The tissue system Questions in English

(D) The outer protective tissues in plants are the epidermis and the epiblema (also known as piliferous layer or rhizodermis in roots).
Epidermis is the outermost layer of the primary plant body in stems and leaves,providing protection against mechanical injury and water loss.
Epiblema is the outermost layer of the root,which is responsible for the absorption of water and minerals from the soil.

(D) The Histogen theory,proposed by Hanstein,states that the root apex is composed of three distinct histogens:
$1$. Dermatogen: Gives rise to the epidermis.
$2$. Periblem: Gives rise to the cortex.
$3$. Plerome: Gives rise to the central stele (vascular cylinder),which includes the xylem and phloem.
Therefore,the plerome is responsible for the differentiation of the stele.

(A) During the development of a vascular bundle,the procambium cells differentiate first.
Following this,the primary phloem is formed towards the periphery,and subsequently,the primary xylem is formed towards the center.
This sequence of differentiation ensures the proper arrangement of vascular tissues within the plant body.

(C) In a $Bicollateral$ vascular bundle,the phloem is present on both the outer and inner sides of the xylem.
This type of vascular bundle is commonly found in the family $Cucurbitaceae$ (e.g.,pumpkin,cucumber).
In contrast,a $Collateral$ bundle has phloem only on the outer side,a $Radial$ bundle has xylem and phloem in alternate radii,and an $Amphicribral$ (or $Hadrocentric$) bundle has xylem surrounded by phloem.

(A) concentric vascular bundle is a type of vascular bundle where one tissue completely surrounds the other.
There are two types of concentric vascular bundles:
$1$. Amphicribral (Hadrocentric): The xylem is in the center and is completely surrounded by phloem.
$2$. Amphivasal (Leptocentric): The phloem is in the center and is completely surrounded by xylem.
Option $A$ describes the amphicribral condition,which is a classic definition of a concentric vascular bundle.

(B) In plants, vascular bundles are classified based on the arrangement of xylem and phloem.
$1$. When xylem and phloem are situated on the same radius, the vascular bundle is known as a $Conjoint$ vascular bundle.
$2$. In $Radial$ bundles, xylem and phloem are arranged in an alternate manner on different radii.
$3$. In $Concentric$ bundles, one vascular tissue surrounds the other.
$4$. $Exarch$ refers to the condition where protoxylem lies towards the periphery, which is a characteristic of roots.
Therefore, the correct answer is $Conjoint$.

(A) Vascular bundles are classified based on the presence or absence of cambium between xylem and phloem.
$1$. Open vascular bundles: These contain cambium between the xylem and phloem,which allows for secondary growth. These are characteristic of dicotyledonous stems.
$2$. Closed vascular bundles: These lack cambium between the xylem and phloem,meaning they do not undergo secondary growth. These are characteristic of monocotyledonous stems.
Therefore,vascular bundles containing cambium are called open vascular bundles.

(A) The cortex is the ground tissue located between the epidermis and the stele in stems and roots.
In most plants,the cortical cells are parenchyma cells that primarily function in the storage of food materials like starch.
While some cortical cells in specific plants (like aquatic plants or young stems) may contain chloroplasts,the most fundamental characteristic of mature cortical cells is that they are generally non-photosynthetic and lack chlorophyll.
Therefore,the most appropriate answer is chlorophyll.

(C) The hypodermis is a layer of cells located immediately below the epidermis in stems and leaves. Its primary function is to provide mechanical support to the plant organ,helping it withstand environmental stresses such as wind. In dicot stems,it is typically composed of collenchyma,which provides both flexibility and tensile strength.

(D) Laticifers are specialized cells or vessels that contain latex,a milky,viscous fluid.
They are commonly found in plants belonging to families like $Euphorbiaceae$,$Apocynaceae$,and $Moraceae$.
$Hevea$ (rubber tree),$Calotropis$ (milkweed),and $Euphorbia$ are all well-known examples of plants that possess laticiferous tissues.
Therefore,the correct answer is all of the above.

(A) vascular bundle in which the phloem is situated on both the outer and inner sides of the xylem,separated by strips of cambium,is known as a $Bicollateral$ $open$ vascular bundle.
In this arrangement,there are two cambium strips: one between the outer phloem and xylem,and another between the inner phloem and xylem.
This type of vascular bundle is characteristic of the family $Cucurbitaceae$.

(B) The ground tissue system in plants consists of all tissues except the epidermis and vascular bundles. It includes simple tissues such as parenchyma,collenchyma,and sclerenchyma. In primary stems and roots,ground tissue consists of the cortex,pericycle,pith,and medullary rays. In leaves,the ground tissue consists of a thin-walled chloroplast-containing cell called mesophyll.

(C) Lenticels are lens-shaped openings found in the bark of woody plants.
These structures allow for the exchange of gases between the internal tissues of the stem and the outer atmosphere.
The tissue filling the lenticel consists of loosely arranged,thin-walled,living parenchymatous cells,which are known as complementary cells.

(B) Lenticels are lens-shaped openings found in the bark of woody stems and roots that allow for gas exchange between the internal tissues and the external atmosphere.
These openings are filled with loosely arranged,thin-walled,non-suberized parenchyma cells known as complementary cells.
Because these cells are loosely arranged with large intercellular spaces and lack suberin,they facilitate the diffusion of gases like $O_2$ and $CO_2$.

(C) The concept of tissue systems in plants was introduced by the German botanist Julius von Sachs in $1875$. He classified plant tissues into $3$ distinct systems based on their location and function:
$1$. Epidermal tissue system (dermal system)
$2$. Ground tissue system (fundamental system)
$3$. Vascular tissue system (conducting system)
Therefore,the correct answer is Sachs.

(D) Xylem consists of four types of elements: $1.$ Tracheids,$2.$ Vessels,$3.$ Xylem fibers,and $4.$ Xylem parenchyma.
Among these,tracheids,vessels,and xylem fibers are dead tissues at maturity because they lack protoplasm.
Xylem parenchyma is the only living component of the xylem tissue,as it contains a nucleus and cytoplasm,and is responsible for the storage of food materials like starch or fat and the radial conduction of water.

(C) Suberin is a complex,hydrophobic,and waxy substance found in the cell walls of cork cells,endodermis,and exodermis of plants. Chemically,it is a polymer composed of long-chain fatty acids (such as phellonic acid) and phenolic compounds. Among the given options,it is most closely associated with fatty acid derivatives.

(B) In plants,vascular bundles are classified based on the presence or absence of cambium.
$1$. If cambium is present between the xylem and phloem,it allows for secondary growth,and such vascular bundles are called 'Open' vascular bundles.
$2$. If cambium is absent,they are called 'Closed' vascular bundles.
$3$. Since the intrafascicular cambium is a type of cambium found within the vascular bundle,its presence makes the bundle 'Open'.

(A) In a concentric vascular bundle,one vascular tissue (either xylem or phloem) completely surrounds the other.
When the phloem surrounds the xylem,it is known as an amphicribral or hadrocentric vascular bundle.
This type of arrangement is a specific form of a concentric vascular bundle.
Therefore,the correct option is $A$.

(C) Amphicribral or hadrocentric vascular bundles are those in which the xylem is located in the center and is completely surrounded by phloem.
In these bundles,the xylem is typically mesarch,meaning the protoxylem is situated in the center and the metaxylem develops towards the periphery.
Therefore,the correct type of vascular bundle in this context is mesarch.

(B) The outer surface of the aerial parts of plants,such as leaves and stems,is covered by a waxy,non-cellular layer known as the $Cuticle$.
This layer is primarily composed of $Cutin$,a fatty acid derivative,and wax.
The main function of the $Cuticle$ is to prevent excessive water loss through transpiration and to protect the plant from mechanical injury and pathogens.

(B) The aerial parts of plants,such as leaves and stems,are covered by a thin,waxy,and water-repellent layer known as the cuticle.
This cuticle is primarily composed of cutin,a fatty acid derivative,and is often coated with epicuticular waxes.
These waxes help in reducing water loss through transpiration and provide protection against environmental stress,pathogens,and mechanical injury.
Therefore,the correct answer is $B$ (Wax).

(D) The epidermis of plant leaves and stems is covered with pores called $stomata$.
Each $stomata$ is surrounded by a pair of specialised epidermal cells known as $guard$ $cells$.
In many cases,these $guard$ $cells$ are further surrounded by another category of less modified epidermal cells known as $subsidiary$ $cells$ (or accessory cells),which provide structural and functional support to the $guard$ $cells$.

(B) : Ground tissue can be defined as all the tissues except epidermis and vascular bundles. Ground tissue constitutes the interior of organs except the vascular system. It consists of simple tissues such as parenchyma,collenchyma,and sclerenchyma. Parenchymatous cells are usually present in the cortex,pericycle,pith,and medullary rays in the primary stems and roots. The ground tissue system of the leaves is called mesophyll.

(B) : In dicot stems,cambium is present between xylem and phloem,and such vascular bundles are called open. In monocot stems,the cambium is absent,and such vascular bundles are called closed. Cambium consists of meristematic cells which are capable of producing secondary xylem and secondary phloem.

(C) Vessels are specialized conducting elements found in the xylem tissue of angiosperms.
Their primary function is the long-distance transport of water and dissolved mineral salts from the roots to the aerial parts of the plant.
Unlike phloem,which transports food,or parenchyma,which stores food,vessels are dead,hollow,tube-like structures that provide a low-resistance pathway for the upward movement of water (xylem sap).

(D) Trichomes are epidermal outgrowths on the stem or other parts of the plant.
They are generally multicellular,though they can be unicellular in some cases.
They can be branched or unbranched,and they can be soft or stiff.
Therefore,all the given options are correct descriptions of trichomes.

(C) $Vessels$ are long,cylindrical,tube-like structures made up of many cells called vessel members,each with lignified walls and a large central cavity.
They are devoid of protoplasm at maturity.
$Vessels$ are characteristic features of $angiosperms$ and are primarily responsible for the conduction of water and minerals.
$Companion$ $cells$ are specialized $parenchymatous$ cells associated with $sieve$ $tube$ $elements$ in the $phloem$,not with $vessels$ in the $xylem$.
Therefore,the statement that $vessels$ are attached with $companion$ $cells$ is incorrect.

(D) The epidermal tissue system in plants consists of the epidermis,epidermal appendages (such as trichomes and root hairs),and stomata.
$1$. The epidermis is the outermost layer of the primary plant body.
$2$. Stomata are structures present in the epidermis of leaves that regulate gas exchange.
$3$. Trichomes are epidermal hairs on the stem.
$4$. Root hairs are unicellular elongations of the epidermal cells of the root.
$5$. The pericycle is a layer of cells located between the endodermis and the vascular bundles,which is part of the ground tissue system,not the epidermal tissue system.

(A) The epidermis is the outermost layer of the primary plant body. In many plants,especially those in dry environments,the epidermis is covered by a thick,waxy,thick layer called the cuticle. The primary function of this waxy cuticle is to prevent the loss of water through evaporation (transpiration). Therefore,it acts as a protective barrier against desiccation.

(C) In plants,vascular bundles are classified based on the presence or absence of cambium.
Open vascular bundles contain cambium between the xylem and phloem,which allows for secondary growth.
Closed vascular bundles lack cambium between the xylem and phloem,meaning they do not undergo secondary growth.
Therefore,closed vascular bundles lack cambium.

(B) The $Sieve$ $tube$ $cell$ of vascular plants (angiosperms) is a specialized cell involved in the transport of food (phloem).
At maturity,these cells lose their nucleus and many other organelles to facilitate the efficient flow of sap through the sieve plates.
In contrast,nerve cells,Amoeba,and typical animal cells possess a well-defined nucleus.

(C) Sieve tubes are the main conducting elements of phloem in angiosperms.
They are long,tube-like structures arranged longitudinally and are associated with companion cells.
Their end walls are perforated in a sieve-like manner to form 'sieve plates'.
Mature sieve tube elements possess a peripheral layer of cytoplasm and a large central vacuole,but they lack a nucleus.
The presence of peripheral cytoplasm and perforated end walls (sieve plates) facilitates the efficient translocation of food materials.

(A) bicollateral vascular bundle is a type of conjoint vascular bundle where the phloem is present on both the outer and inner sides of the xylem.
This means the xylem is sandwiched between two layers of phloem.
This arrangement is commonly found in the stems of plants belonging to the family $Cucurbitaceae$.

(D) During the development of vascular bundles in plants,the procambium is the meristematic tissue that gives rise to the vascular tissues.
As the procambium differentiates,it gives rise to the primary vascular tissues.
Specifically,the procambium differentiates into primary phloem and primary xylem.
In most vascular bundles,the primary phloem develops first (protophloem),followed by the development of primary xylem (protoxylem).

(C) Lenticels are small,lens-shaped openings found in the bark of woody stems and roots.
Their primary function is to facilitate the exchange of gases between the internal tissues of the plant and the external atmosphere.
While some transpiration may occur through them,their main physiological role is gaseous exchange.

(A) In plants,the ground tissue system consists of all tissues except the epidermis and vascular bundles. It includes simple tissues such as parenchyma,collenchyma,and sclerenchyma. In primary stems and roots,ground tissue consists of the cortex,pericycle,pith,and medullary rays. In leaves,it consists of thin-walled chloroplast-containing cells called mesophyll.

(C) Vascular bundles are classified into two types based on the presence or absence of cambium:
$1$. Open vascular bundles: These contain cambium between the xylem and phloem,allowing for secondary growth. These are typically found in dicot stems.
$2$. Closed vascular bundles: These lack cambium between the xylem and phloem,meaning they do not undergo secondary growth. These are typically found in monocot stems.
Therefore,in closed vascular bundles,the cambium is absent.

(B) The primary conducting elements of $Xylem$ are $Vessels$ and $Tracheids$.
$Tracheids$ are elongated,narrow cells with tapered ends,whereas $Vessels$ are cylindrical,tube-like structures.
The fundamental difference between these two elements lies in the nature of the perforations at their end walls.
$Vessels$ possess large perforations (perforation plates) at their end walls,which allow them to form a continuous pipe-like structure for efficient water transport.
In contrast,$Tracheids$ lack such large perforations and are connected to each other primarily through $Pits$.

(A) The stomatal apparatus consists of the stomatal aperture,guard cells,and the surrounding specialized epidermal cells known as subsidiary cells. These cells provide structural and functional support to the guard cells during the opening and closing of the stomata.

(B) In many monocot leaves,such as grasses,certain adaxial epidermal cells along the veins modify themselves into large,empty,colourless cells called $bulliform$ cells.
When these cells absorb water and are turgid,the leaf surface is exposed.
However,during very dry weather,these $bulliform$ cells lose water due to stress and become flaccid.
This loss of turgidity causes the leaves to curl inwards to minimize the surface area exposed to the atmosphere,thereby reducing the rate of transpiration and preventing water loss.

(N/A) The three basic tissue systems in flowering plants are as follows:

Tissue System	Tissues Included
$1$. Epidermal tissue system	Epidermis,trichomes,hairs,and stomata
$2$. Ground tissue system	Parenchyma,collenchyma,sclerenchyma,and mesophyll
$3$. Vascular tissue system	Xylem,phloem,and cambium

(N/A) $\rightarrow$ On the basis of their structure and location,there are three types of tissue systems: Epidermal tissue system,ground or fundamental tissue system,and vascular or conducting tissue system.
$\rightarrow$ Epidermal Tissue System: The epidermal tissue system forms the outermost covering of the whole plant body and comprises epidermal cells,stomata,and epidermal appendages (trichomes and hairs).
$\rightarrow$ The epidermis is the outermost layer of the primary plant body. It is made up of elongated,compactly arranged cells which form a continuous layer.
$\rightarrow$ Epidermis is usually single-layered. Epidermal cells are parenchymatous with a small amount of cytoplasm lining the cell wall and a large vacuole.
$\rightarrow$ The outside of the epidermis is often covered with a waxy thick layer called the cuticle,which prevents the loss of water.
$\rightarrow$ Cuticle is absent in roots.
$\rightarrow$ Stomata are structures present in the epidermis of leaves. Stomata regulate the process of transpiration and gaseous exchange.
$\rightarrow$ In dicot plants,each stoma is composed of two bean-shaped cells known as guard cells.
$\rightarrow$ In grasses,the guard cells are dumb-bell shaped. The outer walls of guard cells (away from the stomatal pore) are thin and the inner walls (towards the stomatal pore) are highly thickened.
$\rightarrow$ The guard cells possess chloroplasts and regulate the opening and closing of stomata.
$\rightarrow$ Sometimes,a few epidermal cells in the vicinity of the guard cells become specialized in their shape and size and are known as subsidiary cells.
$\rightarrow$ The stomatal aperture,guard cells,and the surrounding subsidiary cells are together called the stomatal apparatus.
$\rightarrow$ The cells of the epidermis bear a number of hairs. The root hairs are unicellular elongations of the epidermal cells and help absorb water and minerals from the soil.

(N/A) $\rightarrow$ All tissues except the epidermis and vascular bundles constitute the ground tissue system.
$\rightarrow$ The ground tissue system consists of simple tissues such as parenchyma,collenchyma,and sclerenchyma.
$\rightarrow$ Parenchymatous cells are usually present in the cortex,pericycle,pith,and medullary rays in primary stems and roots.
$\rightarrow$ In leaves,the ground tissue consists of thin-walled,chloroplast-containing cells and is called mesophyll.

(N/A) $\rightarrow$ The vascular system consists of complex tissues, the phloem and the xylem. The xylem and phloem together constitute vascular bundles.
$\rightarrow$ In dicotyledonous stems, cambium is present between phloem and xylem. Such vascular bundles, because of the presence of cambium, possess the ability to form secondary xylem and phloem tissues, and hence are called open vascular bundles.
$\rightarrow$ In the monocotyledons, the vascular bundles have no cambium present in them. Hence, since they do not form secondary tissues, they are referred to as closed vascular bundles.
$\rightarrow$ When xylem and phloem within a vascular bundle are arranged in an alternate manner on different radii, the arrangement is called radial, such as in roots.
$\rightarrow$ In the conjoint type of vascular bundles, the xylem and phloem are situated at the same radius of vascular bundles.
$\rightarrow$ Such vascular bundles are common in stems and leaves.
$\rightarrow$ The conjoint vascular bundles usually have the phloem located only on the outer side of xylem.

(N/A) $(i)$ Location: Found in the endodermal cells of dicot roots,where suberin and lignin thicken the radial and tangential walls in the form of a strip.
$\Rightarrow$ Function: Acts as a barrier that is impermeable to water,forcing water to move through the symplastic pathway.
$(ii)$ Location: Found in the endodermis of dicot stems (e.g.,sunflower),where the cells contain abundant starch grains.
$\Rightarrow$ Function: Serves as a storage site for starch,hence it is often referred to as the starch sheath.

(N/A) $(i)$ Resin duct:
Location: Found in the cortex of gymnosperm stems (e.g.,Pinus).
Function: Secretes resin,which provides mechanical strength and protection against pathogens.
$(ii)$ Passage cells:
Location: Thin-walled cells present in the endodermis of roots,opposite to protoxylem.
Function: Facilitate the radial transport of water and dissolved minerals from the cortex to the stele.
$(iii)$ Albumin cells:
Location: Present in the phloem of gymnosperms.
Function: Associated with sieve cells; they perform metabolic functions similar to companion cells in angiosperms.

(N/A) $ \Rightarrow $ Modification of epidermal cells: The following modifications are observed in epidermal tissues:
$(1)$ Root hairs:
$ \Rightarrow $ Structure: In the root hair region, epidermal cells of the root are extended as unicellular root hairs.
$ \Rightarrow $ Function: They increase the surface area for the absorption of water and mineral elements from the soil.
$(2)$ Trichomes:
$ \Rightarrow $ Structure: These are epidermal outgrowths on the stem. They can be unicellular or multicellular, branched or unbranched, and sometimes secretory.
$ \Rightarrow $ Function: They help in preventing water loss due to transpiration and protect the plant against herbivores.

(N/A)

Lenticels	Stomata
$\Rightarrow$ Lenticels are formed due to the loosening of cortical tissue.	$\Rightarrow$ Stomata are specific structures located in the epidermis.
$\Rightarrow$ They are mainly seen in the stem.	$\Rightarrow$ They are mainly seen on the lower surface of leaves.
$\Rightarrow$ Lenticels do not have guard cells.	$\Rightarrow$ Stomata have guard cells.
$\Rightarrow$ These pores are not regulated; they work for the removal of waste material.	$\Rightarrow$ The opening and closing of stomata are regulated; they are associated with gaseous exchange and the removal of extra water and waste material.

(A) The primary distinction between open and closed vascular bundles lies in the presence or absence of the cambium layer between the xylem and phloem.
$1$. Open Vascular Bundles: These contain a layer of cambium between the xylem and phloem. This cambium allows for secondary growth,which is characteristic of dicot stems.
$2$. Closed Vascular Bundles: These lack a cambium layer between the xylem and phloem. Consequently,they do not undergo secondary growth,which is characteristic of monocot stems.