Meristematic Tissue Questions in English

(A) The Histogen theory,proposed by Hanstein,suggests that the plant body is derived from three distinct layers of meristematic cells called histogens: dermatogen,periblem,and plerome.
This theory is considered more applicable and accurate for the root apex,where these three distinct zones can be clearly identified and traced to their respective mature tissues.
In the shoot apex,the organization is more complex and does not strictly follow the three-layered histogen pattern as clearly as it does in the root.

(D) According to the Histogen theory proposed by Hanstein,the root apex consists of three distinct meristematic zones:
$1$. Dermatogen: The outermost layer,which gives rise to the epidermis.
$2$. Periblem: The middle layer,which gives rise to the cortex and endodermis.
$3$. Plerome: The central core,which gives rise to the stele,including the vascular tissues (xylem and phloem) and the pith.
Therefore,the vascular tissue is derived from the plerome.

(B) The primary meristem responsible for the growth of the root is the $Apical \text{ meristem}$.
It is located at the root tip and is responsible for the primary growth of the plant by increasing the length of the root.
Cambium, vascular cambium, and phellogen are examples of secondary or lateral meristems involved in secondary growth.

(C) The $Tunica-Corpus$ theory explains the organization of the shoot apical meristem.
In the $Tunica$ layer,the cells undergo anticlinal divisions,which increase the surface area of the organ.
In the $Corpus$ region,the cells undergo divisions in various planes (including periclinal),which contribute to the increase in the volume or mass of the organ.
Therefore,they differ primarily in their plane of division.

(A) According to the Tunica-Corpus theory,the shoot apical meristem is organized into two layers: the tunica and the corpus.
The tunica consists of one or more peripheral layers of cells that divide only by anticlinal divisions.
Anticlinal divisions occur in a plane perpendicular to the surface,which increases the surface area of the layer without increasing its thickness.
Therefore,the tunica divides in only one plane (anticlinal plane).

(A) The $Tunica$ layer of the shoot apical meristem is characterized by anticlinal divisions only.
These divisions increase the surface area of the meristem without increasing the number of layers.
Because the cells divide in a single plane (anticlinal),they maintain the integrity of the outer layer,which is a defining feature of the $Tunica$ layer in the $Tunica-Corpus$ theory.

(B) Anticlinal divisions are cell divisions that occur perpendicular to the surface of the organ.
These divisions increase the number of cells in the surface layer,thereby increasing the surface area of the organ.
This type of division is responsible for the lateral expansion or increase in the area of tissues like the epidermis or the cortex.

(D) Periclinal division is a type of cell division where the plane of division is parallel to the surface or the circumference of the organ. This results in an increase in the number of cell layers. Therefore,it is also known as tangential division.

(A) The $Tunica$ $Corpus$ theory,proposed by $Schmidt$ $(1924)$,explains the organization of the shoot apical meristem in angiosperms.
According to this theory,the shoot apex consists of two distinct zones: the $Tunica$ and the $Corpus$.
The $Tunica$ is the peripheral layer$(s)$ of the meristem that undergoes anticlinal divisions,resulting in an increase in surface area.
These layers eventually differentiate into the $Epidermis$ of the plant body.

(B) The $Korper-Kappe$ theory was proposed by $Schuepp$ in $1917$ to explain the organization and development of the root apical meristem.
According to this theory, the root apex consists of two parts: the $Korper$ (body) and the $Kappe$ (cap).
The $Korper$ represents the central part of the root apex, while the $Kappe$ represents the root cap region.
Therefore, this theory is specifically applicable to the root apex.

(B) The $Korper-Kappe$ theory was proposed by $Schuepp$ in $1917$.
This theory describes the organization of the root apical meristem.
It is comparable to the $tunica-corpus$ theory of the shoot apex.
In German, $Korper$ means body and $kappe$ means cap.

(C) According to the Tunica-Corpus theory proposed by Schmidt $(1924)$ and further elaborated by Popham and Chan $(1950)$,the shoot apical meristem of angiosperms is organized into two distinct regions: the tunica and the corpus.
The corpus is the central core of the apical meristem,which is characterized by cells that divide in various planes,leading to an increase in the volume of the tissue.
Popham identified that the corpus in a normal angiospermous shoot apex is composed of three distinct zones: the central zone,the peripheral zone,and the pith rib meristem.

(C) The $tunica-corpus$ theory,proposed by $Schmidt$ in $1924$,explains the organization of the shoot apical meristem in angiosperms.
According to this theory,the shoot apex is differentiated into two distinct layers: the $tunica$ (outer layer) and the $corpus$ (inner mass).
This differentiation is characteristic of angiosperms.
In contrast,the shoot apices of pteridophytes do not show this $tunica-corpus$ organization; instead,they typically possess a single apical cell or a group of initial cells that do not differentiate into these specific layers.

(B) Primary growth in plants refers to the increase in length of the plant body,which occurs due to the activity of primary meristems.
Promeristem (or promeristematic tissue) represents the earliest stage of meristematic cells located at the tips of roots and shoots.
These cells divide actively to produce the primary tissues of the plant body,thereby contributing to primary growth.
Lateral meristems (like vascular cambium and cork cambium) are responsible for secondary growth,which involves an increase in the girth or thickness of the plant.

(C) promeristem is the earliest or youngest stage of meristematic tissue found at the tips of shoots and roots. It is the embryonic meristem that gives rise to other primary meristems,such as the protoderm,procambium,and ground meristem,which eventually differentiate into permanent tissues.

(C) The protoderm is the outermost layer of the apical meristem,which is a part of the promeristem. The promeristem is the earliest stage of meristematic tissue that gives rise to primary meristems,including the protoderm (which forms the epidermis),procambium (which forms vascular tissues),and ground meristem (which forms the ground tissue). Therefore,the correct option is $(c)$.

(B) The $Promeristem$ (also known as primordial meristem) is the earliest stage of meristematic tissue found at the tips of shoots and roots.
It is the region from which all primary permanent tissues, including the $procambium$, $protoderm$, and $ground$ $\text{meristem}$, originate.
The $procambium$ subsequently gives rise to the primary vascular tissues (xylem and phloem).

(B) The terms 'protoderm','procambium',and 'ground meristem' were coined by Johannes von Hanstein in $1868$ to describe the three primary meristems found at the shoot apex of plants.
- Protoderm gives rise to the epidermis.
- Procambium gives rise to the vascular tissues (xylem and phloem).
- Ground meristem gives rise to the ground tissue system (cortex,pith,etc.).
Therefore,the correct answer is $B$.

(D) Primary meristems are those that appear early in the life of a plant and contribute to the formation of the primary plant body.
$1$. $Protoderm$ is the outermost primary meristem that gives rise to the epidermis.
$2$. $Pleurome$ is the central part of the apical meristem that gives rise to the stele.
$3$. $Intercalary$ $meristem$ is a type of primary meristem found between permanent tissues,responsible for the elongation of internodes.
Since all these are involved in the primary growth of the plant,the correct option is $D$.

(A) Primary meristems are responsible for the primary growth of plants and include protoderm,ground meristem,and procambium.
$A$. Protoderm gives rise to the epidermis.
$B$. Ground meristem gives rise to the ground tissue system.
$C$. Procambium gives rise to the primary vascular tissues.
$D$. Endodermis is a layer of cells that differentiates from the ground meristem and is composed of permanent tissue,not meristematic tissue.

(C) Secondary meristems are those meristems that develop from mature permanent tissues through the process of dedifferentiation.
These tissues regain the capacity to divide,which they had previously lost.
Examples include the interfascicular cambium and the cork cambium (phellogen).
Therefore,the correct option is $C$.

(B) The repair of injured plant parts is primarily facilitated by the activity of $Lateral$ $meristem$ (also known as secondary meristem).
$Lateral$ $meristem$ includes the vascular cambium and cork cambium,which are responsible for secondary growth in plants.
When a plant is injured,these meristematic cells undergo rapid division to form new tissues,such as callus or wound periderm,to heal the damaged area.

(C) The $Quiescent$ centre is a region of cells located at the root apex, specifically between the root cap and the active meristematic zone.
These cells are characterized by a very low rate of division or are metabolically inactive compared to the surrounding highly meristematic cells.
This region acts as a reservoir of cells that can resume division if the primary meristematic cells are damaged.

(B) The quiescent zone is a region located in the root apical meristem where the cells are characterized by very low mitotic activity.
Because these cells are not actively dividing,they remain in the $G_1$ phase of the cell cycle for an extended period.
Consequently,the $DNA$ content in these cells is low compared to actively dividing meristematic cells that undergo $DNA$ replication ($S$ phase) frequently.

(B) According to the histogen theory proposed by Hanstein,the root and shoot apices consist of three distinct meristematic zones or histogens:
$1$. $Dermatogen$: The outermost layer that gives rise to the epidermis (dermal tissue).
$2$. $Periblem$: The middle layer that gives rise to the cortex.
$3$. $Plerome$: The central core that gives rise to the stele (vascular tissue).
Therefore,the correct option is $B$.

(C) The Histogen theory,proposed by $Hanstein$,suggests that the root and shoot apices consist of three distinct zones or histogens: $Dermatogen$,$Periblem$,and $Plerome$.
$1$. $Dermatogen$: The outermost layer,which gives rise to the epidermis.
$2$. $Periblem$: The middle layer,which gives rise to the cortex and endodermis.
$3$. $Plerome$: The innermost central core,which gives rise to the stele,including the vascular bundles and pith.

(A) According to the Histogen theory proposed by Hanstein,the apical meristem of the shoot consists of three distinct layers:
$1$. $Dermatogen$: The outermost layer that gives rise to the epidermis.
$2$. $Periblem$: The middle layer that develops into the cortex.
$3$. $Plerome$: The central core that forms the stele (vascular tissues and pith).
Therefore,the $Dermatogen$ is the layer responsible for forming the epidermal tissues.

(C) Promeristem is the earliest stage of meristematic tissue found in the growing tips of roots and shoots.
It differentiates to form the primary meristem,which includes the protoderm,procambium,and ground meristem.
These primary meristems eventually give rise to the primary permanent tissues of the plant body.

(C) . $Cambium$ represents the lateral meristem of a plant,which consists of actively dividing cells responsible for secondary growth.

(D) The $Procambium$ is a type of primary meristematic tissue derived from the apical meristem.
It is responsible for the development of primary vascular tissues, specifically primary $xylem$ and primary $phloem$, within the plant body.
$Protonema$ is a developmental stage in mosses, $Promeristem$ refers to the earliest stage of meristematic cells at the apex, and $Ground meristem$ gives rise to the ground tissue system (cortex, pith, etc.).
Therefore, the correct option is $D$.

(C) Lateral meristem is located on the lateral sides of the stem and root. It divides mainly periclinally or radially,which results in an increase in the girth or diameter of the plant organ. This process is known as secondary growth,which leads to growth in thickness.

(B) The correct answer is $B$. When a wound occurs in a plant,the healthy cells adjacent to the wound site undergo rapid division to form a mass of undifferentiated parenchymatous cells known as $Callus$. This $Callus$ tissue grows over the injured area,effectively covering and sealing the wound,which facilitates the healing process.

(B) $Intercalary$ meristem is a type of primary meristem that is found between permanent tissues. It is responsible for the elongation of internodes and the growth of leaves,which are components of primary growth. It is essentially a portion of the apical meristem that gets separated by the development of permanent tissues.

(C) The correct answer is $C$.
Meristematic tissue,or meristem,consists of a group of undifferentiated cells that possess the capacity for continuous cell division.
These cells are responsible for the growth and development of the plant body by constantly producing new cells.

(D) Apical meristems are found at the tips of roots and shoots in all vascular plants.
Both Gymnosperms,Pteridophytes,and Angiosperms are vascular plants that possess apical meristems responsible for primary growth.
Therefore,all these groups utilize apical meristem for their growth and development.

(A) The root apical meristem is located at the tip of the root.
It is responsible for the primary growth of the root,leading to an increase in the length of the root system.
Therefore,the meristem of the root is classified as apical meristem.

(A) Meristems are specialized regions in plants consisting of actively dividing cells.
These cells have the capacity to undergo mitosis,which leads to the growth and development of the plant body.
Unlike permanent tissues,meristematic cells are undifferentiated and continue to divide throughout the life of the plant.

(B) The histogen theory,proposed by Hanstein,suggests that the root and shoot apices consist of distinct layers of meristematic cells called histogens. These histogens are classified based on the specific types of future tissues they give rise to. The three histogens are:
$1$. Dermatogen: Gives rise to the epidermis.
$2$. Periblem: Gives rise to the cortex.
$3$. Plerome: Gives rise to the stele (vascular cylinder).

(D) Meristematic cells are actively dividing cells found in the meristematic regions of plants.
These cells possess thin,flexible primary cell walls composed of cellulose,which facilitate rapid cell division and growth.
They are compactly arranged without any intercellular spaces between them to ensure structural integrity and efficient communication during the division process.
Therefore,the correct characteristics are thin cell walls and no intercellular spaces.

(C) The quiescent centre is a region in the root apical meristem where the cells have a very low rate of division or are inactive. It acts as a reservoir of stem cells that can resume division if the surrounding meristematic cells are damaged.

(B) According to the histogen theory proposed by Hanstein,the apical meristem consists of three distinct layers: Dermatogen,Periblem,and Plerome.
$1$. Dermatogen gives rise to the epidermis.
$2$. Periblem gives rise to the cortex and endodermis.
$3$. Plerome gives rise to the stele (pericycle,vascular bundles,and pith/medulla).
Therefore,the correct option is $B$.

(C) In the primary growth of plants,the apical meristem differentiates into three primary meristems: the protoderm,the procambium,and the ground meristem. The procambium (also known as the plerome in some terminologies) is the meristematic tissue that gives rise to the primary vascular tissues,namely the xylem and phloem,which together form the vascular bundles.

(C) The apical meristem differentiates into three primary meristems: protoderm,procambium,and ground meristem.
$1$. Protoderm gives rise to the epidermis.
$2$. Procambium gives rise to the primary vascular tissues (xylem and phloem).
$3$. Ground meristem gives rise to the ground tissue system,which includes the hypodermis,cortex,endodermis,pericycle,pith,and medullary rays.
Therefore,the pith is derived from the ground meristem.

(B) According to the Histogen theory proposed by Hanstein,the apical meristem of the root is divided into three distinct zones:
$1$. $Dermatogen$: The outermost layer that gives rise to the epidermis.
$2$. $Periblem$: The middle layer that gives rise to the cortex.
$3$. $Plerome$: The innermost central core that gives rise to the stele,which includes the vascular tissues,pericycle,and pith.
Therefore,the stelar region is derived from the $Plerome$.

(C) Active mitotic divisions occur in meristematic tissues,which are regions of continuous cell division.
$C$ Cambium is a lateral meristem responsible for secondary growth in plants.
$A$ Cortex and $B$ Pith/Pericycle are generally composed of permanent tissues (parenchyma) that have lost the ability to divide,except in specific cases like wound healing or secondary growth initiation.
Therefore,the cambium is the primary site of active mitotic division among the given options.

(B) The fascicular cambium is present within the vascular bundles of the stem.
It originates from the procambium,which is a derivative of the apical meristem.
Since it is derived from cells that have retained their meristematic activity from the embryonic stage (procambium),it is classified as a primary meristem.
It is responsible for the formation of primary vascular tissues.

(B) Undifferentiated cells are cells that have not yet specialized into a specific type of tissue. In plants,these are known as meristematic cells.
$B$ is the correct option because the cambium (specifically vascular cambium) consists of meristematic cells that remain undifferentiated and actively divide to produce secondary xylem and secondary phloem,contributing to the secondary growth of the plant.

(A) The vascular cambium is responsible for secondary growth in dicot stems and roots.
It originates from the procambium and interfascicular parenchyma.
Because it is located parallel to the longitudinal axis of the plant organ and increases the girth (diameter) of the plant,it is classified as a lateral meristem.

(A) The cambium,specifically the vascular cambium and cork cambium,is responsible for secondary growth in plants.
It is located parallel to the longitudinal axis of the plant body.
Because it increases the girth or diameter of the stem and root,it is classified as a lateral meristem.
Unlike apical and intercalary meristems,which are responsible for primary growth (increase in length),the lateral meristem is responsible for secondary growth.

(C) The quiescent centre is a region in the root apical meristem where the rate of cell division is very low. It acts as a reservoir of active initials that can replace damaged cells of the meristem,ensuring the continuous growth of the root.