Meristematic Tissue Questions in English

(A) Intercalary meristem is a type of meristematic tissue that is located between regions of mature tissues.
It is responsible for the growth in length of internodes,particularly in monocotyledonous plants like grasses.
These meristems are derived from the apical meristem but become separated from it by the development of permanent tissues as the plant grows.
Therefore,the correct option is $A$.

(C) The $Tunica-Corpus$ theory was proposed by $Schmidt$ in $1924$.
This theory explains the organization and development of the $Shoot$ $Apex$ in angiosperms.
According to this theory,the shoot apex consists of two distinct zones:
$1$. $Tunica$: The peripheral layer$(s)$ that divide anticlinally to increase the surface area.
$2$. $Corpus$: The central mass of cells that divide in various planes to increase the volume of the shoot apex.
Therefore,the correct option is $C$.

(A) The lateral meristem is responsible for secondary growth in plants,which leads to an increase in the diameter or girth of the stem and root. Examples include the vascular cambium and cork cambium. Apical meristems are responsible for primary growth (increase in length),while intercalary meristems are found at the base of leaves or internodes and help in elongation.

(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 is divided into two distinct zones based on the plane of cell division:
$1$. $Tunica$: The peripheral layer$(s)$ where cells divide primarily by anticlinal divisions,leading to surface growth.
$2$. $Corpus$: The central mass of cells where divisions occur in various planes,contributing to the increase in volume.
Therefore,the differentiation between $Tunica$ and $Corpus$ is determined by the plane of cell division.

(A) Monocot leaves,specifically the leaves of grasses,possess $Intercalary$ $meristem$.
This type of meristem is located between mature tissues and is responsible for the growth in length of the leaves and internodes.
It allows the plant to regenerate parts that have been removed by grazing animals.

(D) The procambium is a primary meristematic tissue derived from the apical meristem.
It differentiates into the primary vascular tissues,which include primary xylem and primary phloem.
Additionally,it gives rise to the vascular cambium,which is responsible for secondary growth in dicotyledonous plants.
Therefore,the procambium gives rise to primary vascular tissues and the vascular cambium.

(D) The development of a leaf primordium into a mature leaf involves specific meristematic activities.
Initially,the leaf primordium arises from the shoot apical meristem.
However,the subsequent growth and expansion of the leaf blade (lamina) are primarily driven by the activity of the marginal meristem,which is located along the edges of the developing leaf primordium.
Therefore,the correct sequence is that it starts with the apical meristem and is followed by the activity of the marginal meristem.

(C) The $Apical$ $\text{meristem}$ is responsible for the primary growth of plants. It is located at the tips of shoots and roots. During the formation of the shoot, some cells are left behind from the $Apical$ $\text{meristem}$ in the axils of leaves, which develop into $Axillary$ $\text{buds}$. The $Terminal$ $\text{bud}$ is the primary growing point at the apex of the stem, also derived from the $Apical$ $\text{meristem}$. Therefore, both axillary and terminal buds are products of the activity of the $Apical$ $\text{meristem}$.

(C) The quiescent center is a region found in the root apical meristem.
It consists of cells that have a very low rate of cell division.
These cells are characterized by having a thin cytoplasm and a small nucleus,which indicates their low metabolic activity compared to the surrounding actively dividing meristematic cells.
Therefore,option $C$ is the correct description.

(A) The root apical meristem is a region of actively dividing cells located at the tip of the root. It is responsible for the primary growth of the root system. Since all types of roots (taproots,fibrous roots,and adventitious roots) grow in length from their tips,the root apical meristem is present in all roots.

(D) In woody dicot plants,secondary growth occurs in the stems and roots,leading to the formation of secondary tissues. However,the apical meristems,which are responsible for primary growth,are located at the shoot tips and root tips. These regions continuously produce primary tissues throughout the life of the plant. Therefore,the shoot tips and root tips are the parts that contain primary tissues.

(B) According to the Histogen theory proposed by Hanstein,the shoot apex is divided into three distinct zones or histogens:
$1$. $Dermatogen$: 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 vascular tissue (xylem and phloem) and the pith.
Therefore,the vascular tissue originates from the $Plerome$.

(D) The growth in the length of the stem in monocots like sugarcane is primarily due to the activity of the $Intercalary$ $meristem$.
These meristems are located between mature 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 sugarcane is variable.

(B) Lawn grass is managed by regular mowing. When the top of the grass is cut,the apical bud (which is the source of apical dominance due to auxin production) is removed. This removal of apical dominance allows the intercalary meristems,which are located at the base of the nodes or internodes,to become active and stimulate the growth of the grass,leading to a thicker and more uniform lawn.

(A) The root apical meristem is responsible for the growth of the root.
It is located slightly behind the tip of the root, making it subterminal.
This is because the terminal end of the root is covered by a protective structure called the root cap $(root\,cap)$.
The root cap protects the delicate meristematic tissue as the root pushes through the soil.
Therefore, the presence of the root cap at the terminal end is the reason why the apical meristem is subterminal.
Both the Assertion and the Reason are correct, and the Reason is the correct explanation of the Assertion.

(C) The increase in the girth or diameter of a plant stem is known as secondary growth.
This growth is facilitated by lateral meristems,which include the vascular cambium and the cork cambium (phellogen).
While phellogen is a type of lateral meristem,the term 'lateral meristem' is the broader,more accurate category that encompasses all tissues responsible for secondary growth in thickness.
Therefore,lateral meristem is the primary tissue responsible for the increase in girth.

(A) The root apex and shoot apex are meristematic in nature.
These meristematic tissues are embryonic in origin.
They are primary in origin because they develop from embryonic tissues and primary in function because they form the primary structure of the plant,such as the root apex and shoot apex,which persist throughout the life of the plant.
Because these meristematic regions remain active throughout the plant's life,higher plants exhibit the feature of indefinite growth.
Therefore,the Reason correctly explains the Assertion.

(C) The regeneration of damaged grass after grazing is primarily due to the presence of $Intercalary$ $meristem$.
These meristems are located between mature tissues and are responsible for the growth in length of internodes in monocots,such as grasses.
When herbivores graze on grass,they remove the apical meristem,but the intercalary meristems allow the grass to continue growing from the base or nodes,facilitating rapid recovery.

(N/A) Meristems are specialized regions of plant growth where active cell division occurs. They are classified into three types based on their location:
$1$. Apical meristem: Located at the root and shoot apices. The shoot apical meristem is at the tip of the shoots,responsible for stem elongation and leaf formation. The root apical meristem aids in root elongation.
$2$. Intercalary meristem: Located between masses of mature tissues,specifically at the bases of leaves or internodes in grasses. It helps in the regeneration of parts removed by grazing herbivores. Both apical and intercalary meristems are considered primary meristems.
$3$. Lateral meristem: Found in the mature regions of roots and shoots. It is known as secondary meristem because it appears later in the plant's life. It is responsible for increasing the girth of the plant by adding secondary tissues. Examples include fascicular vascular cambium,interfascicular cambium,and cork cambium.

(N/A) $\rightarrow$ $A$ tissue is a group of cells having a common origin and usually performing a common function.
$\rightarrow$ Tissues are classified into two main groups based on whether the cells are capable of dividing or not: $(1)$ Meristematic tissue and $(2)$ Permanent tissue.

(N/A) $\rightarrow$ Growth in plants is largely restricted to specialized regions of active cell division called meristems.
$\rightarrow$ Plants have different kinds of meristems. They are as follows:
$(A)$ Apical Meristems: The meristems which occur at the tips of roots and shoots and produce primary tissues are called apical meristems.
$\rightarrow$ Root apical meristem occupies the tip of a root while the shoot apical meristem occupies the distant most region of the stem axis.
$\rightarrow$ During the formation of leaves and elongation of stem,some cells 'left behind' from shoot apical meristem constitute the axillary bud. Such buds are present in the axils of leaves and are capable of forming a branch or a flower.
$(B)$ Intercalary Meristem: The meristem which occurs between mature tissues is known as intercalary meristem. They occur in grasses and regenerate parts removed by the grazing herbivores.
Both apical meristems and intercalary meristems are primary meristems because they appear early in the life of a plant and contribute to the formation of the primary plant body.
$(C)$ Lateral Meristem: The meristem that occurs in the mature regions of roots and shoots of many plants,particularly those that produce woody axis and appear later than primary meristem,is called the secondary or lateral meristem.
$\rightarrow$ They are cylindrical meristems. Fascicular vascular cambium,interfascicular cambium,and cork cambium are examples of lateral meristems. These are responsible for producing the secondary tissues.

(N/A) Meristematic tissue is a group of actively dividing cells in plants that are responsible for growth.
Key characteristics include:
$1$. Cells are small,thin-walled,and have dense cytoplasm with a prominent nucleus.
$2$. They lack intercellular spaces.
$3$. They are capable of continuous cell division.
$4$. Based on their location,they are classified as apical,intercalary,and lateral meristems.
$5$. Apical meristems (as shown in the image for root and shoot apices) are responsible for primary growth in length.

(N/A) The apical meristematic tissue of the root and shoot can be studied by observing the growth patterns of onion roots.
$1$. Take two glass jars and fill them with water.
$2$. Place an onion bulb on each jar.
$3$. Observe the growth of roots in both bulbs for a few days.
$4$. Cut the root tips of one of the onions after a few days and observe the further growth.
$5$. It will be observed that the root whose tip was cut stops growing,demonstrating that the apical meristem is responsible for primary growth at the tips.

(N/A) Meristems consist of undifferentiated cells that possess the active capacity for continuous cell division,which is essential for rapid growth in tissue culture.
In contrast,permanent tissues consist of cells that have lost the capacity for division and have become specialized or differentiated to perform specific functions,making them less suitable for regeneration in culture.

(B) The rapid growth of lawn grass after mowing is primarily due to the presence of $Intercalary$ $meristem$.
These meristematic tissues are located at the base of the leaves or internodes in grasses.
When the apical part is removed by mowing,the $Intercalary$ $meristem$ becomes active and promotes the regeneration and rapid elongation of the grass blades.
This allows the grass to recover quickly from grazing or mowing.

(N/A) The meristematic cells near the root tip are characterized by:
- Rich protoplasm.
- Large,conspicuous nucleus.
- Thin,primary cellulosic cell walls.
- Fewer and smaller vacuoles.
- High metabolic activity with a greater number of mitochondria.
- Numerous plasmodesmata for intercellular communication.
$(b)$ The cells in the elongation zone of the root are characterized by:
- Increased vacuolation,which helps in cell enlargement.
- Significant increase in cell size and dimensions.
- Deposition of new cell wall materials to support the expanded cell structure.

(A) Meristematic cells are characterized by being rich in protoplasm and possessing large,conspicuous nuclei.
Their cell walls are primary in nature,thin,and cellulosic,with abundant plasmodesmatal connections.
In contrast,cells that are incapable of dividing (permanent cells) have attained their maximal size and show significant wall thickening and protoplasmic modifications,such as the presence of large vacuoles or the loss of active cytoplasm.

(B) Vascular cambium is the correct answer.
The meristematic layer responsible for the production (cutting off) of vascular tissues,specifically secondary xylem and secondary phloem,is known as the vascular cambium.
In a young stem,it exists as a single layer of cells located in patches between the primary xylem and primary phloem.
As the plant undergoes secondary growth,these patches join together to form a complete,continuous ring of meristematic tissue.

(D) Lateral meristems are meristematic tissues that are responsible for secondary growth in plants,leading to an increase in girth.
$A$. Intrafascicular cambium is a type of vascular cambium present within the vascular bundles,which is a lateral meristem.
$B$. Interfascicular cambium develops from medullary rays during secondary growth and is also a lateral meristem.
$C$. Phellogen,also known as cork cambium,is a lateral meristem responsible for the production of cork and secondary cortex.
$D$. Phelloderm is the secondary cortex formed by the phellogen on its inner side. It is a permanent tissue,not a meristematic one. Therefore,it is not a lateral meristem.

(C) The intercalary meristems are responsible for localized growth in plants.
They are essentially portions of the apical meristem that have been separated from the main apex during the development of the plant body.
These meristems are found at the base of leaves (as in the petiole),in the internodes of grasses,and at the base of nodes.
Therefore,the increase in the length of the petiole is primarily due to the activity of the intercalary meristem.

(A) The root apical meristem is responsible for the primary growth of the root and is located at the tip of the root.
Similarly,the shoot apical meristem is responsible for the primary growth of the shoot and is located at the distant most region of the stem axis.
Therefore,$A$ corresponds to the tip and $B$ corresponds to the stem.

(A) tissue is a group of cells performing a particular function. Tissues are mainly of two types:
$(i)$ Meristematic tissues: These tissues contain immature and young cells that are highly active and capable of continuous division and re-division. They include promeristem,primary meristem,secondary meristem,apical meristem,intercalary meristem,and lateral meristem.
$(ii)$ Permanent tissues: These are made up of mature cells that have lost the capacity to divide and have attained a permanent shape,size,and function,e.g.,simple (parenchyma,collenchyma,sclerenchyma) and complex (xylem,phloem) tissues.

(C) The meristem that lies between the regions of permanent tissues is called intercalary meristem.
Intercalary meristem is considered a part of the primary meristem because it originates from the apical meristem during the development of the plant body.
Since the primary meristem is responsible for the formation of the primary plant body,and intercalary meristem helps in the elongation of internodes,it is classified as a derivative of the primary meristem.

(D) Intercalary meristematic tissues are found between permanent tissues.
They are located at the base of internodes (e.g.,in grasses and bamboo),at the base of leaves (e.g.,in $Pinus$),or at the base of nodes (e.g.,in mint).
The activity of intercalary meristem is responsible for the elongation of the plant or its specific organs.

(C) The $Root$ $Apical$ $Meristem$ is located at the tip of the main root and its branches.
In the case of a tap root system,the root apical meristem is formed from the radicle part of the embryo or its derivatives.
In adventitious roots,the root apical meristem is produced from the derivatives of the shoot apex.

(D) Schmidt $(1924)$ proposed the tunica-corpus theory,which describes the presence of two distinct zones in the shoot apices of angiosperms.
The peripheral layer$(s)$ of cells is called the tunica,while the inner mass of cells is called the corpus,which is surrounded by the tunica.

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

(D) The meristematic tissue that is located at the growing tips of both roots and shoots is known as the apical meristem.
These cells are responsible for the primary growth of the plant,which leads to an increase in the length of the plant body.
Therefore,apical meristems are found at the tips of roots (root apical meristem) and the tips of shoots (shoot apical meristem).

(B) Intercalary meristem is present at the base of internodes,e.g.,in grasses $(Gramineae)$ or at the base of leaves,e.g.,in $Pinus$ or at the base of nodes,e.g.,mint.
Intercalary meristem is a part of the apical meristem that gets separated during the development of the plant body and is responsible for the increase in length of the plant axis,which is a characteristic of primary growth.

(D) The cambium present between the xylem and phloem of a vascular bundle is called the vascular cambium.
It is a lateral meristem that gives rise to secondary xylem and phloem and occurs in the form of a thin strip.
Vascular cambium present within the vascular bundle is specifically known as fascicular cambium.

(D) Meristematic activity is characterized by the presence of meristematic tissue,which is found at the root apex $(RAM)$ and shoot apex $(SAM)$.
These meristems are responsible for the formation of permanent tissues.
Axillary buds are formed from the cells left behind by the shoot apical meristem.
Since all the statements provided ($A$,$B$,and $C$) are scientifically correct,the correct choice is $D$.

(A) Apical meristems and intercalary meristems are classified as primary meristems because they appear early in the life of a plant.
They are responsible for the formation of the primary plant body,which includes the development of the stem,roots,and leaves.

(B) The provided diagram represents the longitudinal section of a shoot apex.
$A$ points to the leaf primordium,which is a young,developing leaf structure.
$B$ points to the axillary bud,which is a structure that develops in the axil of a leaf and has the potential to form a branch or flower.
$C$ points to the developing vascular tissue,which will differentiate into xylem and phloem.
Therefore,the correct identification is $A-$ Leaf primordium,$B-$ Axillary bud,$C-$ Vascular tissue.

(B) Meristematic tissue: These are groups of cells that are actively dividing and are responsible for the growth of the plant.
Permanent tissue: These are cells that have lost their ability to divide and have attained a specific shape,size,and function.

(B) During the formation of leaves and elongation of the stem,some cells 'left behind' from the shoot apical meristem remain in the axils of leaves. These cells constitute the axillary bud,which is capable of forming a branch or a flower.

(A) Lateral meristems are responsible for increasing the girth or diameter of the plant body.
Examples of lateral meristems include $Fascicular \text{ } vascular \text{ } cambium$, $Interfascicular \text{ } cambium$, and $Cork \text{ } cambium$.
$Intercalary \text{ } meristem$ is a type of primary meristem found in the internodal regions of grasses and is responsible for longitudinal growth, not lateral growth.

(B) Lateral meristem,which includes vascular cambium and cork cambium,is responsible for secondary growth in plants.
This process results in an increase in the diameter or girth of the plant axis (stems and roots).

(B) The intrafascicular cambium is present between the primary xylem and primary phloem within the vascular bundle. It is a type of meristematic tissue because its cells retain the ability to divide. It is primary in origin as it originates from the procambium during the development of the plant body.

(D) Meristematic cells are characterized by the following features:
$1$. They consist of actively dividing cells.
$2$. The cells are typically isodiametric with thin cellulosic cell walls.
$3$. They lack intercellular spaces between them.
$4$. They have very small or no vacuoles.
$5$. They lack reserve food materials and fully developed plastids (proplastids may be present).
Therefore,all the given options are correct characteristics of meristematic tissue.

(B) According to the histogen theory proposed by Hanstein,the shoot apex is divided into three distinct zones or histogens: Dermatogen,Periblem,and Plerome.
$1$. The Dermatogen is the outermost layer of the apical meristem.
$2$. It gives rise to the epidermis of the stem and leaves.
$3$. Therefore,the stem epidermis is derived from the Dermatogen.