Permanent Tissue Questions in English

(D) Based on the structural characteristics shown in the figures:
$1$. Figure $A$ shows cells with thin primary walls and intercellular spaces,which are characteristic of Parenchyma.
$2$. Figure $B$ shows cells with thickened corners (primary wall thickening),which is characteristic of Collenchyma.
$3$. Figure $C$ shows cells with very thick secondary walls and narrow lumens,which is characteristic of Sclerenchyma.
Therefore,the correct identification is $A$ - Parenchyma,$B$ - Collenchyma,$C$ - Sclerenchyma.

(D) Sclerenchyma fibres are a type of simple permanent tissue characterized by the following features:
$1$. They have thick,lignified cell walls which provide structural support.
$2$. They are typically elongated in shape.
$3$. They have pointed ends (tapering ends).
Since all these characteristics describe sclerenchyma fibres,the correct option is $D$.

(A) Collenchyma is a specialized supporting simple permanent tissue consisting of living cells.
These cells contain protoplasm and are characterized by unevenly distributed thickenings of cellulose,pectin,and hemicellulose on their cell walls.

(D) Sclerenchyma is classified into two types based on variation in form,structure,origin,and development: Fibres and Sclereids.
$1$. Fibres are thick-walled,elongated,and pointed cells.
$2$. Sclereids are generally spherical,oval,or cylindrical cells.
Therefore,both $(a)$ and $(b)$ are correct.

(A) Lignification refers to the deposition of lignin in the cell walls,which provides structural support and rigidity to the plant.
In vascular plants,the xylem tissue is characterized by the presence of lignified cell walls,particularly in tracheids,vessels,and xylem fibers.
This lignification makes the xylem cells dead at maturity and enables them to conduct water efficiently while providing mechanical strength.

(A) $P$-proteins (phloem proteins) are specialized proteins found in the phloem tissue of flowering plants. They are primarily associated with sieve tube elements. Their main function is to seal the sieve pores in response to injury,thereby preventing the loss of phloem sap.

(D) Tracheids are elongated or tube-like cells with thick and lignified walls and tapering ends. These are dead and lack protoplasm. The inner layers of the cell walls have thickenings which vary in form. In flowering plants,both tracheids and vessels are the main water-transporting elements.

(C) Sclerenchyma cells are thick-walled,lignified,and dead at maturity.
These cells provide mechanical support to the $Pinus$ needle,helping it maintain its structure against environmental stress.
Sclerenchyma may be fibrous or sclereid in nature.

(A) Parenchyma is the most primitive type of permanent tissue.
In hydrophytes (aquatic plants),parenchyma develops abundant air spaces and is known as aerenchyma.
Aerenchyma helps in floatation by providing buoyancy to the plants in water.

(C) Complex tissues are made up of more than one type of cells which work together as a unit.
$Xylem$ and $Phloem$ are the main complex tissues in plants,which are collectively known as conducting tissues.
$Collenchyma$ is a simple permanent tissue.
$Apical$ $meristem$ is a type of meristematic tissue.
$Idioblast$ is a specialized parenchyma cell containing non-living inclusions.

(B) Companion cells are thin-walled,elongated cells that are connected to sieve tube elements via plasmodesmata within the phloem.
They are a characteristic feature of angiosperms and play a crucial role in regulating the metabolic activities of sieve tube elements through their own nucleus.
In contrast,pteridophytes and gymnosperms (other vascular plants) lack companion cells and instead possess specialized cells known as albuminous cells.

(D) The fibres associated with the phloem,pericycle,and cortex are referred to as stem,bast,or soft fibres.
These fibres are primarily derived from dicotyledonous plants.
Therefore,phloem fibres are commonly known as bast fibres.

(A) Anatomically, jute fibres are classified as bast fibres or phloem fibres.
These fibres are found in the pericycle of the stem.
Examples of plants yielding bast fibres include $Corchorus capsularis$ (jute), $Hibiscus cannabinus$ (patsan), and $Crotalaria juncea$ (sunnhemp).
These fibres are also referred to as extraxylary fibres because they are located outside the xylem tissue.

(B) In xylem,vessels $(I)$ and tracheids $(II)$ are dead cells at maturity because they lose their protoplasm to facilitate water conduction.
Companion cells $(III)$ are specialized parenchyma cells found in the phloem of angiosperms. They are living cells that contain a dense cytoplasm and a large nucleus,which helps regulate the metabolic activities of the adjacent sieve tube elements.

(A) Phloem fibres (bast fibres) are made up of sclerenchymatous cells.
These are generally absent in the primary phloem but are found in the secondary phloem.
These are much elongated,unbranched,and have pointed,needle-like apices.
The cell wall of phloem fibres is quite thick.
At maturity,these fibres lose their protoplasm and become dead.
Phloem fibres of jute,flax,and hemp are used commercially.

(B) The correct answer is Collenchyma.
Collenchyma occurs in layers below the epidermis in dicotyledonous plants. It is found either as a homogeneous layer or in patches.
It consists of cells which are thickened at the corners due to the deposition of cellulose,hemicellulose,and pectin.
Collenchymatous cells may be oval,spherical,or polygonal and often contain chloroplasts.
These cells assimilate food when they contain chloroplasts.
Intercellular spaces are absent in this tissue.
They provide mechanical support to the growing parts of the plant,such as young stems and the petiole of a leaf.

(D) The correct answer is All except $IV$.
Sclerenchyma is classified into two types based on variation in form,structure,origin,and development: fibres and sclereids.
$1.$ Fibres are thick-walled,elongated,and pointed cells that generally occur in groups in various parts of the plant.
$2.$ Sclereids are spherical,oval,or cylindrical,highly thickened dead cells with a very narrow cavity (lumen).
$3.$ Sclereids are commonly found in the fruit wall of nuts,the pulp of fruits like guava,pear,and sapota,the seed coats of legumes,and the leaves of tea.
$4.$ The micropyle is an opening in the ovule/seed,not a structure composed of sclereids.
Therefore,statements $I, II,$ and $III$ are correct,while $IV$ is incorrect.

(C) Complex tissues are permanent tissues that consist of more than one type of cell.
All these different types of cells work together as a single unit to perform a common function.
Xylem and phloem are the most common examples of complex permanent tissues in plants,which are primarily responsible for the conduction of water,minerals,and food.

(D) In mature angiosperms,the sieve tube elements are living cells that lack a nucleus at maturity. This allows them to conduct food materials more efficiently. Companion cells,which are associated with sieve tubes,retain their nuclei and regulate the metabolic activities of the sieve tube elements.

(C) Cells produced by both primary and secondary meristems undergo structural and functional differentiation.
During this process,they lose their ability to divide and become permanent or mature cells.

(C) Tracheids are elongated cells with tapered ends. Their cell walls are usually extensively thickened by the deposition of lignin,which provides structural support. Water flows from one tracheid to another through unthickened regions known as pits in the cell walls. They are the primary water-conducting elements in gymnosperms and pteridophytes,and are also present in angiosperms.

(A) Sieve tube elements are the main conducting cells of the phloem.
They are long,slender,tube-like structures arranged in longitudinal series.
They possess peripheral cytoplasm and a large central vacuole,but they lack a nucleus at maturity.
They contain $P$-proteins (phloem proteins) in their lumen.
The end walls are perforated to form sieve plates,which are lined with callose,not lignin.
Therefore,the statement that they become impregnated with lignin is incorrect,as lignin is a characteristic of xylem elements (tracheids and vessels).

(C) Parenchyma cells are the most common simple permanent tissue in plants.
These cells are living and possess thin cell walls made up of cellulose.
They are generally isodiametric in shape and perform functions like photosynthesis,storage,and secretion.

(A) Collenchyma differs from parenchyma in possessing thick cell walls due to the deposition of pectin at the corners.
- Sclerenchymatous cells lack protoplasm at maturity.
- Both parenchyma and collenchyma,when they contain chloroplasts,are known as Chlorenchyma.
- Both collenchyma and parenchyma are simple permanent tissues that have lost their capacity to divide; therefore,they are not meristematic.

(C) Collenchyma cells are characterized by the deposition of cellulose,hemicellulose,and pectin at the corners of the cells.
This deposition leads to the thickening of the cell walls at these points,which results in the absence of intercellular spaces between the collenchyma cells.
Therefore,intercellular spaces are absent in collenchyma.

(D) Sclerenchyma cells are typically elongated,narrow,and have thick,lignified cell walls with few or no protoplasts.
They are generally dead at maturity and provide mechanical support to the plant organs.
Specifically,sclerenchyma fibers are characterized by being elongated,thick-walled,and having tapering ends,which matches the description provided.

(B) Sclereids are a type of sclerenchyma cells that are highly thickened,dead,and provide mechanical support to plant organs. They are commonly found in the fruit walls of nuts,the pulp of fruits like guava,pear,and sapota,and in the seed coats of legumes.

(D) The correct statement is that a vessel is a long cylindrical tube-like structure made up of many cells called vessel members.
$A$. Angiosperms possess vessels in their xylem,so this is incorrect.
$B$. While vessels are characteristic of angiosperms,gymnosperms (like Gnetales) also possess them,making this statement less precise than $D$.
$C$. Vessel cells are dead at maturity because they lack protoplasm,so this is incorrect.
$D$. This is the accurate definition of a vessel.

(A) Xylem fibres are dead cells with highly thickened walls and narrow or obliterated central lumens. Due to the extreme deposition of lignin,the cell cavity (lumen) becomes very small or completely disappears,which is referred to as being obliterated.

(A) In most monocotyledons,phloem parenchyma is absent. Phloem parenchyma is composed of elongated,tapering cylindrical cells which have dense cytoplasm and nucleus. It is generally present in dicotyledons but is absent in most monocots.

(C) Collenchyma is a living mechanical tissue that provides both mechanical support and flexibility to the growing parts of plants. Unlike sclerenchyma,which is dead and rigid,collenchyma cells are flexible and possess the ability to grow and divide,allowing them to support organs like young stems and petioles without hindering their growth.

(A) Sclereids are classified based on their shape and size:
$1$. $Brachysclereids$: These are isodiametric (short and stone-like) sclereids,commonly found in the hard endocarp of fruits like coconut and the fleshy pulp of fruits like guava.
$2$. $Asterosclereids$: These are star-shaped sclereids.
$3$. $Osteosclereids$: These are bone-shaped or rod-shaped sclereids with swollen ends.
$4$. $Trichosclereids$: These are hair-like,elongated,and branched sclereids.
Therefore,the correct answer is $Brachysclereids$.

(C) Homoxylous plants are those that lack vessels in their xylem,such as most gymnosperms. In these plants,tracheids are the primary elements responsible for the conduction of water and minerals. Therefore,tracheids are the main water-conducting elements in homoxylous plants.

(B) The sieve tube elements and companion cells are connected by pit fields present between their common longitudinal walls. These pit fields facilitate the transport of materials between the two cells,as the sieve tube elements lack a nucleus at maturity and rely on the companion cells for metabolic support.

(B) During the end of the growing season,the sieve pores in old sieve tubes become blocked by the deposition of a polysaccharide called $Callose$.
This deposition of $Callose$ forms a $Callose$ pad or plug over the sieve plate,which effectively reduces or stops the transport of sugars and other organic solutes through the sieve tubes.

(A) Sclerenchyma cells are dead at maturity and possess extremely thick,lignified secondary cell walls.
The deposition of lignin provides mechanical strength and rigidity to the plant body.
Since the thickened secondary walls are primarily due to the deposition of lignin,the Reason correctly explains the Assertion.

(A) Sieve tubes and companion cells are ontogenetically related because they both originate from the same mother cell through a series of divisions.
Specifically,a single mother cell undergoes an unequal division to produce a smaller cell that differentiates into a companion cell and a larger cell that differentiates into a sieve tube element.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(B) In plants,the long-distance transport of organic and inorganic substances occurs through complex permanent tissues.
These complex permanent tissues are known as vascular tissues,which include $Xylem$ and $Phloem$.
$Xylem$ is responsible for the transport of water and minerals,while $Phloem$ is responsible for the transport of organic solutes (food).

(A) Tracheids are dead cells at maturity that form the primary water-conducting elements in gymnosperms and pteridophytes.
They possess a thick,lignified secondary cell wall,which provides high mechanical strength and elasticity.
This lignocellulosic secondary wall prevents the tracheids from collapsing under the extreme negative pressure (tension) generated during the transpiration pull.

(C) Fibres are a type of $Sclerenchyma$ tissue.
$Sclerenchyma$ cells are dead at maturity and possess thick,lignified secondary cell walls.
These cells provide mechanical strength and support to the plant body.
Fibres are elongated,narrow,and pointed cells that occur in bundles in various parts of the plant,such as the stem,leaves,and vascular tissues.

(B) The correct answer is $B$ (Hydrophytes).
$1$. Aerenchyma is a specialized type of parenchyma tissue that contains large air-filled spaces or lacunae.
$2$. These air spaces provide buoyancy to aquatic plants,allowing them to float on the water surface or remain upright in the water column.
$3$. Additionally,aerenchyma facilitates the exchange of gases,particularly oxygen,which is often limited in submerged aquatic environments.
$4$. Therefore,aerenchyma is a characteristic feature of hydrophytes (aquatic plants).

(N/A)

Tracheids	Vessels
$1$. They are unicellular elements primarily found in gymnosperms.	$1$. They are multicellular elements primarily found in angiosperms.
$2$. Their end walls are intact and possess pits for water conduction.	$2$. Their end walls are perforated or completely broken down to form a continuous tube.
$3$. Cells are narrow,elongated,and have tapering ends.	$3$. Cells are wide,cylindrical,and tube-like structures.
$4$. Water transport capacity is relatively lower.	$4$. Water transport capacity is significantly higher.

(A) The phloem parenchyma is composed of elongated,tapering cylindrical cells which have dense cytoplasm and nucleus.
Its primary functions include:
$1$. Storage of food materials such as starch,fats,and other substances like resins,latex,and mucilage.
$2$. It also assists in the radial conduction of food materials.

(N/A) The difference between softwood and hardwood is as follows:

Softwood	Hardwood
$(1)$ In gymnosperms, softwood mainly possesses tracheids.	$(1)$ In angiosperms, hardwood mainly consists of vessels.
$(2)$ It lacks vessels.	$(2)$ It lacks tracheids.

Softwood is typically produced by gymnosperms (conifers), which lack vessels in their xylem. Hardwood is typically produced by angiosperms (flowering plants), which possess vessels in their xylem.

(N/A)

Collenchyma	Sclerenchyma
$(1)$ It is found in the hypodermis of dicot stems.	$(1)$ It is found in the pericycle of stems and vascular bundles.
$(2)$ Cells are living and contain a nucleus.	$(2)$ Cells are dead at maturity.
$(3)$ Cell walls are thickened at the corners due to cellulose,hemicellulose,and pectin.	$(3)$ Cell walls are uniformly thickened with lignin.
$(4)$ Cells are oval,spherical,or polygonal in shape.	$(4)$ Cells are long,narrow,and fiber-like or sclereids.
$(5)$ It provides mechanical support and flexibility to growing parts.	$(5)$ It provides mechanical strength and rigidity to mature parts.

(N/A)

Parenchyma Tissue	Sclerenchyma Tissue
$(1)$ Cells are living and possess a thin cell wall made of cellulose.	$(1)$ Cells are generally dead at maturity and lack protoplasm.
$(2)$ Cell walls are thin and flexible.	$(2)$ Cell walls are highly thickened due to the deposition of lignin.
$(3)$ Intercellular spaces are usually present.	$(3)$ Intercellular spaces are absent.
$(4)$ Primary functions include photosynthesis,storage of food,and secretion.	$(4)$ Primary function is to provide mechanical strength and support to the plant organs.

(A) Parenchyma is the most common simple permanent tissue in plants.
It consists of relatively unspecialized cells with thin cell walls made of cellulose.
These cells perform various functions such as photosynthesis (when they contain chloroplasts,known as chlorenchyma),storage of food materials,and secretion of various substances.
Therefore,the correct answer is $A$.

(A) The image shows parenchyma cells,which are characterized by thin cell walls made of cellulose. Option $A$ states that the cell wall is thick,which is incorrect for parenchyma cells (collenchyma cells have unevenly thickened walls). Parenchyma cells are the primary components of the ground tissue system and perform various functions such as photosynthesis,storage,and secretion.

(B) The provided image shows cells with uneven thickening at the corners,which is a characteristic feature of collenchyma tissue.
Collenchyma cells are characterized by the deposition of cellulose,hemicellulose,and pectin at the corners of the cell wall.
Therefore,the thickening material present in this tissue is pectin.

(D) The structure shown in the image is a 'Sclereid',which is a type of Sclerenchyma.
Sclereids are commonly found in the pulp of guava,pear,and sapodilla,providing them with a gritty texture.
They are also found in the fruit walls of nuts,the leaves of tea,and the seed coats of legumes.
Therefore,the correct option is $D$.