyledon).
- $B$ represents the Radicle (the embryonic root).
- $C$ represents the Coleoptile (the protective sheath covering the plumule).
- $D$ represents the Scutellum (the large,shield-shaped cotyledon).
- The structure covering the radicle is the Coleorrhiza.
- The top portion represents the Shoot apex (plumule).
Comparing these labels with the given options,option $A$ provides the correct identification for the parts labeled in the standard diagram of a grass embryo.