Internal structure of stem Questions in English

(B) The stele is the central part of the root or stem containing the tissues derived from the procambium.
$A$ $Protostele$ is the simplest and most primitive type of stele,characterized by a solid central core of $Xylem$ surrounded by a layer of $Phloem$,$Pericycle$,and $Endodermis$.
Unlike other types of steles,it lacks a central $Pith$ (parenchymatous tissue) in the middle of the $Xylem$ core.
Therefore,the correct answer is $B$.

(B) In monocot stems,the vascular bundles are conjoint,collateral,and closed. These bundles are scattered throughout the ground tissue,a specific arrangement known as an $Atactostele$.

(A) Intraxyllary phloem is also known as internal phloem.
It originates from the procambium and is a type of primary phloem that occurs on the inner side of the primary xylem.
It is considered a primary anomalous structure.
Examples include members of the families $Apocynaceae$ and $Solanaceae$.

(B) Phloem parenchyma is a component of the phloem tissue in angiosperms.
It is generally present in most dicotyledonous plants.
However, it is characteristically absent in most monocotyledonous plants, such as maize $(Zea mays)$.
Therefore, phloem parenchyma is absent in the maize stem.

(C) . Companion cells are characteristic features of angiosperms only. In gymnosperms like $Pinus$,companion cells are absent and are replaced by albuminous cells (also known as Strasburger cells) which perform similar functions.

(B) The correct answer is $B$.
In a bicollateral vascular bundle,the phloem is present on both the outer and inner sides of the xylem,with two strips of cambium located between the xylem and the two phloem layers.
This type of vascular bundle is a characteristic feature of the family $Cucurbitaceae$,which includes plants like $Cucurbita$ and $Lagenaria$.

(C) $eustele$ is a type of siphonostele in which the vascular tissue in the stem forms a ring of discrete vascular bundles around a central pith.
This arrangement is a characteristic feature of the stems of $dicotyledonous$ plants (dicots).
In dicots, the vascular bundles are arranged in a ring, which is a defining feature of the $eustele$ type of stele organization.

(D) The centrifugal arrangement of xylem is known as $Endarch$.
In this condition,the $Protoxylem$ is situated towards the center (pith) of the axis,and the $Metaxylem$ develops towards the periphery.
This type of arrangement is a characteristic feature of the stems of flowering plants.

(C) In dicot stems,the vascular bundles are arranged in a ring around the pith. This type of stele,where the vascular bundles are arranged in a ring with distinct interfascicular regions,is known as a eustele.
Protostele,siphonostele,and actinostele are types of steles typically found in Pteridophytes.

(B) The cortex is a region of ground tissue located between the epidermis and the vascular cylinder (stele) in stems and roots.
Its primary functions include the storage of food (in the form of starch) and water.
Additionally,in many dicotyledonous plants,the cells of the cortex (specifically the pericycle or outer cortical layers) can dedifferentiate to form the cork cambium (phellogen),which is responsible for secondary growth (extra-stelar cambium).
Therefore,the correct answer is $B$.

(C) The hypodermis is a layer of cells located just below the epidermis. In many plants,especially in herbaceous climbers,the hypodermis consists of collenchyma cells. These cells provide mechanical support and tensile strength to the plant stem,allowing it to climb and withstand mechanical stress.

(D) In plant anatomy, the pith (or medulla) consists of parenchyma cells located in the center of the stem or root.
In a $Dicot$ stem, the central region is occupied by a well-developed pith composed of parenchyma cells.
In a $Monocot$ root, the central region is also occupied by a large, well-developed pith.
Conversely, in a $Dicot$ root, the pith is either absent or very small, and in a $Monocot$ stem, the vascular bundles are scattered, and there is no distinct pith.
Therefore, a well-developed pith is characteristic of the $Dicot$ stem and $Monocot$ root.

(D) In monocot stems,the vascular bundles are numerous and scattered throughout the ground tissue.
Each vascular bundle is typically surrounded by a sclerenchymatous bundle sheath.
In contrast,dicot stems have vascular bundles arranged in a ring.
Bryophytes do not possess true vascular tissues (xylem and phloem).
Dicot roots have a radial arrangement of vascular bundles.
Therefore,the correct answer is $D$ (Monocot stem).

(B) The hypodermis is the layer situated just below the epidermis. In dicot stems,the hypodermis is composed of collenchyma cells,which provide mechanical support and flexibility. In contrast,in monocot stems,the hypodermis is composed of sclerenchyma cells,which provide rigid mechanical support to the plant.

(B) The endodermis of a dicot stem contains abundant starch grains, which is why it is commonly referred to as the $starch \ sheath$.

(D) In a completely mature vascular bundle of a monocot stem,the protoxylem elements disintegrate to form a cavity known as the lysigenous water cavity or protoxylem lacuna. These cavities are filled with water and help in the conduction of water.

(D) Medullary rays (also known as pith rays) are radial strips of parenchyma cells that extend between the vascular bundles in the stem.
In a $Dicot$ stem,the vascular bundles are arranged in a ring.
The parenchyma cells present between these vascular bundles are known as medullary rays,which facilitate the radial conduction of water and food.
Therefore,medullary rays are a characteristic feature of the $Dicot$ stem.

(B) In monocot stems,the vascular bundles are scattered and each vascular bundle is surrounded by a prominent sheath of sclerenchymatous fibres,known as the bundle sheath. In contrast,dicot stems have vascular bundles arranged in a ring,and monocot roots do not possess this specific sclerenchymatous bundle sheath.

(A) In a dicot stem,the hypodermis is composed of collenchyma cells,which provide mechanical strength to the young stem.
In contrast,the hypodermis in a monocot stem is typically composed of sclerenchyma cells.
Therefore,the presence of a collenchymatous hypodermis is a diagnostic feature of a dicot stem.

(C) The vascular bundles in a dicot stem are described as follows:
$1$. Conjoint: $A$ vascular bundle containing both xylem and phloem together is called conjoint.
$2$. Collateral: $A$ vascular bundle in which the phloem is situated towards the outer side and the xylem towards the inner side is called collateral.
$3$. Open: When a strip of cambium is present between the xylem and phloem,the vascular bundle is referred to as open. This allows for secondary growth.
Therefore,the vascular bundles in a dicot stem are conjoint,collateral,and open.

(B) In a $Monocot$ stem,the vascular bundles are scattered throughout the ground tissue. There is no clear demarcation between the cortex,endodermis,pericycle,and pith. The ground tissue consists of a mass of parenchyma cells that surrounds the vascular bundles,making it impossible to distinguish the cortex and pith separately.

(A) In the $T.S.$ of the stem of $Cucurbita$ (family $Cucurbitaceae$),the vascular bundles are bicollateral.
Bicollateral vascular bundles are characterized by the presence of phloem on both the outer and inner sides of the xylem.
In contrast,the sunflower stem $(Helianthus)$ possesses conjoint,collateral,and open vascular bundles,where phloem is present only on the outer side of the xylem.
Therefore,the presence of bicollateral vascular bundles is the diagnostic feature used to distinguish $Cucurbita$ stem from sunflower stem.

(B) In plant anatomy,the pith (medulla) consists of parenchyma cells located in the center of the stem or root.
$1$. In $Monocot$ roots,the pith is large and well-developed,occupying the central region.
$2$. In $Dicot$ stems,the pith is also well-developed and occupies the central portion of the stem,surrounded by vascular bundles.
Therefore,abundant pith is a characteristic feature of $Monocot$ roots and $Dicot$ stems.

(A) In a collateral vascular bundle,the phloem is situated towards the outer side (periphery) and the xylem is situated towards the inner side (center).
In monocot stems,the vascular bundles are typically collateral and closed (lacking cambium).

(D) In $Monocot$ stem,each vascular bundle is surrounded by a sheath of $Sclerenchymatous$ fibers,known as the bundle sheath.
This sheath is extensively developed at the upper and lower faces of the vascular bundles.
Therefore,the correct option is $D$.

(D) In a monocot stem,the ground tissue consists of a mass of parenchyma cells with no clear distinction into cortex,endodermis,pericycle,and pith.
Therefore,the endodermis and the cortex are not differentiated as distinct layers in the monocot stem.
Since both endodermis and cortex are absent as distinct layers,option $(d)$ is the correct answer.

(A) In plants,vascular bundles are classified based on the arrangement of xylem and phloem.
$1$. Conjoint vascular bundles are those where xylem and phloem are present on the same radius.
$2$. Collateral bundles have phloem on the outer side and xylem on the inner side.
$3$. Closed vascular bundles are those that lack cambium between xylem and phloem,preventing secondary growth.
These characteristics are typical of monocot stems. In contrast,dicot stems possess open vascular bundles due to the presence of cambium.

(B) In monocot stems,the vascular bundles are described as $closed$ because they lack the $cambium$ layer between the $xylem$ and $phloem$.
Since $cambium$ is responsible for the formation of secondary $xylem$ and secondary $phloem$ (secondary growth),its absence prevents secondary growth from occurring in monocot stems.

(A) The vascular bundles in $Cucurbita$ are bicollateral and open.
In a bicollateral vascular bundle,the phloem is present on both the outer and inner sides of the xylem.
There are two strips of cambium present: one between the outer phloem and xylem,and another between the inner phloem and xylem.
Therefore,there are two cambial strands in the vascular bundle of $Cucurbita$.

(C) Sap wood is the peripheral part of the secondary xylem that is physiologically active and contains living cells,stored food materials,and high water content. Due to the presence of these nutrients and moisture,it is highly susceptible to microbial attack and decay when exposed freely. In contrast,heart wood is the central,non-functional part of the secondary xylem,which is filled with tannins,resins,oils,and gums,making it resistant to decay.

(B) In a typical dicotyledonous stem,the vascular bundles are arranged in a ring around the pith.
This arrangement is a characteristic feature of dicot stems,which distinguishes them from monocot stems where vascular bundles are scattered throughout the ground tissue.
Each vascular bundle in a dicot stem is conjoint,collateral,and open (possessing cambium between xylem and phloem).

(C) Phloem parenchyma is a component of the phloem tissue in angiosperms.
It is generally present in dicot stems,dicot leaves,and dicot roots.
However,phloem parenchyma is characteristically absent in the phloem of most monocotyledons,including the monocot stem.
Therefore,the correct answer is monocot stem.

(B) Bordered pits are characteristic features of the xylem vessels found in angiosperms (both monocots and dicots).
In gymnosperms,xylem vessels are generally absent,and water conduction occurs through tracheids which possess bordered pits.
However,among the given options,the presence of xylem vessels with bordered pits is a defining characteristic of angiosperms.
Since both monocots and dicots are angiosperms,and the question asks for the group where they are found,the most appropriate answer in the context of typical plant anatomy questions is dicots,as they show more prominent vessel development.

(A) The presence of numerous scattered vascular bundles and the absence of cambium are characteristic features of monocotyledonous stems.
In monocot stems,vascular bundles are closed (lack cambium),which means they do not undergo secondary growth.
Among the given options,$A$ (Sugarcane and Grass) are monocotyledonous plants,whereas the others (Sunflower,Neem,Radish,Pea,Peepal) are dicotyledonous plants that possess open vascular bundles with cambium.

(B) In the stem of $Cucurbita$ (a member of the family $Cucurbitaceae$),the vascular bundles are bicollateral.
Bicollateral vascular bundles are those in which the phloem is present on both the outer and inner sides of the xylem,with two strips of cambium present between the xylem and the two phloem layers.

(D) In the vascular bundles of monocot stems like $Maize$ ($Zea$ $mays$),the protoxylem elements disintegrate to form a water-containing cavity known as the lysigenous cavity or protoxylem lacuna. This is a characteristic feature of monocot stems.

(C) The characteristics described are:
$1$. Conjoint: Xylem and phloem are present in the same bundle.
$2$. Collateral: Phloem is located on the outer side and xylem on the inner side.
$3$. Endarch: Protoxylem is towards the center (pith) and metaxylem is towards the periphery.
$4$. Scattered: Vascular bundles are distributed throughout the ground tissue.
These features are diagnostic of a $Monocot$ stem. In $Dicot$ stems, vascular bundles are arranged in a ring.

(C) Barley $(Hordeum \text{ } vulgare)$ is a monocotyledonous plant.
In monocot stems, the vascular bundles are scattered throughout the ground tissue.
Each vascular bundle is surrounded by a sclerenchymatous bundle sheath.
The vascular bundles are 'closed' because they lack cambium, meaning they do not show secondary growth.
Therefore, the vascular bundles in a barley stem are closed and scattered.

(A) In a $Monocot$ stem,the vascular bundles are scattered throughout the ground tissue. The ground tissue is not differentiated into cortex,endodermis,pericycle,and pith. Instead,it consists of a uniform mass of parenchyma cells. In contrast,dicot stems,dicot roots,and monocot roots show a clear differentiation of tissues into cortex and pith (or central stele).

(D) The 'girdling experiment' involves removing a ring of bark (phloem) from the stem to demonstrate that food is transported through the phloem. In dicot stems,vascular bundles are arranged in a ring,making it easy to remove the phloem without affecting the xylem. However,in monocot plants,vascular bundles are scattered throughout the ground tissue. Because the phloem is not arranged in a distinct outer ring,it is impossible to remove the phloem without damaging the xylem and other tissues. Therefore,the experiment cannot be performed successfully in monocots.

(A) In dicot stems,the vascular bundles are arranged in a ring. These bundles are conjoint (xylem and phloem are present on the same radius),collateral (phloem is on the outer side and xylem on the inner side),and open (cambium is present between xylem and phloem). This type of stele,where vascular bundles are arranged in a ring,is known as a eustele. Therefore,conjoint collateral vascular bundles and eustele are characteristic features of the dicot stem.

(C) In monocot stems,the vascular bundles are numerous and scattered throughout the ground tissue. This specific type of stele arrangement is known as an $Atactostele$.
$Eustele$ is characterized by vascular bundles arranged in a ring.
$Dictyostele$ is a siphonostele that is dissected into separate vascular bundles.
$Solenostele$ is a type of siphonostele with a single gap.

(C) In a monocot stem,the vascular bundles are scattered in the ground tissue. Each vascular bundle is conjoint,collateral,and closed. $A$ characteristic feature of monocot stems (like maize) is the presence of a lysigenous water cavity (protoxylem lacuna) formed by the disintegration of protoxylem elements. Furthermore,the xylem vessels are arranged in a $Y$-shaped pattern within the vascular bundle.

(C) In a monocot stem,the vascular bundles are scattered throughout the ground tissue.
Each vascular bundle is 'closed',meaning it lacks a cambium between the xylem and phloem,which prevents secondary growth.
Furthermore,each vascular bundle is typically surrounded by a bundle sheath made of sclerenchymatous cells,which provides mechanical support to the stem.

(C) The polycyclic condition refers to the presence of multiple rings of vascular bundles in the stem. This is a characteristic feature of certain monocot stems,such as those found in the family $Dracaena$ or $Yucca$,where secondary growth occurs in a unique manner,leading to the formation of multiple vascular rings.

(A) In monocotyledonous stems,such as the $Maize$ stem,the vascular bundles are numerous and scattered throughout the ground tissue.
Each vascular bundle is surrounded by a sclerenchymatous bundle sheath.
In contrast,dicotyledonous stems like the $Sunflower$ stem have vascular bundles arranged in a ring.
Roots and leaves have different anatomical arrangements,making $Maize$ stem the correct answer.

(C) In monocot stems like maize $(Zea \ mays)$,the hypodermis is composed of sclerenchymatous cells.
These cells provide mechanical strength and support to the stem.
In contrast,dicot stems typically possess a collenchymatous hypodermis.

(A) The hypodermis is the layer of cells located just below the epidermis.
In dicot stems,the hypodermis consists of collenchyma cells,which provide mechanical strength to the young stem.
In contrast,monocot stems typically have a sclerenchymatous hypodermis.
Therefore,the collenchymatous hypodermis is a characteristic feature of dicot stems.

(D) In monocot stems,the vascular bundles are conjoint,collateral,and closed.
'Conjoint' means xylem and phloem are present in the same bundle.
'Collateral' means phloem is on the outer side and xylem is on the inner side.
'Closed' means there is no cambium present between xylem and phloem,so they do not show secondary growth.
'Endarch' means protoxylem is towards the center (pith) and metaxylem is towards the periphery.

(A) Hydrophytes are plants that grow in water or in very wet environments.
Since water is abundantly available,these plants do not require extensive vascular tissues for water transport.
Furthermore,because the surrounding water provides buoyancy,they do not require significant mechanical tissue for support.
Additionally,since they are submerged or floating in water,they do not need a thick cuticle to prevent water loss,leading to a reduction in these structures.