Meristematic Tissue Questions in English

(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.

(A) Based on the plane of cell division,meristems are classified into three types:
$1$. Mass meristem: Division occurs in all planes,resulting in a mass of cells (e.g.,embryo,endosperm).
$2$. Plate meristem: Division occurs in two planes,resulting in a plate-like structure (e.g.,leaf lamina).
$3$. Rib (or file) meristem: Division occurs in only one plane,resulting in rows or files of cells (e.g.,root cortex).

(C) The $Tunica-Corpus$ theory,proposed by $Schmidt$ $(1924)$,explains the organization of the shoot apical meristem.
According to this theory,the shoot apex is divided into two distinct zones based on the planes of cell division:
$1$. $Tunica$: It consists of one or more peripheral layers of cells that divide primarily by anticlinal divisions,contributing to surface growth.
$2$. $Corpus$: It is the central mass of cells enclosed by the $Tunica$,where cells divide in various planes,contributing to the increase in volume.
Therefore,the organization is determined by the planes of cell division.

(A) The correct answer is $A$.
Meristematic tissues consist of actively dividing cells.
These cells require a significant amount of energy to perform continuous mitosis and cell growth.
Consequently,they exhibit the highest rate of metabolic activity and,therefore,the highest rate of respiration compared to other plant tissues.

(A) Metabolic energy is primarily required for active cell division and growth.
$(a)$ Cambium cells are meristematic in nature,meaning they are constantly dividing to produce new cells for secondary growth.
$(b)$ Cork cells are dead at maturity and provide protection.
$(c)$ Xylem cells (tracheids and vessels) are mostly dead at maturity and serve in water conduction.
$(d)$ Root parenchyma cells are mature,differentiated cells that primarily function in storage and are less metabolically active compared to meristematic tissues.
Therefore,the cambium utilizes the most metabolic energy.

(D) Active cell division in plants occurs primarily in meristematic tissues.
Apical meristems are located at the tips of roots and shoots.
These regions contain cells that are constantly dividing to facilitate the primary growth of the plant.
Therefore,the correct location to observe active cell division is at the tip of the root and shoot.

(A) . Apical meristems are found at the shoot and root apex.
As a result of the activity of these meristems,plants increase in length.

(C) The term "Cytochimeras" refers to organisms or tissues that contain cells with different chromosomal constitutions (ploidy levels or genetic makeup) within the same individual.
In plant biology, this often occurs due to mutations or irregular cell divisions in the meristematic regions.
Therefore, option $C$ is the correct answer as it describes cells having different chromosomal characteristics compared to other vegetative cells in the same organism.

(B) In vascular plants,apical dominance is a common phenomenon where the apical meristem inhibits the growth of lateral buds.
This is primarily mediated by the hormone $Auxin$,which is synthesized in the apical meristem and transported downwards.
When the grass is mowed,the apical meristem (the source of $Auxin$) is removed,which eliminates apical dominance.
This removal stimulates the activity of the $intercalary$ $meristem$,leading to rapid growth and a well-maintained,dense lawn.

(A) Respiration is a metabolic process that provides energy for cellular activities.
Meristematic tissues consist of actively dividing cells that require a significant amount of energy for mitosis,$DNA$ replication,and the synthesis of new cellular components.
Due to this high metabolic demand,meristematic tissues exhibit the highest rate of respiration compared to other plant tissues like parenchyma or mechanical tissues,which are often more mature or specialized.

(B) Cyclin proteins are regulatory proteins that control the progression of the cell cycle by activating cyclin-dependent kinases $(CDKs)$.
Since the cell cycle involves active division,cyclin synthesis is primarily associated with cells that are actively dividing.
Meristematic tissues consist of cells that are in a continuous state of division $(mitosis)$.
Permanent tissues and lignified cells are typically in the $G_0$ phase or are terminally differentiated and do not undergo the cell cycle; thus,they do not synthesize cyclins for division.
Therefore,the synthesis of cyclin proteins occurs in meristematic tissues.

(C) In plants,during the embryonic stage,the growth is not uniform across all cells. The meristematic activity,which is responsible for continuous cell division and growth,is restricted to a specific group of cells located at the tips of the embryo,known as the apical meristems. Therefore,the correct answer is a group of apical cells.

(A) Plate meristem is a type of meristematic tissue where cells divide by anticlinal divisions in two planes at right angles to each other. This type of division results in the formation of a plate-like structure,which increases the surface area of the organ (e.g.,leaf lamina). Therefore,the correct answer is $A$.

(A) According to the Histogen theory proposed by Hanstein,the apical meristem of the root consists of three distinct zones or histogens:
$1$. $Dermatogen$: The outermost layer that gives rise to the epidermis.
$2$. $Periblem$: The middle layer that gives rise to the cortex.
$3$. $Plerome$: The central core that gives rise to the vascular tissue (xylem and phloem) and the pith.
Therefore,the vascular tissue develops from the $Plerome$.

(C) The growth of the leaf lamina occurs due to the activity of the $Marginal \ meristem$.
This meristem is located at the margins of the leaf primordia and is responsible for the expansion of the leaf blade in terms of width and surface area.
Therefore,the correct option is $C$.

(C) In the development of primary xylem,the first-formed xylem elements are called protoxylem. During the early stages of plant growth,when the root or stem undergoes $elongation$,the conducting elements of the protoxylem,which have annular and spiral thickenings,are formed. These types of thickenings allow the xylem vessels to stretch as the organ grows in length. As the organ matures and stops elongating,metaxylem with more complex thickenings (like pitted or reticulate) develops.

(B) Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism.
In plants, $Meristematic \text{ } tissue$ consists of undifferentiated, actively dividing cells.
These cells have the highest capacity to undergo mitosis and differentiate into various types of tissues, thus exhibiting the highest degree of totipotency.
Tracheids, cork, and sieve tubes are examples of permanent tissues that have lost the ability to divide.

(C) In the embryonic stage,the cells of a plant are actively dividing to form various tissues and organs. These actively dividing cells are known as $Meristematic$ cells. They possess the ability to undergo mitosis,which is essential for the growth and development of the plant body.

(B) The quiescent center is a region in the root apical meristem where the cells have a very low rate of division. These cells are characterized by having a light cytoplasm and small nuclei,which distinguishes them from the actively dividing cells of the surrounding meristematic regions. They serve as a reservoir of cells that can replace damaged meristematic cells.

(C) The growth of the stem in monocots like sugarcane is primarily due to the activity of the intercalary meristem.
Intercalary meristems are located between permanent tissues and are responsible for the elongation of internodes.
Since the activity of these meristems varies at different nodes,the length of the internodes in the sugarcane stem is variable.

(D) The apical meristem is a type of meristematic tissue responsible for the primary growth of plants. It is located at the tips of both the shoot and the root. In the context of roots,the root apical meristem is responsible for the elongation of the root system. Since all types of roots (radicle,taproot,and adventitious roots) possess a growing tip,the apical meristem is present in all of them.

(C) The Quiescent Center theory was proposed by $Clowes$ in $1954$.
It describes a region of inactive or slowly dividing cells located at the root apical meristem,situated between the root cap and the active meristematic region.
These cells act as a reservoir of cells that can resume division if the primary meristematic cells are damaged.

(D) Apical meristems are the meristematic tissues responsible for primary growth in plants.
They are located at the growing tips of the plant body.
Specifically,they are found at the root tips (root apical meristem) and shoot tips (shoot apical meristem).
Axillary buds are also derived from the shoot apical meristem and contain meristematic cells capable of forming branches or flowers.
Therefore,all the given options are correct locations for apical meristematic activity.

(A) The $Tunica-Corpus$ theory was proposed by $Schmidt$ in $1924$. This theory explains the organization of the shoot apical meristem in angiosperms. According to this theory,the shoot apex consists of two distinct regions: the $Tunica$ (peripheral layer) and the $Corpus$ (central mass).

(C) The shoot apex (apical meristem) is protected by the developing leaf primordia.
Leaf primordia are small,immature leaves that grow around the shoot apical meristem to shield it from mechanical injury and desiccation as it grows.

(D) Meristematic tissues are classified based on their origin and development.
Primary meristems are derived from the promeristem and are responsible for the primary growth of the plant.
Intrafascicular cambium is a type of primary meristem located within the vascular bundles of stems and roots.
Cork cambium (phellogen) and interfascicular cambium are examples of secondary meristems,as they arise from permanent tissues during secondary growth.

(A) The $Apical$ $Cell$ $Theory$ was proposed by $Carl$ $Wilhelm$ $von$ $Nageli$ in $1858$. This theory states that the entire plant body is derived from a single apical cell. It is applicable to lower plants like algae, bryophytes, and pteridophytes, but it does not explain the shoot apex organization in higher plants like gymnosperms and angiosperms, where a group of cells is responsible for growth. Therefore, the correct option is $A$.

(D) Lateral meristems are meristems that are found in the mature regions of roots and shoots of many plants,particularly those that produce woody axis and appear later than primary meristems.
They are cylindrical meristems.
Examples of lateral meristems include:
$1$. Fascicular vascular cambium
$2$. Interfascicular cambium
$3$. Cork cambium (phellogen)
Since all the given options are examples of lateral meristems,the correct answer is $D$.

(A) In the process of secondary growth in dicot stems,the cork cambium or $Phellogen$ is a meristematic tissue.
$Phellogen$ cuts off cells on both sides.
The cells cut off on the outer side form the cork or $Phellem$.
The cells cut off on the inner side form the secondary cortex or $Phelloderm$.
$Bark$ is a non-technical term that refers to all tissues exterior to the vascular cambium,including secondary phloem,$Phelloderm$,$Phellogen$,and $Phellem$.

(A) Lateral meristems are responsible for secondary growth in plants, leading to an increase in girth.
Examples of lateral meristems include $Fascicular vascular cambium$, $Interfascicular cambium$, and $Cork cambium$ $(Phellogen)$.
$Intercalary meristem$ is a type of primary meristem found between mature tissues, primarily responsible for the elongation of internodes in grasses and other monocots.
Therefore, $Intercalary meristem$ is not a lateral meristem.

(A) The histogen theory,proposed by Hanstein,states that the root and shoot apices of plants are composed of distinct layers of meristematic cells called histogens. These histogens are responsible for the development of different tissue systems in the plant body. Specifically,histogens are the components of the apical meristem,which is located at the tips of roots and shoots.

(C) Meristematic tissue is a specialized plant tissue consisting of undifferentiated cells that possess the ability to divide continuously. These cells are actively involved in the formation of new cells,which contributes to both the primary and secondary growth of the plant. Therefore,the correct option is $C$.

(C) Primary tissues are derived from the apical meristems and are responsible for the primary growth of the plant.
In a woody dicot tree,secondary growth occurs in the stems and roots,leading to the formation of secondary tissues (secondary xylem and phloem).
However,the shoot tips and root tips (apical meristems) continue to produce primary tissues throughout the life of the plant to facilitate elongation.
Therefore,the shoot tips and root tips are the regions that primarily contain primary tissues.

(C) According to the Histogen theory proposed by Hanstein,the apical meristem of the root is divided into three distinct zones:
$1$. $Dermatogen$: It gives rise to the epidermis.
$2$. $Periblem$: It gives rise to the cortex.
$3$. $Plerome$: It gives rise to the central stele,which includes the pith,pericycle,and vascular tissues.
Therefore,the pith is formed by the $Plerome$.

(D) Wound cambium is a type of meristematic tissue that develops at the site of an injury in plants.
It is considered a $Secondary$ $meristem$ because it arises from differentiated cells that regain the ability to divide.
It is also known as $Induced$ $cambium$ because its formation is triggered by external injury.
Since it is located on the sides of the stem or root and contributes to secondary growth (callus formation),it is classified as a $Lateral$ $meristem$.
Therefore,all the given options are correct.

(C) The continuous growth of plants throughout their life is due to the presence of meristematic tissues at specific locations.
Meristematic tissues consist of actively dividing cells that undergo mitosis to produce new cells.
These new cells then differentiate into various permanent tissues,contributing to the increase in length and girth of the plant.
Therefore,meristematic tissue is responsible for the continuous growth of plants.

(A) Meristematic tissue is responsible for the continuous growth in plants.
These tissues consist of actively dividing cells that are capable of mitosis.
They are located in specific regions of the plant body,such as the root and shoot tips (apical meristems),which allow the plant to increase in length and girth throughout its life.

(B) : Lateral meristems are the meristems present along the lateral sides of stems and roots. They divide in the radial direction,leading to secondary growth. The vascular cambium (formed by intrafascicular and interfascicular cambium) and the cork cambium (phellogen) are examples of lateral meristems. These tissues are responsible for the increase in the girth (diameter) of stems and roots.

(D) The correct answer is $(d)$.
Meristems are classified based on their position in the plant body into apical,intercalary,and lateral meristems.
Lateral meristems are responsible for secondary growth and are located on the lateral sides of the stem and root. Examples include vascular cambium (which consists of intrafascicular and interfascicular cambium) and cork cambium (phellogen).
Intercalary meristems are located between permanent tissues and are responsible for the elongation of internodes in grasses and other monocots. Therefore,intercalary meristem is not a lateral meristem.

(D) $Dermatogen$ is the outermost layer of the apical meristem that gives rise to the epidermis.
$Periblem$ is the middle layer of the apical meristem that develops into the cortex.
$Plerome$ is the central core of the apical meristem that gives rise to the stele,which includes the vascular tissues (xylem and phloem).
Therefore,vascular tissues develop from the $plerome$ region.

(B) The correct answer is $B$.
An internode is the portion of a plant stem located between two adjacent nodes.
Intercalary meristems are located at the internodes and are typically found in the stems of grasses and other monocotyledonous plants,such as sugarcane.
In the early stages of development,the internode is entirely or partially meristematic.
As the plant grows,some parts of the internode mature more rapidly than others.
This differential growth rate,driven by the activity of the intercalary meristem,results in the variable lengths of internodes observed in the culm of sugarcane.

(B) The given figure illustrates the growth regions in a plant body.
$A$ is located at the top of the shoot axis,representing the Shoot apical meristem,which is responsible for the growth of the stem and leaves.
$B$ is located at the tip of the root,representing the Root apical meristem,which is responsible for the downward growth of the root system.
Therefore,the correct identification is $A-$ Shoot apical meristem and $B-$ Root apical meristem.

(D) The cells in the root and shoot apex regions are meristematic cells. These cells are characterized by:
$1$. Being rich in protoplasm.
$2$. Having large and conspicuous nuclei.
$3$. Possessing primary cell walls that are thin and cellulosic,which allows for rapid cell division and expansion.
$4$. Having abundant plasmodesmatal connections to facilitate communication between adjacent cells.
Therefore,all the given statements are correct.

(C) The root apex is divided into three zones: the zone of cell division (meristematic zone),the zone of elongation,and the zone of maturation.
$1$. The meristematic zone consists of cells that are small,thin-walled,and rich in protoplasm with large,conspicuous nuclei.
$2$. These cells divide repeatedly to produce new cells for the plant body.
$3$. Therefore,the description provided corresponds to the meristematic region.

(D) The cells in the root apex and shoot apex are meristematic cells.
These cells are characterized by:
$1$. Constant division (meristematic activity).
$2$. Thin,primary cell walls rich in cellulose.
$3$. Large,conspicuous nuclei.
$4$. Dense cytoplasm.
$5$. Small or absent vacuoles (they do not show increased vacuolation,which is a feature of mature cells).
Therefore,the correct characteristics are $a$ (constantly dividing),$b$ (primary cell walls),and $e$ (large conspicuous nuclei).
Thus,the correct option is $a, b, e$.

(C) The root tip is divided into three zones: the region of meristematic activity,the region of elongation,and the region of maturation.
$1$. The region of meristematic activity is located a few millimeters above the root cap.
$2$. The cells in this region are very small,thin-walled,and possess a dense protoplasm (cytoplasm).
$3$. These cells divide repeatedly to produce new cells.
$4$. The region of elongation is characterized by cells that undergo rapid elongation and enlargement.
$5$. The region of maturation is where cells differentiate and mature,often producing root hairs.
Therefore,the characteristic feature of the meristematic region is having dense cytoplasm.

(D) Lateral meristems are meristems that occur in the mature regions of roots and shoots of many plants,particularly those that produce woody axis and appear later than primary meristems.
They are cylindrical meristems.
Examples of lateral meristems include:
$1$. Fascicular vascular cambium (found within vascular bundles).
$2$. Interfascicular cambium (formed from medullary rays).
$3$. Cork cambium (phellogen).
Since all the given options represent types of lateral meristems,the correct answer is $D$.

(D) Statement $(1)$ is correct: Apical meristems are found at the tips of roots and shoots.
Statement $(2)$ is incorrect: Apical meristems are primary meristems,not secondary.
Statement $(3)$ is incorrect: Intercalary meristems are primary meristems that occur between mature tissues,not in the mature region itself,and they do not appear later than primary meristem.
Statement $(4)$ is correct: Fascicular vascular cambium,interfascicular cambium,and cork cambium are examples of lateral meristems,which are secondary meristems.
Therefore,statements $(1)$ and $(4)$ are correct.

(D) In the provided diagram of a shoot apex,the labels represent different structures:
$X$ represents the shoot apical meristem.
$Z$ represents the leaf primordium.
$Y$ represents the differentiated vascular tissue (or developing leaf/stem tissue below the meristematic region).
Therefore,$Y$ corresponds to the differentiated vascular tissue.

(A) During the formation of leaves and elongation of the stem,some cells 'left behind' from the shoot apical meristem constitute the axillary bud.
These buds are present in the axils of leaves and are capable of forming a branch or a flower.
Therefore,the axillary bud originates from the apical meristem.