Short Explanation:A tissue is a group of similar cells that work together to perform a particular function.In multicellular organisms, tissues create
division of labour.
In a unicellular organism such as Amoeba, a single cell performs all essential life processes.
In multicellular organisms such as plants and humans, millions of cells are present.
Different cells become specialised for different jobs.
Short Explanation:When meristematic cells stop dividing and become specialised
for specific functions, they form
permanent tissues.
The process by which cells become specialised in structure and function
is called differentiation.
Meristematic cells
Actively divide
Differentiated cells
Become specialised
Permanent tissue
Performs a specific function
π§ Reasoning Question:Why do permanent tissues generally stop dividing?
Answer:Their cells have differentiated and become specialised
for particular functions rather than continuous cell division.
π§ Reasoning Question:Are all permanent tissue cells dead?
Answer:No.Many permanent tissues contain living cells.
For example, parenchyma and collenchyma are living tissues.
Sclerenchyma cells are generally dead at maturity.
β Exam Alert:Do not write:“Permanent tissue means dead tissue.”That statement is incorrect.Permanent tissue means a tissue whose cells have
differentiated and generally lost the ability to divide.
6. Simple Permanent Tissues
Short Explanation:Simple permanent tissues are mainly made up of
one type of cell.The three important types are:Parenchyma, Collenchyma and Sclerenchyma.
πΏ Parenchyma
Storage and other basic functions.
Some forms perform photosynthesis.
π± Collenchyma
Provides support while allowing flexibility.
π³ Sclerenchyma
Provides strength and rigidity.
Feature
Parenchyma
Collenchyma
Sclerenchyma
Cells
Living
Living
Dead at maturity
Cell wall
Thin
Unevenly thickened
Very thick and lignified
Intercellular spaces
Usually present
Very little
Usually absent
Main role
Storage / photosynthesis
Support + flexibility
Strength + rigidity
πΏ Parenchyma
Parenchyma is a simple permanent tissue made up of living cells.
The cells generally have thin cell walls and may have intercellular spaces.
It commonly performs functions such as
storage.
When parenchyma contains chloroplasts, it can perform photosynthesis.
Such tissue is called chlorenchyma.
π§ Reasoning Question:Why is parenchyma suitable for storage?
Answer:Parenchyma cells are living and commonly have large vacuoles,
which can store substances such as food and water.
π§ Reasoning Question:A plant tissue contains parenchyma cells with chloroplasts.
What additional function can it perform?
Answer:It can perform photosynthesis because chloroplasts
contain chlorophyll.Such parenchyma is called chlorenchyma.
π Aerenchyma
In aquatic plants, parenchyma may contain large air spaces.
This specialised form is called aerenchyma.
π§ Reasoning Question:How can aerenchyma help an aquatic plant float?
Answer:The large air spaces provide buoyancy and help the plant remain
supported in water.
π± Collenchyma
Collenchyma consists of living cells whose walls are
unevenly thickened at the corners.
It provides mechanical support while allowing flexibility.
It is commonly found in young growing parts such as
leaf stalks and below the epidermis of stems.
π§ Reasoning Question:Why is collenchyma suitable for a young bending stem?
Answer:It provides mechanical support while retaining flexibility.
Therefore, the young stem can bend without easily breaking.
π§ Application Question:What would happen if a young plant part had only rigid tissue
and no flexible supporting tissue?
Answer:The plant part would be less flexible and could be more likely
to break when subjected to bending forces.
π³ Sclerenchyma
Sclerenchyma provides mechanical strength and rigidity.
Its cells generally have very thick walls containing
lignin and are dead at maturity.
Sclerenchymatous cells may occur in parts that need strong support,
such as fibres and the hard covering of some seeds and nuts.
π§ Reasoning Question:Why is sclerenchyma rigid?
Answer:Its cells have very thick, lignified walls.
Lignification makes the walls hard and provides mechanical strength.
π§ Reasoning Question:Why are sclerenchyma cells generally dead at maturity?
Answer:Their main role is mechanical strength.
The thick, lignified walls provide the required rigidity,
so the living contents are not essential when the cells mature.
Short Explanation:Complex permanent tissues contain
different types of cells
that work together to perform a common function.The two major complex tissues are:Xylem and Phloem.
π§ Xylem
Xylem conducts water and minerals from the roots towards
the aerial parts of the plant.
It also provides mechanical support.
The main components of xylem are:
tracheids, vessels, xylem parenchyma and xylem fibres.
π§ Reasoning Question:Why is xylem called a complex tissue?
Answer:Xylem contains different types of cells that work together
for conduction and support.
π Phloem
Phloem transports food, particularly sugars,
from regions where food is produced or available
to regions where it is required or stored.
The main components of phloem are:
sieve tubes, companion cells, phloem parenchyma and phloem fibres.
π§ Reasoning Question:Is phloem transport always downward?
Answer:No.Food is transported from a source to a sink.
Therefore, the direction depends on where food is produced
and where it is needed.
β Memory Rule:Xylem β Water + MineralsPhloem β Food
4. Types of Meristematic Tissue
Short Explanation:
Meristematic tissue is classified according to its position in the plant:
apical, intercalary and lateral meristem.
Type
Location
Main Function
Apical Meristem
Tips of roots and shoots
Increase in length
Intercalary Meristem
Base of leaves or internodes
Growth of particular regions
Lateral Meristem
Sides of stems and roots
Increase in girth/thickness
π§ Reasoning Question:A plant’s height increases rapidly. Which meristem is mainly responsible?
Answer:Apical meristem.It is present at the growing tips of roots and shoots and increases
the length of the plant.
π§ Reasoning Question:A stem becomes thicker as the plant grows older.
Which meristem is responsible?
Answer:Lateral meristem.It increases the girth or thickness of stems and roots.
π§ Reasoning Question:Why can grass regrow after being cut?
Answer:Intercalary meristematic regions can continue cell division
and produce new growth.
β Exam Memory Trick:
APICAL β A = Above / tip β LengthLATERAL β Side β GirthINTERCALARY β In-between regions β Growth
5. Permanent Tissue
Short Explanation:When meristematic cells stop dividing and become specialised
for specific functions, they form
permanent tissues.
The process by which cells become specialised in structure and function
is called differentiation.
Meristematic cells
Actively divide
Differentiated cells
Become specialised
Permanent tissue
Performs a specific function
π§ Reasoning Question:Why do permanent tissues generally stop dividing?
Answer:Their cells have differentiated and become specialised
for particular functions rather than continuous cell division.
π§ Reasoning Question:Are all permanent tissue cells dead?
Answer:No.Many permanent tissues contain living cells.
For example, parenchyma and collenchyma are living tissues.
Sclerenchyma cells are generally dead at maturity.
β Exam Alert:Do not write:“Permanent tissue means dead tissue.”That statement is incorrect.Permanent tissue means a tissue whose cells have
differentiated and generally lost the ability to divide.
6. Simple Permanent Tissues
Short Explanation:Simple permanent tissues are mainly made up of
one type of cell.The three important types are:Parenchyma, Collenchyma and Sclerenchyma.
πΏ Parenchyma
Storage and other basic functions.
Some forms perform photosynthesis.
π± Collenchyma
Provides support while allowing flexibility.
π³ Sclerenchyma
Provides strength and rigidity.
Feature
Parenchyma
Collenchyma
Sclerenchyma
Cells
Living
Living
Dead at maturity
Cell wall
Thin
Unevenly thickened
Very thick and lignified
Intercellular spaces
Usually present
Very little
Usually absent
Main role
Storage / photosynthesis
Support + flexibility
Strength + rigidity
πΏ Parenchyma
Parenchyma is a simple permanent tissue made up of living cells.
The cells generally have thin cell walls and may have intercellular spaces.
It commonly performs functions such as
storage.
When parenchyma contains chloroplasts, it can perform photosynthesis.
Such tissue is called chlorenchyma.
π§ Reasoning Question:Why is parenchyma suitable for storage?
Answer:Parenchyma cells are living and commonly have large vacuoles,
which can store substances such as food and water.
π§ Reasoning Question:A plant tissue contains parenchyma cells with chloroplasts.
What additional function can it perform?
Answer:It can perform photosynthesis because chloroplasts
contain chlorophyll.Such parenchyma is called chlorenchyma.
π Aerenchyma
In aquatic plants, parenchyma may contain large air spaces.
This specialised form is called aerenchyma.
π§ Reasoning Question:How can aerenchyma help an aquatic plant float?
Answer:The large air spaces provide buoyancy and help the plant remain
supported in water.
π± Collenchyma
Collenchyma consists of living cells whose walls are
unevenly thickened at the corners.
It provides mechanical support while allowing flexibility.
It is commonly found in young growing parts such as
leaf stalks and below the epidermis of stems.
π§ Reasoning Question:Why is collenchyma suitable for a young bending stem?
Answer:It provides mechanical support while retaining flexibility.
Therefore, the young stem can bend without easily breaking.
π§ Application Question:What would happen if a young plant part had only rigid tissue
and no flexible supporting tissue?
Answer:The plant part would be less flexible and could be more likely
to break when subjected to bending forces.
π³ Sclerenchyma
Sclerenchyma provides mechanical strength and rigidity.
Its cells generally have very thick walls containing
lignin and are dead at maturity.
Sclerenchymatous cells may occur in parts that need strong support,
such as fibres and the hard covering of some seeds and nuts.
π§ Reasoning Question:Why is sclerenchyma rigid?
Answer:Its cells have very thick, lignified walls.
Lignification makes the walls hard and provides mechanical strength.
π§ Reasoning Question:Why are sclerenchyma cells generally dead at maturity?
Answer:Their main role is mechanical strength.
The thick, lignified walls provide the required rigidity,
so the living contents are not essential when the cells mature.
Short Explanation:Complex permanent tissues contain
different types of cells
that work together to perform a common function.The two major complex tissues are:Xylem and Phloem.
π§ Xylem
Xylem conducts water and minerals from the roots towards
the aerial parts of the plant.
It also provides mechanical support.
The main components of xylem are:
tracheids, vessels, xylem parenchyma and xylem fibres.
π§ Reasoning Question:Why is xylem called a complex tissue?
Answer:Xylem contains different types of cells that work together
for conduction and support.
π Phloem
Phloem transports food, particularly sugars,
from regions where food is produced or available
to regions where it is required or stored.
The main components of phloem are:
sieve tubes, companion cells, phloem parenchyma and phloem fibres.
π§ Reasoning Question:Is phloem transport always downward?
Answer:No.Food is transported from a source to a sink.
Therefore, the direction depends on where food is produced
and where it is needed.
β Memory Rule:Xylem β Water + MineralsPhloem β Food
4. Types of Meristematic Tissue
Short Explanation:
Meristematic tissue is classified according to its position in the plant:
apical, intercalary and lateral meristem.
Type
Location
Main Function
Apical Meristem
Tips of roots and shoots
Increase in length
Intercalary Meristem
Base of leaves or internodes
Growth of particular regions
Lateral Meristem
Sides of stems and roots
Increase in girth/thickness
π§ Reasoning Question:A plant’s height increases rapidly. Which meristem is mainly responsible?
Answer:Apical meristem.It is present at the growing tips of roots and shoots and increases
the length of the plant.
π§ Reasoning Question:A stem becomes thicker as the plant grows older.
Which meristem is responsible?
Answer:Lateral meristem.It increases the girth or thickness of stems and roots.
π§ Reasoning Question:Why can grass regrow after being cut?
Answer:Intercalary meristematic regions can continue cell division
and produce new growth.
β Exam Memory Trick:
APICAL β A = Above / tip β LengthLATERAL β Side β GirthINTERCALARY β In-between regions β Growth
5. Permanent Tissue
Short Explanation:When meristematic cells stop dividing and become specialised
for specific functions, they form
permanent tissues.
The process by which cells become specialised in structure and function
is called differentiation.
Meristematic cells
Actively divide
Differentiated cells
Become specialised
Permanent tissue
Performs a specific function
π§ Reasoning Question:Why do permanent tissues generally stop dividing?
Answer:Their cells have differentiated and become specialised
for particular functions rather than continuous cell division.
π§ Reasoning Question:Are all permanent tissue cells dead?
Answer:No.Many permanent tissues contain living cells.
For example, parenchyma and collenchyma are living tissues.
Sclerenchyma cells are generally dead at maturity.
β Exam Alert:Do not write:“Permanent tissue means dead tissue.”That statement is incorrect.Permanent tissue means a tissue whose cells have
differentiated and generally lost the ability to divide.
6. Simple Permanent Tissues
Short Explanation:Simple permanent tissues are mainly made up of
one type of cell.The three important types are:Parenchyma, Collenchyma and Sclerenchyma.
πΏ Parenchyma
Storage and other basic functions.
Some forms perform photosynthesis.
π± Collenchyma
Provides support while allowing flexibility.
π³ Sclerenchyma
Provides strength and rigidity.
Feature
Parenchyma
Collenchyma
Sclerenchyma
Cells
Living
Living
Dead at maturity
Cell wall
Thin
Unevenly thickened
Very thick and lignified
Intercellular spaces
Usually present
Very little
Usually absent
Main role
Storage / photosynthesis
Support + flexibility
Strength + rigidity
πΏ Parenchyma
Parenchyma is a simple permanent tissue made up of living cells.
The cells generally have thin cell walls and may have intercellular spaces.
It commonly performs functions such as
storage.
When parenchyma contains chloroplasts, it can perform photosynthesis.
Such tissue is called chlorenchyma.
π§ Reasoning Question:Why is parenchyma suitable for storage?
Answer:Parenchyma cells are living and commonly have large vacuoles,
which can store substances such as food and water.
π§ Reasoning Question:A plant tissue contains parenchyma cells with chloroplasts.
What additional function can it perform?
Answer:It can perform photosynthesis because chloroplasts
contain chlorophyll.Such parenchyma is called chlorenchyma.
π Aerenchyma
In aquatic plants, parenchyma may contain large air spaces.
This specialised form is called aerenchyma.
π§ Reasoning Question:How can aerenchyma help an aquatic plant float?
Answer:The large air spaces provide buoyancy and help the plant remain
supported in water.
π± Collenchyma
Collenchyma consists of living cells whose walls are
unevenly thickened at the corners.
It provides mechanical support while allowing flexibility.
It is commonly found in young growing parts such as
leaf stalks and below the epidermis of stems.
π§ Reasoning Question:Why is collenchyma suitable for a young bending stem?
Answer:It provides mechanical support while retaining flexibility.
Therefore, the young stem can bend without easily breaking.
π§ Application Question:What would happen if a young plant part had only rigid tissue
and no flexible supporting tissue?
Answer:The plant part would be less flexible and could be more likely
to break when subjected to bending forces.
π³ Sclerenchyma
Sclerenchyma provides mechanical strength and rigidity.
Its cells generally have very thick walls containing
lignin and are dead at maturity.
Sclerenchymatous cells may occur in parts that need strong support,
such as fibres and the hard covering of some seeds and nuts.
π§ Reasoning Question:Why is sclerenchyma rigid?
Answer:Its cells have very thick, lignified walls.
Lignification makes the walls hard and provides mechanical strength.
π§ Reasoning Question:Why are sclerenchyma cells generally dead at maturity?
Answer:Their main role is mechanical strength.
The thick, lignified walls provide the required rigidity,
so the living contents are not essential when the cells mature.
Short Explanation:Complex permanent tissues contain
different types of cells
that work together to perform a common function.The two major complex tissues are:Xylem and Phloem.
π§ Xylem
Xylem conducts water and minerals from the roots towards
the aerial parts of the plant.
It also provides mechanical support.
The main components of xylem are:
tracheids, vessels, xylem parenchyma and xylem fibres.
π§ Reasoning Question:Why is xylem called a complex tissue?
Answer:Xylem contains different types of cells that work together
for conduction and support.
π Phloem
Phloem transports food, particularly sugars,
from regions where food is produced or available
to regions where it is required or stored.
The main components of phloem are:
sieve tubes, companion cells, phloem parenchyma and phloem fibres.
π§ Reasoning Question:Is phloem transport always downward?
Answer:No.Food is transported from a source to a sink.
Therefore, the direction depends on where food is produced
and where it is needed.
β Memory Rule:Xylem β Water + MineralsPhloem β Food
14. π― AssertionβReason Questions
Directions:
Read the Assertion (A) and Reason (R). Choose the correct option.
A. Both A and R are true, and R correctly explains A. B. Both A and R are true, but R does not correctly explain A. C. A is true, but R is false. D. A is false, but R is true.
Q1.Assertion:
Meristematic cells have dense cytoplasm.
Reason:
Meristematic cells are actively involved in cell division.
Answer: A
Both statements are true, and active cell division explains
the presence of dense cytoplasm.
Q2.Assertion:
Apical meristem increases the girth of a stem.
Reason:
Apical meristem is present at the tips of roots and shoots.
Answer: D
The assertion is false. Apical meristem mainly increases length.
The reason is true.
Q3.Assertion:
Collenchyma provides flexibility to young plant parts.
Reason:
Collenchyma cells have unevenly thickened cell walls.
Answer: A
The uneven thickening provides support while allowing flexibility.
Reason:
Sclerenchyma cells generally have thick, lignified walls.
Answer: A
Thick lignified walls provide rigidity and strength.
Q5.Assertion:
Blood is a connective tissue.
Reason:
Blood contains cells suspended in a fluid matrix.
Answer: A
Blood has cells embedded in plasma, its fluid matrix.
Q6.Assertion:
Cardiac muscles are voluntary muscles.
Reason:
Cardiac muscles are present in the heart.
Answer: D
Cardiac muscle is involuntary. The reason is true.
Q7.Assertion:
Squamous epithelium is suitable for gas exchange.
Reason:
Its cells are thin and flat.
Answer: A
Thin cells allow gases to diffuse over a short distance.
Q8.Assertion:
Xylem transports food from leaves.
Reason:
Phloem transports food from source to sink.
Answer: D
The assertion is false. Phloem transports food.
The reason is true.
15. π NCERT-Based MCQs
Try answering each question before opening the explanation.
Q1.
Which tissue is responsible for growth at the tips of roots?
A. Lateral meristem
B. Apical meristem
C. Sclerenchyma
D. Phloem
Answer: B β Apical meristem
Q2.
Which tissue increases the girth of stems?
A. Apical meristem
B. Intercalary meristem
C. Lateral meristem
D. Parenchyma
Answer: C β Lateral meristem
Q3.
Which simple permanent tissue provides flexibility?
A. Sclerenchyma
B. Collenchyma
C. Xylem
D. Phloem
Answer: B β Collenchyma
Q4.
Which tissue is mainly associated with storage?
A. Parenchyma
B. Sclerenchyma
C. Xylem
D. Nervous tissue
Answer: A β Parenchyma
Q5.
Which tissue has thick, lignified cell walls?
A. Parenchyma
B. Collenchyma
C. Sclerenchyma
D. Epithelium
Answer: C β Sclerenchyma
Q6.
Which tissue transports water and minerals?
A. Phloem
B. Xylem
C. Collenchyma
D. Epidermis
Answer: B β Xylem
Q7.
Which tissue transports food?
A. Xylem
B. Sclerenchyma
C. Phloem
D. Cartilage
Answer: C β Phloem
Q8.
Which epithelial tissue is made up of thin, flat cells?
A. Cuboidal
B. Columnar
C. Squamous
D. Glandular
Answer: C β Squamous epithelium
Q9.
Which tissue connects muscle to bone?
A. Ligament
B. Tendon
C. Cartilage
D. Areolar tissue
Answer: B β Tendon
Q10.
Which tissue connects bone to bone?
A. Tendon
B. Ligament
C. Adipose
D. Blood
Answer: B β Ligament
Q11.
Which is a fluid connective tissue?
A. Bone
B. Cartilage
C. Blood
D. Tendon
Answer: C β Blood
Q12.
Which muscle is involuntary and striated?
A. Skeletal muscle
B. Smooth muscle
C. Cardiac muscle
D. Tendon
Answer: C β Cardiac muscle
Q13.
Which muscle is spindle-shaped and non-striated?
A. Smooth muscle
B. Cardiac muscle
C. Skeletal muscle
D. Sclerenchyma
Answer: A β Smooth muscle
Q14.
The structural and functional unit of nervous tissue is:
A. Nephron
B. Neuron
C. Alveolus
D. Platelet
Answer: B β Neuron
Q15.
Which structure receives signals in a neuron?
A. Axon
B. Dendrites
C. Tendon
D. Plasma
Answer: B β Dendrites
16. π₯ HOTS β Think Beyond the Definition
Q1.
A plant has a tissue with living cells, thin walls and
large intercellular spaces. Which tissue is most likely present?
Answer:
Parenchyma. Its living cells generally have thin walls and
intercellular spaces.
Q2.
A tissue has living cells with uneven wall thickening
and provides flexible support. Identify it.
Answer:
Collenchyma.
Q3.
A tissue contains dead cells with extremely thick,
lignified walls. What function would you expect?
Answer:
Mechanical strength and rigidity. This indicates sclerenchyma.
Q4.
A student says, “Xylem only transports water and has no other role.”
Is this completely correct?
Answer:
No. Xylem also contributes to mechanical support because
some of its components provide strength.
Q5.
A tissue has a fluid matrix and transports oxygen,
nutrients and waste products. Identify it.
Answer:
Blood.
Q6.
Why is the lining of the intestine not made of sclerenchyma?
Answer:
The intestine requires living, specialised cells for functions
such as absorption and secretion. Sclerenchyma is a rigid,
supporting plant tissue and would not perform these functions.
Q7.
Why would replacing the alveolar lining with several thick
layers reduce gas exchange?
Answer:
A thicker barrier increases the diffusion distance, making
the movement of oxygen and carbon dioxide less efficient.
Q8.
A tissue is striated. Can you immediately conclude that it is
voluntary muscle?
Answer:
No. Both skeletal and cardiac muscles are striated.
Skeletal muscle is voluntary, whereas cardiac muscle is involuntary.
17. π Most Important Comparisons
Comparison
Difference
Meristematic vs Permanent
Meristematic cells actively divide;
permanent cells are differentiated and generally do not divide.
