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Tissues in Action

NCERT Class 9 · Science Based on NCERT Class 9 Science textbook · Free CBSE study kit

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Chapter Notes

Overview
This chapter explores how cells group together to form tissues, which then form organs and organ systems in multicellular organisms. It explains the differences between plant and animal tissues, focusing on their structure and function. The one big idea a student must walk away with is that tissues are specialized groups of similar cells that perform specific functions, enabling division of labour and increasing efficiency in complex life processes.
Key Concepts (35)
Tissue
A group of cells that are similar in structure and work together to perform a specific function.
e.g. Muscle tissue enables movement; nervous tissue carries messages to different parts of the body.
Meristematic tissue
A tissue consisting of actively dividing cells that are responsible for growth in plants.
e.g. The tips of roots and shoots contain meristematic tissue that helps the plant grow in length.
Apical meristem
Meristematic tissue located at the tips of roots and shoots that helps plants grow in length.
e.g. The root tip of an onion bulb contains apical meristem; cutting it stops root growth.
Lateral meristem
Meristematic tissue arranged in a ring in the stem that increases the girth or diameter of the plant.
e.g. The increase in thickness of a tree trunk over years is due to lateral meristem.
Intercalary meristem
Meristematic tissue located at the base of internodes or just above nodes that helps plants regenerate after cutting.
e.g. Grass grows again after being mowed due to intercalary meristem at the nodes.
Differentiation
The process by which meristematic tissue becomes specialized to perform specific functions, forming permanent tissues.
e.g. Cells from meristematic tissue lose the ability to divide and become parenchyma, collenchyma, or sclerenchyma.
Permanent tissues
Tissues that have lost the ability to divide and are specialized to perform specific functions such as support, transport, or storage.
e.g. Parenchyma, collenchyma, and sclerenchyma are simple permanent tissues; xylem and phloem are complex permanent tissues.
Simple permanent tissues
Permanent tissues composed of only one type of cell.
e.g. Parenchyma, collenchyma, and sclerenchyma are simple permanent tissues.
Complex permanent tissues
Permanent tissues composed of more than one type of cell working together.
e.g. Xylem and phloem are complex permanent tissues.
Parenchyma
A simple permanent tissue consisting of living cells with thin walls, loosely packed with intercellular spaces, mainly for storage and photosynthesis.
e.g. In aquatic plants, specialized parenchyma forms air spaces that help them float.
Collenchyma
A simple permanent tissue consisting of living cells with unevenly thickened corners due to pectin deposition, providing support and flexibility.
e.g. The leaf stalks of coriander are soft and flexible due to collenchyma.
Sclerenchyma
A simple permanent tissue consisting of cells with thick walls due to lignin deposition, making them hard and strong; most cells are dead.
e.g. Coconut husk fibres are hard and brittle due to sclerenchyma.
Xylem
A complex permanent tissue that transports water and minerals from roots to other parts of the plant and provides strength.
e.g. Water reaches the leaves of tall trees through xylem.
Phloem
A complex permanent tissue that transports food from leaves to other parts of the plant.
e.g. Food prepared in leaves reaches roots and other parts through phloem.
Epidermis
The outermost layer of the plant body, consisting of a tightly packed single layer of flat and rectangular cells, covered with a waxy cuticle for protection.
e.g. The epidermis protects plants from mechanical injury, water loss, and harmful microorganisms.
Cuticle
A waxy layer of cutin covering the epidermis that reduces water loss and provides protection.
e.g. Desert plants have a thick cuticle to reduce water loss.
Stomata
Pores in the epidermis of leaves that allow gaseous exchange and transpiration.
e.g. Stomata help in the exchange of oxygen and carbon dioxide during photosynthesis.
Epithelial tissue
Animal tissue that forms the outer covering of the body and lines internal organs, composed of closely packed cells with little intercellular space.
e.g. Skin is made of epithelial tissue that prevents entry of germs.
Connective tissue
Animal tissue that connects and supports other tissues, characterized by a matrix that may be fluid, soft, or hard.
e.g. Blood, bone, cartilage, tendon, and ligament are connective tissues.
Muscular tissue
Animal tissue responsible for movement, consisting of cells that can contract.
e.g. Skeletal muscles help in voluntary movements like running.
Nervous tissue
Animal tissue that forms the body's control and coordination network, consisting of neurons that receive and transmit impulses.
e.g. The brain and nerves are made of nervous tissue.
Neuron
The structural and functional unit of nervous tissue, specialized to receive, process, and transmit messages.
e.g. A neuron has a cell body, dendrites, and an axon.
Skeletal muscle
Voluntary muscle attached to the skeleton, made of long, cylindrical, unbranched, multinucleate, striated fibres.
e.g. Muscles in the arms and legs are skeletal muscles.
Smooth muscle
Involuntary muscle found in organs like the stomach and intestines, with spindle-shaped cells, a single nucleus, and no striations.
e.g. The movement of food in the intestine is due to smooth muscles.
Cardiac muscle
Involuntary muscle found only in the heart, with cylindrical, branched fibres, a single nucleus, and faint striations, working tirelessly without fatigue.
e.g. The beating of the heart is due to cardiac muscle.
Tendon
A connective tissue that connects muscle to bone, made of tough fibres that transmit force.
e.g. The Achilles tendon connects calf muscles to the heel bone.
Ligament
A connective tissue that connects bone to bone, providing stability and limiting movement.
e.g. Ligaments in the knee prevent dislocation of the joint.
Joint
A junction between two or more bones that allows movement.
e.g. The elbow is a hinge joint that allows bending and straightening.
Ball and socket joint
A joint where the rounded top of one bone fits into a shallow hollow of another, allowing free movement in all directions.
e.g. The shoulder joint is a ball and socket joint.
Hinge joint
A joint that allows movement in one direction only, like a door hinge.
e.g. The elbow and knee are hinge joints.
Pivot joint
A joint that allows rotation, such as the movement of the head side to side.
e.g. The neck has a pivot joint connecting the skull to the backbone.
Fixed joint
A joint where bones are connected and cannot move, providing protection.
e.g. The bones of the skull are joined by fixed joints.
Vertebral column
The backbone or spine, made up of a series of small bones called vertebrae, supporting the body and protecting the spinal cord.
e.g. Between each vertebra is a cartilage disc that acts as a cushion.
Rib cage
A protective cage formed by 12 pairs of ribs, attached to the spine and breastbone, protecting the heart and lungs.
e.g. The rib cage expands and contracts during breathing.
Totipotency
The ability of a mature plant cell to undifferentiate, divide, and redifferentiate into a complete plant under specific conditions.
e.g. F. C. Steward demonstrated totipotency using phloem cells of carrot.
Formulas & Equations (2)
Bone mass percentage = (Bone weight / Total body weight) × 100
Reads as: Bone mass percentage equals bone weight divided by total body weight, multiplied by 100
Variables: Bone weight (kg), Total body weight (kg)
Use when: When estimating the percentage of body weight contributed by bones in Activity 3.4
⚠ Students forget to multiply by 100 to get a percentage, or they use the wrong units (e.g., grams instead of kilograms).
Muscle mass percentage = (Muscle weight / Total body weight) × 100
Reads as: Muscle mass percentage equals muscle weight divided by total body weight, multiplied by 100
Variables: Muscle weight (kg), Total body weight (kg)
Use when: When estimating the percentage of body weight contributed by muscles in Activity 3.4
⚠ Students often confuse bone and muscle percentages, or they do not account for individual variation based on age, gender, and body composition.
How It Works
Growth in length of plants (Apical meristem activity)
  1. Step 1: Cells at the tips of roots and shoots (apical meristem) divide continuously.
  2. Step 2: New cells are added at the tips, increasing the length of the root or shoot.
  3. Step 3: If the tip is cut, growth in length stops, as shown in the onion root experiment (Activity 3.1).
💡 Only the tips of roots and shoots contain apical meristem; cutting the tip stops length growth.
Growth in girth of plants (Lateral meristem activity)
  1. Step 1: Actively dividing cells arranged in a ring in the stem (lateral meristem) divide.
  2. Step 2: New cells are produced inside and outside in a concentric manner.
  3. Step 3: This increases the diameter or girth of the stem over time, forming annual growth rings.
💡 Lateral meristem is responsible for increase in girth, not length; annual rings reflect growth conditions each year.
Regrowth after cutting (Intercalary meristem activity)
  1. Step 1: Intercalary meristem is located at the base of internodes or just above nodes.
  2. Step 2: When the tip of a stem is cut or grass is mowed, intercalary meristem cells divide.
  3. Step 3: New branches or shoots arise from the nodes, allowing the plant to regenerate.
💡 Intercalary meristem is found in grasses and allows regrowth after grazing or cutting.
Differentiation of meristematic tissue into permanent tissue
  1. Step 1: Meristematic cells divide continuously, adding new cells to the plant body.
  2. Step 2: Some newly formed cells lose the ability to divide.
  3. Step 3: These cells undergo changes in structure and function, becoming specialized (e.g., parenchyma, collenchyma, sclerenchyma).
  4. Step 4: This process is called differentiation, and the resulting cells form permanent tissues.
💡 Differentiation is irreversible; once cells become permanent, they cannot divide again.
Transport of water and minerals by xylem
  1. Step 1: Water and minerals are absorbed by roots from the soil.
  2. Step 2: Xylem, consisting of tracheids and vessels (tubular, thick-walled, dead cells), transports water and minerals upward.
  3. Step 3: Transpiration from leaves creates a transpiration pull that helps water move against gravity.
  4. Step 4: Xylem also provides strength to the plant.
💡 Xylem cells are mostly dead, and water transport is driven by transpiration pull.
Transport of food by phloem
  1. Step 1: Food is synthesized in leaves during photosynthesis.
  2. Step 2: Sieve tubes (long, tubular cells joined end to end by perforated walls) transport food.
  3. Step 3: Companion cells regulate the loading and unloading of sugars in sieve tubes.
  4. Step 4: Food is transported to all parts of the plant, including roots and storage organs.
💡 Phloem is mostly made of living cells; sieve tubes are living but lack nuclei, and companion cells support them.
Muscle contraction and movement
  1. Step 1: Muscles receive instructions from the nervous system via neurons.
  2. Step 2: Skeletal muscles contract, pulling on tendons attached to bones.
  3. Step 3: Tendons transmit the force to bones, causing movement at a joint.
  4. Step 4: Ligaments connect bones to bones, providing stability and limiting excessive movement.
💡 Muscles can only pull, not push; they work in pairs (agonist and antagonist) to produce movement.
Nerve impulse transmission
  1. Step 1: Dendrites of a neuron receive signals from other neurons or sensory receptors.
  2. Step 2: The cell body processes the signal.
  3. Step 3: The axon carries the message away from the cell body to the axon terminals.
  4. Step 4: Axon terminals transmit the message to other cells (e.g., muscles, glands, or other neurons).
💡 Neurons are specialized for communication; dendrites receive, axon transmits.
Breathing and rib cage movement
  1. Step 1: The rib cage is made of 12 pairs of ribs attached to the spine and breastbone by flexible cartilage.
  2. Step 2: During inhalation, muscles contract, expanding the rib cage.
  3. Step 3: This increases space in the chest, allowing air to move into the lungs.
  4. Step 4: During exhalation, the rib cage contracts, pushing air out.
💡 The flexibility of cartilage allows the rib cage to expand and contract during breathing.
Exam Traps — Don't Make These Mistakes
⚠ Confusing xylem and phloem functions
✗ Xylem transports food and phloem transports water.
→ This is the opposite of the correct function. Xylem transports water and minerals; phloem transports food.
✓ Xylem transports water and minerals from roots to other parts of the plant, while phloem transports food from leaves to other parts.
⚠ Thinking all meristematic cells are at root and shoot tips only
✗ Meristematic cells are located only at the root and shoot apices.
→ This ignores lateral meristem (for girth) and intercalary meristem (for regrowth). Meristematic tissues are also present along the circumference of stems and at nodes.
✓ Meristematic tissues are found at root and shoot tips (apical meristem), along the circumference of stems (lateral meristem), and at the base of internodes or nodes (intercalary meristem).
⚠ Confusing tendon and ligament
✗ Tendons connect bone to bone, and ligaments connect muscle to bone.
→ This is reversed. Tendons connect muscle to bone; ligaments connect bone to bone.
✓ Tendons connect muscle to bone and transmit force for movement. Ligaments connect bone to bone and provide stability to joints.
⚠ Thinking all cells in xylem are living
✗ Xylem is made of living cells that transport water.
→ Most xylem cells (tracheids, vessels, xylem fibres) are dead and sclerenchymatous. Only xylem parenchyma is living.
✓ Xylem consists of tracheids, vessels, xylem fibres (all dead), and xylem parenchyma (living). The dead cells form tubes for water transport.
⚠ Confusing voluntary and involuntary muscles
✗ Cardiac muscle is voluntary because we can control our heartbeat.
→ Cardiac muscle is involuntary; we cannot consciously control our heartbeat. Skeletal muscles are voluntary.
✓ Skeletal muscles are voluntary (under conscious control), while smooth and cardiac muscles are involuntary (not under conscious control).
⚠ Thinking all epithelial tissues are for protection only
✗ Epithelial tissue only protects the body.
→ Epithelial tissue also performs exchange, secretion, absorption, and sensory functions depending on its structure and location.
✓ Epithelial tissue performs multiple functions: protection (skin), exchange (lungs), secretion (glands), absorption (intestine), and sensory (taste buds).
Compare & Contrast
Function
Xylem
Phloem
Xylem transports water and minerals from roots to other parts; phloem transports food from leaves to other parts.
Connection
Tendon
Ligament
Tendon connects muscle to bone; ligament connects bone to bone.
Location and function
Apical meristem
Lateral meristem
Apical meristem is at root and shoot tips and increases length; lateral meristem is along the circumference of stems and increases girth.
Control and structure
Skeletal muscle
Cardiac muscle
Skeletal muscle is voluntary, striated, multinucleate, and unbranched; cardiac muscle is involuntary, faintly striated, uninucleate, and branched.
Cell wall and function
Parenchyma
Collenchyma
Parenchyma has thin walls and stores food; collenchyma has unevenly thickened corners due to pectin and provides flexibility.
Cell wall composition and living/dead
Collenchyma
Sclerenchyma
Collenchyma has living cells with pectin-thickened corners; sclerenchyma has dead cells with lignin-thickened walls, making them hard.
Exam Focus
Marks pattern: 2 MCQs (1 mark each), 1 SA (3 marks), 1 LA (5 marks) — total 10 marks typically
Most asked: Types of meristematic tissues and their functions · Simple permanent tissues (parenchyma, collenchyma, sclerenchyma) — structure and function · Complex permanent tissues (xylem and phloem) — components and functions · Epithelial tissue types and their locations · Connective tissues (blood, bone, cartilage, tendon, ligament) · Muscle types (skeletal, smooth, cardiac) · Neuron structure and function · Types of joints (ball and socket, hinge, pivot, fixed)
Don't skip: Differentiate between xylem and phloem (3 marks); Explain the structure and function of any two simple permanent tissues (3 marks); Describe the types of meristematic tissues with their locations and functions (5 marks); Compare and contrast skeletal, smooth, and cardiac muscles (5 marks); Explain the structure of a neuron and its function (3 marks)
One-Line Revision (read aloud before the exam)
  1. A tissue is a group of similar cells that work together to perform a specific function.
  2. Meristematic tissues are actively dividing cells responsible for growth in plants.
  3. Apical meristem at root and shoot tips increases length; lateral meristem increases girth; intercalary meristem allows regrowth after cutting.
  4. Differentiation is the process by which meristematic cells become specialized permanent tissues.
  5. Simple permanent tissues include parenchyma (storage), collenchyma (flexibility), and sclerenchyma (strength).
  6. Xylem transports water and minerals; phloem transports food.
  7. Xylem consists of tracheids, vessels, xylem fibres (dead), and xylem parenchyma (living).
  8. Phloem consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibres.
  9. Epithelial tissue covers the body and lines organs; it performs protection, exchange, secretion, absorption, and sensory functions.
  10. Connective tissues include blood, bone, cartilage, tendon, and ligament.
  11. Tendons connect muscle to bone; ligaments connect bone to bone.
  12. Skeletal muscle is voluntary and striated; smooth muscle is involuntary and non-striated; cardiac muscle is involuntary and faintly striated.
  13. Neurons have dendrites (receive signals), a cell body (processes signals), and an axon (transmits signals).
  14. Ball and socket joints allow movement in all directions; hinge joints allow movement in one plane; pivot joints allow rotation; fixed joints allow no movement.
  15. The rib cage protects the heart and lungs and expands/contracts during breathing.
  16. Totipotency is the ability of a mature plant cell to regenerate a whole plant, as demonstrated by F. C. Steward with carrot phloem cells.

MCQs — 10 Questions with Answers

Q1. Which of the following is the correct definition of a tissue?

  • A. A group of similar cells performing similar functions together ✓
  • B. Any collection of cells in an organism
  • C. A single type of cell in the body
  • D. An organ formed by different types of tissues

Answer: A — A tissue is specifically defined as similar cells grouped together to perform a specific function, which is the basis of division of labour.

Q2. In the onion root growth experiment, what was the main observation in Jar B after cutting the root tips on day 3?

  • A. Roots grew faster than in Jar A
  • B. Roots stopped growing but resumed growth after a few days
  • C. Roots did not grow further after the tip was cut ✓
  • D. New roots grew from the middle of the original root

Answer: C — The apical meristem (actively dividing cells) at the root tip was removed, so the root could not grow further.

Q3. Which type of meristem is responsible for the increase in girth or diameter of tree stems?

  • A. Apical meristem
  • B. Lateral meristem ✓
  • C. Intercalary meristem
  • D. Vascular meristem

Answer: B — Lateral meristem consists of cells arranged in rings that divide to produce new cells inward and outward, increasing stem diameter.

Q4. Why do plant cells have a cell wall while animal cells do not?

  • A. Plant cells are larger than animal cells
  • B. Plants are fixed in one place and need structural support; animals move and need flexible cells ✓
  • C. Animal cells perform photosynthesis and do not need a cell wall
  • D. The cell wall helps animal cells digest food more efficiently

Answer: B — The cell wall provides rigidity for stationary plants; animal cells without walls can change shape easily, enabling locomotion.

Q5. What information can scientists obtain by counting annual growth rings on a cut tree trunk?

  • A. Only the age of the tree
  • B. Only the climatic conditions during the tree's life
  • C. The age of the tree and the climatic conditions (favourable or unfavourable) during each year ✓
  • D. The type of soil in which the tree grew

Answer: C — Each ring represents one year; wide rings indicate good growing conditions, narrow rings indicate poor conditions, so age and climate history both can be determined.

Q6. Which of the following statements about xylem and phloem is NOT correct?

  • A. Xylem transports water and minerals from roots to other parts
  • B. Phloem transports food (sugars) synthesised during photosynthesis
  • C. Xylem transports food and phloem transports water ✓
  • D. Both xylem and phloem are conducting tissues in plants

Answer: C — This is backwards; xylem transports water and minerals, while phloem transports food—reversing their functions makes the statement incorrect.

Q7. A plant seedling is placed in a dark room where photosynthesis cannot occur. If the plant develops tissues normally but lacks xylem tissue, which consequence is most likely?

  • A. The plant cannot synthesise food
  • B. The plant cannot absorb water and minerals from the soil efficiently ✓
  • C. The plant cannot transport sugars to growing regions
  • D. The plant cannot produce chlorophyll

Answer: B — Xylem specifically transports water and minerals; without it, the plant cannot distribute these essential materials from roots to other parts.

Q8. In the hierarchy of organisation, at which level does division of labour become possible?

  • A. At the cellular level only
  • B. When cells group into tissues ✓
  • C. Only when organs are formed
  • D. At the organ system level

Answer: B — Division of labour begins when similar cells group into tissues with specific functions, allowing different tissues to perform different tasks efficiently.

Q9. Ramesh observes that after he cuts the grass in his lawn, new grass grows back from the base within a few weeks. Which type of meristem allows this regrowth?

  • A. Apical meristem at the shoot tip
  • B. Lateral meristem in the stem
  • C. Intercalary meristem located at the base of grass leaves ✓
  • D. Vascular meristem in the roots

Answer: C — Intercalary meristem, located at the base of leaf blades in grasses, is responsible for regrowth after the shoot tips are removed by cutting or grazing.

Q10. If a plant's apical meristem is damaged but its lateral meristem remains intact, which of the following would most likely occur?

  • A. The plant stops all growth immediately
  • B. The plant cannot grow taller but can still increase in girth
  • C. The plant grows only in girth and eventually becomes a thick bush ✓
  • D. The lateral meristem transforms into an apical meristem to replace the damaged one

Answer: C — Without apical meristem, vertical growth stops, but lateral meristem continues to produce new cells radially, creating a short, thick, bushy appearance.

Flashcards

What is a tissue?

A group of similar cells that work together to perform a specific function.

Name the type of meristem responsible for plant growth in length.

Apical meristem, located at the tips of roots and shoots.

Why do plant cells have a cell wall but animal cells do not?

Plants are fixed in place and need structural support; animals move and need flexible cells.

What happens when the root tip of an onion is cut?

Root growth stops because the apical meristem (actively dividing cells) at the tip is removed.

Which meristem causes trees to increase in diameter or girth?

Lateral meristem, which divides in a ring-like pattern around the stem.

What do annual growth rings in a tree trunk represent?

Each ring represents one year of growth; wide rings indicate favourable conditions, narrow rings indicate unfavourable conditions.

Name two conducting tissues in plants and their functions.

Xylem transports water and minerals; phloem transports food (sugars) to different parts.

How is the hierarchy of organisation organised in multicellular organisms?

Cells group into tissues, tissues form organs, organs form organ systems, and organ systems form an organism.

What is division of labour in tissues?

Different groups of cells performing different functions, which increases body efficiency and enables complex life processes.

Why do some tissues grow throughout life while others do not?

Tissues with meristematic cells (like plant meristems) can grow throughout life; tissues without actively dividing cells cannot grow after maturity.

Important Board Questions

Define tissue and explain why division of labour at the tissue level is important for multicellular organisms. [2 marks]

State that a tissue is a group of similar cells performing a specific function. Explain that different tissues performing different functions increases overall body efficiency and enables complex life processes.

Describe the onion root growth experiment and explain what the results show about the location of growth in roots. Why does growth stop after cutting the root tip? [3 marks]

Describe the setup: two jars with onion bulbs, roots measured daily, Jar B roots cut on day 3. Results show Jar A grows continuously while Jar B stops. Explain that actively dividing cells (apical meristem) are only at the tip, so cutting removes the growth zone.

Explain how plants differ from animals in tissue structure and function, relating these differences to their modes of life and nutrition. Use specific examples of tissues and their functions. [5 marks]

Compare: plants are fixed (need rigid cell wall for support), animals move (need flexible cells without rigid walls). Plants synthesise food (xylem and phloem for water/mineral and food transport), animals digest obtained food (need digestive tissues). Explain how structure (cell wall, meristems) relates to function (support, growth patterns, nutrient transport). Use xylem/phloem and meristem examples.

Assertion-Reason Questions for Tissues in Action

Q1. Assertion (A):

Apical meristem is responsible for the increase in length of roots and shoots in plants.

Reason (R):

Apical meristem contains actively dividing cells located at the tips of roots and shoots that produce new cells in a way that increases the plant's height and root depth.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason correctly explains why apical meristem is responsible for length increase. The presence of actively dividing cells at tips is the direct cause of elongation.

Q2. Assertion (A):

Annual growth rings in a tree trunk indicate the age and growth conditions of the tree.

Reason (R):

These rings are produced by apical meristem activity at the shoot tips over many years.

Answer: C — A is true but R is false — The assertion is true—rings do indicate age and conditions. However, the reason is false because annual rings are produced by lateral meristem, not apical meristem. Lateral meristem creates the concentric rings, while apical meristem causes length growth.

Q3. Assertion (A):

Plant tissues and animal tissues have different structures because plants are stationary while animals are mobile.

Reason (R):

Plant cells have cell walls providing rigidity for support, whereas animal cells lack cell walls and can change shape easily to enable movement and locomotion.

Answer: A — Both A and R are true, and R is the correct explanation of A — Both assertion and reason are true. The mobility difference between organisms is a direct cause of structural tissue differences, with cell wall presence/absence being the key structural adaptation explained by functional needs.

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Case-Based Questions (CBQ) for Tissues in Action

Case Study:

A botanist conducted an experiment with two identical snapdragon seedlings. Seedling A was kept intact with all its parts. Seedling B had its apical meristem (shoot tip) carefully removed under a microscope on Day 1. Both seedlings were grown under identical conditions with adequate water and sunlight. The botanist measured the height of both seedlings every two days for 14 days and recorded data showing that Seedling A increased in height continuously while Seedling B showed no increase in height after the removal, though some lateral buds began to develop nodes along the remaining stem.

Q1. What does the difference in height increase between Seedling A and Seedling B demonstrate about apical meristem?

  • A. Apical meristem is not necessary for plant growth
  • B. Apical meristem is responsible for increase in plant height and its removal prevents lengthwise growth ✓
  • C. Apical meristem controls the formation of lateral buds
  • D. Apical meristem prevents lateral bud development

Answer: B

Q2. Why did lateral buds develop in Seedling B even though the shoot tip was removed?

  • A. Lateral buds are produced by intercalary meristem located at nodes along the stem ✓
  • B. The lateral buds regenerated the apical meristem
  • C. Apical meristem somehow regenerated underground
  • D. Lateral meristem activity increased to compensate for the removal

Answer: A

Q3. If the lateral buds that developed in Seedling B were allowed to continue growing, what type of tissue would these lateral buds contain?

  • A. Only dermal tissue for protection
  • B. Apical meristem at their tips enabling growth in length ✓
  • C. Only vascular tissue for transport
  • D. Ground tissue for structural support

Answer: B

Q4. What would be the most likely outcome if the lateral buds in Seedling B were pinched off repeatedly?

  • A. New lateral buds would form indefinitely from intercalary meristem
  • B. The seedling would eventually produce a new shoot tip from the base
  • C. The seedling would remain stunted in height because no apical meristem exists to resume height growth ✓
  • D. The plant would develop deeper roots to compensate

Answer: C

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