Internal structure of root Questions in English

(B) Lateral roots are endogenous in origin,meaning they arise from tissues located inside the endodermis.
Specifically,they originate from the pericycle cells located opposite to the protoxylem points (or patches).
These pericycle cells undergo repeated divisions to form a root primordium,which eventually pushes through the endodermis and cortex to emerge as a lateral root.

(C) In angiosperms,the lateral roots are endogenous in origin.
They originate from the pericycle cells,which are located just inside the endodermis.
These cells undergo division to form the lateral root primordium,which then pushes through the cortex and epidermis to emerge.

(C) The Casparian strips are water-impermeable bands found in the endodermal cells of plant roots.
These strips are primarily composed of a waxy,hydrophobic substance called suberin.
In some cases,lignin may also be deposited along with suberin to provide additional structural support and impermeability.
Therefore,the correct composition is a mixture of lignin and suberin.

(A) In plants,the arrangement of xylem is classified based on the position of protoxylem relative to the metaxylem.
When the protoxylem is directed towards the periphery (outside) and the metaxylem is towards the center,the condition is known as $Exarch$.
This type of arrangement is characteristic of roots and is also referred to as $Centripetal \ xylem$ because the development of xylem proceeds towards the center.
Therefore,the correct option is $A$.

(A) In the roots of flowering plants,the xylem and phloem are arranged in an alternating manner on separate radii.
These vascular bundles are separated by parenchymatous cells.
This specific tissue located between the xylem and phloem bundles is known as the conjunctive tissue.

(C) According to the histogen theory proposed by Hanstein,the root apex is composed of three distinct layers of meristematic tissue called histogens.
These three histogens are:
$1$. Dermatogen: The outermost layer that gives rise to the epidermis (epiblema).
$2$. Periblem: The middle layer that develops into the cortex.
$3$. Pleurome: The central core that gives rise to the stele (vascular cylinder).
Therefore,there are $3$ histogens present at the apex of the root.

(B) The Korper-Kappe theory was proposed by Schüepp $(1917)$ to explain the organization of the root apical meristem.
In this theory,the term 'Korper' (German for 'body') refers to the central body of the root apex,while 'Kappe' (German for 'cap') refers to the root cap.
Therefore,the term Kappe is meant for the cap.

(B) The $Pericycle$ is a layer of cells located between the endodermis and the vascular bundles in roots. It consists of a single layer or multiple layers of thin-walled or thick-walled cells. It plays a crucial role in the initiation of lateral roots and secondary growth.

(B) In plants,the arrangement of xylem is classified based on the position of protoxylem and metaxylem relative to the center of the organ.
When the protoxylem is located towards the periphery and the metaxylem develops towards the center (centripetal development),the condition is called $Exarch$.
This type of arrangement is characteristic of the roots of flowering plants.
In contrast,$Endarch$ refers to the condition where protoxylem is towards the center and metaxylem is towards the periphery (centrifugal development),which is typical of stems.

(C) Passage cells are thin-walled cells found in the endodermis of roots,specifically located opposite to the protoxylem elements.
These cells allow the radial movement of water and dissolved minerals from the cortex into the xylem.
They are characteristic of monocot roots,where the endodermis remains thin-walled except for the Casparian strips,and these specific cells lack the suberin deposition.

(C) The endodermis is the innermost layer of the cortex in roots.
It is composed of a single layer of barrel-shaped cells that are closely packed without intercellular spaces.
These cells are characterized by the presence of Casparian strips,which are water-impermeable waxy material deposits (suberin) on their radial and tangential walls.
Therefore,the correct option is $C$.

(B) The correct answer is $B$.
The $Endodermis$ is the innermost layer of the cortex in roots.
It consists of a single layer of barrel-shaped,compactly arranged parenchymatous cells.
The radial and tangential walls of these cells contain water-impermeable,waxy material called $Suberin$,which forms the $Casparian$ strips.

(D) In roots,the xylem and phloem are arranged in an alternating manner on different radii.
Such vascular bundles are termed as radial vascular bundles.
This arrangement is a characteristic feature of root anatomy in plants.

(B) Passage cells are specialized thin-walled cells found in the endodermis of roots.
In the endodermis,most cells have $Casparian$ strips (thickened with suberin),which are impermeable to water.
However,the cells located opposite to the protoxylem elements remain thin-walled and lack $Casparian$ strips.
These cells are known as passage cells,and they facilitate the movement of water and dissolved minerals from the cortex into the vascular cylinder (stele).

(B) In a radial vascular bundle,the xylem and phloem are arranged in an alternate manner on different radii.
This type of vascular arrangement is a characteristic feature of roots in angiosperms,including both dicot and monocot roots.
In stems and leaves,the vascular bundles are typically conjoint (xylem and phloem are located on the same radius).
Therefore,the correct answer is $B$ (Dicot root).

(B) The Casparian strips are water-impermeable deposits of suberin found in the radial and tangential walls of the endodermal cells in roots.
These structures were first described and identified by the German botanist Robert Caspary in $1865$.
Therefore,the correct option is $B$.

(C) The endodermis is the innermost layer of the cortex in roots.
Its cells are characterized by the presence of Casparian bands,which are water-impermeable waxy deposits of suberin.
These bands prevent the apoplastic movement of water and solutes into the vascular cylinder,forcing them to enter the symplastic pathway.
Therefore,the presence of suberin lamellae and Casparian bands is the most significant diagnostic feature of endodermal cells.

(B) In plants,vascular bundles are classified based on the position of protoxylem and the number of xylem bundles.
$Exarch$ condition refers to the arrangement where protoxylem lies towards the periphery and metaxylem towards the center,which is a characteristic feature of roots.
$Polyarch$ condition refers to the presence of more than six xylem bundles.
Monocot roots typically exhibit a $polyarch$ arrangement (usually more than six xylem bundles) and $exarch$ xylem.
Therefore,$exarch$ and $polyarch$ vascular bundles are characteristic of monocot roots.

(B) In roots,the xylem arrangement is $Exarch$.
In an $Exarch$ condition,the $protoxylem$ is directed towards the periphery (outside) and the $metaxylem$ is directed towards the center of the organ.
This is a characteristic feature of the root anatomy in vascular plants.

(C) In dicot roots,the vascular bundles are radial,meaning the xylem and phloem are arranged in an alternating manner on different radii. They are separated by parenchymatous cells. This radial arrangement is a characteristic feature of roots,whereas conjoint vascular bundles (with cambium) are characteristic of stems.

(C) In a dicot root,the pith is either very small or completely absent. In contrast,a monocot root is characterized by the presence of a large,well-developed pith at the center of the vascular cylinder. Therefore,the presence of a well-developed pith is a distinguishing feature of monocot roots.

(B) The polyarch condition refers to the presence of many vascular bundles (typically more than $6$) in the root.
This condition is a characteristic feature of monocot roots.
In contrast,dicot roots typically show a diarch to hexarch condition (fewer vascular bundles).

(D) In dicotyledonous roots,the number of xylem and phloem bundles (vascular bundles) usually ranges from $2$ to $6$ (diarch to hexarch). $A$ high number of vascular bundles (polyarch,typically more than $6$) is a characteristic feature of monocotyledonous roots. Therefore,having $15-20$ vascular bundles is not a feature of dicot roots.

(A) In the monocot root,the cortex consists of several layers of thin-walled parenchyma cells with intercellular spaces.
These cells are responsible for the storage of food and water.
Therefore,the cortex is primarily composed of parenchymatous cells.

(C) In dicot roots,the vascular cambium develops during secondary growth,which leads to the formation of secondary xylem and secondary phloem.
Monocot roots do not undergo secondary growth because they lack a vascular cambium.
Therefore,the absence of cambium is a key anatomical difference between monocot and dicot roots.

(A) In $exarch$ xylem,the protoxylem is situated towards the periphery and the metaxylem is situated towards the center of the organ.
This arrangement is a characteristic feature of the roots of flowering plants.
In contrast,$endarch$ xylem,where the protoxylem is towards the center and metaxylem is towards the periphery,is a characteristic feature of stems.

(D) In a $Dicot$ root,the number of vascular bundles is usually limited,typically ranging from $2$ to $6$ (diarch to hexarch).
Specifically,a $Dicot$ root often exhibits $2$ to $5$ xylem bundles.
In contrast,$Monocot$ roots typically have more than $6$ xylem bundles,a condition known as polyarch.
$Monocot$ and $Dicot$ stems have vascular bundles arranged in a ring or scattered,which are conjoint and collateral,not categorized by the number of xylem bundles in the same way as roots.

(A) In a monocot root,a large and well-developed pith is present in the center. This pith is composed of loosely arranged parenchymatous cells that often contain abundant starch grains. Vascular cambium is absent in monocot roots,xylem is exarch (not endarch),and medullary rays are characteristic of stems,not roots.

(C) In dicot roots,the pericycle is composed of thin-walled parenchymatous cells. It is the site where lateral roots and vascular cambium originate during secondary growth.
In contrast,in the stems of many dicots,the pericycle is often present as semi-lunar patches of sclerenchymatous cells located above the phloem bundles.

(A) In roots,the xylem development is $exarch$,which means the protoxylem is directed towards the periphery and the metaxylem towards the center. This arrangement is known as $centripetal$ $xylem$ development,where the maturation of xylem proceeds from the periphery towards the center. In contrast,stems exhibit $endarch$ xylem development,where the protoxylem is directed towards the center and the metaxylem towards the periphery.

(B) In monocot roots,the vascular bundles are radial,meaning xylem and phloem are arranged in an alternating manner on different radii.
In roots,the xylem is exarch,which means the protoxylem lies towards the periphery and the metaxylem lies towards the center.
Therefore,monocot roots possess radial vascular bundles with exarch xylem.

(B) The $Casparian$ strips are characteristic features of the $Endodermis$ in roots.
These are water-impermeable,waxy bands made of $suberin$ that are deposited in the radial and tangential walls of the endodermal cells.
They prevent the apoplastic movement of water and solutes,forcing them to enter the vascular cylinder through the symplastic pathway.
Therefore,the correct option is $B$.

(A) Based on the anatomical structure of a dicot root $T.S.$:
$A$ points to the innermost layer of the cortex,which is the Endodermis.
$B$ points to the parenchymatous cells lying between the xylem and phloem,known as Conjunctive tissue.
$C$ points to the larger xylem vessels located towards the center,which are Metaxylem.
$D$ points to the smaller xylem vessels located towards the periphery,which are Protoxylem.
$E$ points to the vascular tissue responsible for food transport,the Phloem.
$F$ points to the central core,which is the Pith (often small or inconspicuous in dicot roots).
Therefore,the correct matching is $A =$ Endodermis,$B =$ Conjunctive tissue,$C =$ Metaxylem,$D =$ Protoxylem,$E =$ Phloem,$F =$ Pith.

(D) Monocot roots typically exhibit polyarch xylem conditions,meaning they have more than six xylem bundles,whereas dicot roots usually have two to four (diarch to tetrarch).
Monocot roots possess a large,well-developed central pith,which is either absent or very small in dicot roots.
Furthermore,monocot roots do not undergo secondary growth,whereas dicot roots exhibit secondary growth due to the activity of the vascular cambium.
Therefore,all the given statements correctly describe the differences between monocot and dicot roots.

(C) The anatomical structure of a typical monocot root,when viewed from the outer surface towards the center,consists of the following layers:
$1$. $Epiblema$ (or $Rhizodermis$): The outermost single layer of cells.
$2$. $Cortex$: $A$ multi-layered region of parenchyma cells located beneath the $Epiblema$.
$3$. $Endodermis$: The innermost layer of the cortex,characterized by the presence of Casparian strips.
$4$. $Pericycle$: The layer located just inside the $Endodermis$,which gives rise to lateral roots.
Therefore,the correct sequence is $Epiblema \rightarrow Cortex \rightarrow Endodermis \rightarrow Pericycle$.

(D) In plants,radial vascular bundles are a characteristic feature of roots.
In a dicot root,the number of vascular bundles (xylem and phloem patches) is typically $2$ to $4$.
When there are $4$ radial vascular bundles,the condition is known as tetrarch.
Monocot roots typically have more than $6$ vascular bundles,which is known as polyarch.
Stems possess conjoint vascular bundles,not radial ones.
Therefore,a structure with four radial vascular bundles is a dicot root.

(C) In the root apex of monocotyledons,the organization of the apical meristem is often described by the Korper-Kappe theory or specific initial groups.
According to the classical view of monocotyledon root apices,there are three distinct groups of initials:
$1$. The terminal group of initials gives rise to the root cap (calyptrogen).
$2$. The median group of initials gives rise to the dermatogen (epidermis) and the periblem (cortex).
$3$. The innermost group of initials gives rise to the plerome (stele/vascular cylinder).
Therefore,option $C$ is the correct description.

(A) In a dicot root,the xylem arrangement is described as exarch.
In an exarch condition,the protoxylem vessels are located towards the periphery (outer side) of the root,while the metaxylem vessels are located towards the centre (inner side).
This arrangement helps in the efficient transport of water from the root hairs towards the vascular cylinder.

(A) In dicotyledonous angiosperms,the root apical meristematic region differentiates into distinct zones. The dermatogen is the outermost layer of the root apical meristem,which originates from the terminal group of initials. This layer eventually gives rise to the epidermis and the epidermal tissue system of the root.

(A) The $Endodermis$ is the innermost layer of the cortex in roots.
It is characterized by the presence of $Casparian$ $strips$ on its radial and tangential walls.
These $Casparian$ $strips$ are composed of $suberin$, a water-impermeable, waxy substance.
This layer prevents the apoplastic movement of water into the vascular cylinder, forcing water to enter the symplastic pathway.

(C) In a $Dicot$ root,the pith is either absent or very small and inconspicuous.
In contrast,$Monocot$ roots have a large and well-developed pith.
$Monocot$ stems have scattered vascular bundles with no distinct pith,and $Dicot$ stems have a large,well-developed central pith.
Therefore,the correct answer is $Dicot$ root.

(B) The $Casparian$ strips are characteristic features of the $Endodermis$ in the roots of flowering plants.
These strips are composed of suberin,a water-impermeable waxy substance,which prevents the radial movement of water through the cell walls (apoplastic pathway).
Therefore,water must enter the cytoplasm of the endodermal cells to cross this barrier,allowing the plant to regulate the flow of water and solutes into the vascular cylinder.

(D) In the roots of flowering plants,the arrangement of xylem is $exarch$.
In an $exarch$ condition,the protoxylem is located towards the periphery (outer side) and the metaxylem is located towards the center (inner side) of the organ.
This is a characteristic feature of root anatomy,which helps in distinguishing it from stem anatomy where the arrangement is $endarch$.

(C) According to the Histogen theory proposed by Hanstein, the root apex consists of three distinct histogens:
$1$. $Dermatogen$: Forms the epidermis.
$2$. $Periblem$: Forms the cortex.
$3$. $Plerome$: Forms the stele (vascular cylinder).
In monocotyledonous plants, an additional fourth histogen called $Calyptrogen$ is present, which is responsible for the formation of the root cap $(root \, cap)$. Therefore, $Calyptrogen$ is the specific histogen found in the root apex of monocots.

(D) The endodermis is the innermost layer of the cortex in roots. In many monocot roots,the endodermal cells opposite to the protoxylem are thin-walled and lack the Casparian strips (suberin deposition). These specialized cells are known as passage cells. They facilitate the movement of water and dissolved solutes from the cortex into the vascular cylinder (stele). Therefore,passage cells are a characteristic feature of the endodermis in monocot roots.

(D) In dicot roots,the pericycle is responsible for the initiation of lateral roots.
During secondary growth,the cells of the pericycle located opposite to the protoxylem also participate in the formation of the vascular cambium ring.
Since the pericycle contributes to both lateral root formation and the development of the vascular cambium,the correct answer is $D$.

(B) In plants,the vascular arrangement in the root is $exarch$ (protoxylem towards the periphery),while in the stem,it is $endarch$ (protoxylem towards the center).
This transition from the $exarch$ condition of the root to the $endarch$ condition of the stem takes place in the region known as the $hypocotyl$ (the portion of the embryonic axis below the cotyledons).

(D) In plants,the arrangement of vascular bundles is classified based on the position of the protoxylem.
$1$. In roots,the protoxylem is directed towards the periphery,which is known as $exarch$ condition.
$2$. In stems,the protoxylem is directed towards the center,which is known as $endarch$ condition.
$3$. Monocot roots typically possess a large,well-developed pith in the center,whereas dicot roots have a small or absent pith.
$4$. Therefore,the combination of $exarch$ vascular bundles and a well-developed pith is a characteristic feature of $monocot$ roots.

(B) Passage cells are specialized thin-walled cells found in the endodermis of roots.
These cells are located opposite to the protoxylem elements.
They lack the Casparian strips (suberin deposits) that are present in other endodermal cells.
Therefore,they allow the radial movement of water and dissolved minerals from the cortex into the pericycle and subsequently into the vascular tissue.

(D) In a dicot root,the vascular bundles are typically radial and limited in number,usually ranging from $2$ to $6$ (diarch to hexarch).
$15-20$ vascular bundles (polyarch condition) are a characteristic feature of monocot roots,not dicot roots.
Radial vascular bundles,secondary growth,and a small or absent pith are all characteristic features of dicot roots.