Class 9 Science: Tissues in Action — Chapter Question Set

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structure

labour

apical

lateral

differentiation

cuticle

stomata

Collenchyma

lignin

xylem parenchyma

Sieve

haemoglobin

Tendons; ligaments

fatigue

pivot

False (Vacuoles are generally absent; cells have dense cytoplasm, thin walls and a prominent nucleus.)

True

True

False (Most sclerenchyma cells are dead, with thick lignified walls.)

False (Phloem transports food; xylem transports water and minerals.)

True

True

False (Cartilage has a soft, jelly-like matrix providing flexibility and cushioning.)

False (Tendons connect muscle to bone; ligaments connect bone to bone.)

False (Skeletal muscles are voluntary and striated; smooth muscles are involuntary and non-striated.)

True

True

False (The shoulder joint is a ball and socket joint.)

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True

A–2, B–1, C–4, D–5, E–3

A–2, B–3, C–1, D–4, E–5

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A tissue is a group of similar cells that work together to perform a specific function. The formation of different tissues leads to a division of labour in multicellular organisms, increasing efficiency and enabling complex life processes to be carried out effectively.

Plants are fixed in one place and need rigid cell walls for support, whereas animals move and require flexible cells. Their modes of nutrition also differ — plants make food by photosynthesis, while animals obtain food by ingestion — so the tissues they need are different.

Apical meristem is located at the root and shoot tips and increases length; lateral meristem lies along the circumference of stems and increases girth; intercalary meristem is found at the base of internodes or above nodes and helps in regeneration.

Meristematic cells are small with thin cell walls, a large prominent nucleus and dense cytoplasm. They are tightly packed with little or no intercellular space, and vacuoles are generally absent.

Differentiation is the process by which meristematic cells lose the ability to divide and become specialised to form permanent tissues with specific functions. For example, meristematic cells may differentiate into parenchyma, which is specialised for storage.

Parenchyma has thin cell walls, is loosely packed and mainly stores food. Collenchyma has unevenly thickened corners due to pectin deposition, which provides mechanical support and flexibility to the plant.

Sclerenchyma cells become dead because their walls are thickened with lignin, making them hard and non-living. They are found in stems, the veins of leaves, and the hard coverings of seeds and nuts such as the coconut husk and walnut shell.

Xylem transports water and minerals from roots to other parts of the plant and is made mostly of dead cells, except for xylem parenchyma. Phloem transports food from leaves to other parts and is made mostly of living cells, except for phloem fibres.

Companion cells are specialised parenchyma cells that regulate the functions of sieve tube cells, which lack a nucleus. They monitor the loading and unloading of sugars into the sieve tubes, helping in the transport of food.

The dermal tissue system forms the outer covering and protects the plant while reducing water loss; the ground tissue system makes up the main body between the dermal and vascular tissues and supports storage and photosynthesis; the vascular tissue system, consisting of xylem and phloem, conducts water, minerals and food.

The cuticle is a waxy layer of cutin that reduces water loss and protects the plant from injury. Stomata are pores in the epidermis that allow gaseous exchange and transpiration.

Bone has a rigid matrix rich in calcium and phosphorus, making it hard and strong. Cartilage has a soft, jelly-like matrix that provides flexibility and cushioning at joints.

Tendons connect muscle to bone and transmit the force needed for movement. Ligaments connect bone to bone, providing stability to joints and preventing dislocation.

Skeletal muscle is voluntary, cylindrical, unbranched, multinucleate and striated, and is attached to the skeleton. Smooth muscle is involuntary, spindle-shaped, with a single nucleus and no striations, and is found in the walls of organs such as the stomach and intestines.

Cardiac muscle is found only in the heart and is made of cylindrical, branched cells with a single nucleus and faint striations. It works tirelessly and rhythmically throughout life without fatigue, ensuring continuous pumping of blood.

A neuron has a cell body that contains the nucleus and controls its activities, dendrites that receive signals, and a long axon that carries messages away from the cell body, ending at axon terminals.

The musculoskeletal system is the framework of bones, muscles, joints, cartilage, tendons and ligaments that works under nervous control. It helps the body stand upright, move, maintain posture and protect internal organs.

In a ball and socket joint, the rounded end of one bone fits into a hollow of another, allowing movement in many directions, as in the shoulder and hip. In a hinge joint, movement is possible in only one direction, as in the elbow and knee.

The rib cage protects vital organs such as the heart and lungs. It is flexible because the ribs are joined to the sternum and spine by flexible cartilage, allowing the cage to expand and contract during breathing.

Totipotency is the ability of mature plant cells to regenerate into a complete plant under suitable conditions. It was demonstrated by F. C. Steward in 1958 using carrot phloem cells.

Introduction: Meristematic tissues are groups of actively dividing cells responsible for plant growth.
Key Points:
1. Apical meristem — Located at root and shoot tips; responsible for increase in length of the plant.
2. Lateral meristem — Located along the circumference of stems; responsible for increase in girth or thickness.
3. Intercalary meristem — Located at the base of internodes or above nodes; helps plants regenerate after cutting, e.g., in grasses.
Conclusion: Together, these three meristems account for growth in length, girth and branching in plants.

Introduction: Parenchyma is a simple permanent tissue made of living cells that performs multiple functions in plants.
Key Points:
1. Thin-walled living cells — Cells have thin walls and are loosely packed with intercellular spaces between them.
2. Food storage and photosynthesis — Mainly stores food but also performs photosynthesis in green parts of the plant.
3. Aquatic plant adaptation — In aquatic plants, specialised parenchyma forms air spaces that help the plants float.
Conclusion: Parenchyma is a versatile tissue that supports storage, photosynthesis and buoyancy in plants.

Introduction: Xylem is a complex permanent tissue that transports water and minerals from roots to other parts of the plant.
Key Points:
1. Components — Consists of tracheids, vessels, xylem parenchyma and xylem fibres; tracheids and vessels are tubular and thick-walled.
2. Living and dead cells — Xylem parenchyma is the only living component; tracheids, vessels and xylem fibres are primarily sclerenchymatous (dead).
3. Transport and strength — Transports water and minerals upwards and also provides mechanical strength to the plant.
Conclusion: Xylem is essential for water conduction and structural support in plants, especially in tall trees.

Introduction: Phloem is a complex permanent tissue that transports food from leaves to other parts of the plant.
Key Points:
1. Components — Consists of sieve tubes, companion cells, phloem parenchyma and phloem fibres; mostly made of living cells.
2. Sieve tubes and companion cells — Sieve tubes are long, tubular cells joined by perforated walls that transport food; companion cells regulate their function.
3. Storage and support — Phloem parenchyma stores food, resin, tannins and latex; phloem fibres provide strength.
Conclusion: Phloem is vital for distributing food and nutrients throughout the plant, supporting all its parts.

Introduction: Epithelial tissue forms the outer covering of the body and lines internal organs, with different types adapted for specific functions.
Key Points:
1. Squamous (flat) epithelium — Single layer of thin, flat cells for rapid diffusion of gases and liquids; found in blood vessels and lungs.
2. Stratified epithelium — Many layers of flat cells for protection from injury and microbes; found in skin, mouth and oesophagus.
3. Columnar epithelium — Tall, pillar-like cells for efficient absorption; found in the lining of the small intestine.
Conclusion: The structure of each epithelial type is specialised to suit its function of exchange, protection, secretion or absorption.

Introduction: Blood is a fluid connective tissue that connects different parts of the body by transporting nutrients, gases and hormones.
Key Points:
1. Plasma — The fluid part (about 55% of blood volume) that carries dissolved substances throughout the body.
2. Red Blood Cells — Contain haemoglobin, an iron-rich protein giving blood its red colour; transport oxygen; live about 4 months and are replaced regularly.
3. White Blood Cells and Platelets — WBCs collect at infected areas causing inflammation and pus formation; platelets help in blood clotting at injury sites.
Conclusion: Blood's components work together to transport materials, fight infection and prevent blood loss, connecting the body's systems.

Introduction: Muscular tissue produces voluntary and involuntary movements for locomotion and other body functions.
Key Points:
1. Skeletal muscles — Voluntary, attached to skeleton; cylindrical, unbranched, multinucleate, striated cells; enable running, writing and lifting.
2. Smooth muscles — Involuntary; spindle-shaped, single nucleus, non-striated; found in stomach and intestines for slow, continuous movements like digestion.
3. Cardiac muscles — Involuntary; found only in the heart; cylindrical, branched, single nucleus, faint striations; work rhythmically without fatigue.
Conclusion: Each muscle type is structurally adapted to its specific function — voluntary movement, digestion or the ceaseless beating of the heart.

Introduction: Neurons are the cells of nervous tissue, specialised to receive, process and transmit messages throughout the body.
Key Points:
1. Cell body — Contains the nucleus and controls all cell activities; acts as the control centre of the neuron.
2. Dendrites — Branch-like structures that receive signals from other neurons and pass them to the cell body.
3. Axon — A long fibre that carries messages away from the cell body, ending at axon terminals that transmit messages to other cells.
Conclusion: Neurons form the body's control and coordination network, enabling rapid communication between the brain and the body.

Introduction: Joints are junctions between two or more bones that allow different types of movement in the body.
Key Points:
1. Ball and socket joint — Rounded bone fits into a shallow hollow, allowing forward, backward, sideways and circular movements; e.g., shoulder and hip.
2. Hinge joint — Allows bending and straightening in one direction only, like a door hinge; e.g., elbow and knee.
3. Pivot joint and fixed joint — Pivot allows side-to-side rotation like the skull on the backbone; fixed joints in the skull cannot move, protecting the brain.
Conclusion: Different joint types enable the wide range of movements our body can make while providing stability and protection.

Introduction: The skeletal system consists of a framework of bones that provides strength and protects delicate internal organs.
Key Points:
1. Vertebral column — A flexible column of small bones (vertebrae) extending from the skull base, supporting the body and enabling upright posture.
2. Rib cage — 12 pairs of ribs forming a protective cage for the heart and lungs; flexible cartilage allows expansion during breathing.
3. Cartilage discs — Between each vertebra, cushioning and allowing flexibility so we can bend and twist without injuring the spinal cord.
Conclusion: The skeletal system protects vital organs, supports the body and works with muscles to enable movement.

Introduction: The epidermis is the outermost protective layer of the plant body, consisting of tightly packed cells.
Key Points:
1. Cuticle protection — Covered with a waxy layer of cutin called cuticle that reduces water loss and protects against mechanical injury and parasites.
2. Stomata — Pores in the leaf epidermis that allow gaseous exchange and transpiration, the evaporation of water vapour.
3. Root hair — Hair-like projections from epidermal cells in roots increase surface area for absorption of water and minerals from the soil.
Conclusion: The epidermis with its cuticle, stomata and root hair protects the plant and facilitates essential exchanges with the environment.

Introduction: The musculoskeletal system made up of bones, muscles, joints, cartilage, tendons and ligaments enables movement.
Key Points:
1. Muscle-bone connection — Muscles are attached to bones by tendons; when a muscle contracts, the tendon transmits force to the bone.
2. Joint movement — Movement occurs at joints where two or more bones meet; different joint types allow different ranges of motion.
3. Nervous control — The entire system functions under the control of the nervous system, which sends signals to muscles to contract or relax.
Conclusion: The coordinated action of muscles, bones and joints under nervous control produces all body movements.

Introduction: Totipotency is the ability of mature plant cells to regenerate a complete plant under suitable conditions.
Key Points:
1. Steward's experiment — In 1958, F. C. Steward cultured phloem cells of carrot in a nutrient medium with sugars and hormones.
2. Dedifferentiation and redifferentiation — Cells first dedifferentiated into an unspecialised mass, then divided and redifferentiated into roots, shoot and eventually a complete plant.
3. Significance — Shows that some mature plant cells retain the ability to undifferentiate, divide and redifferentiate, similar to how a zygote develops into an organism.
Conclusion: Totipotency demonstrates the remarkable regenerative capacity of plant cells and laid the foundation for plant tissue culture.

Introduction: In a plant body, tissues do not work alone but are organised into larger groups called tissue systems.
Key Points:
1. Dermal tissue system — Forms the outer covering of the plant, protecting inner parts and reducing water loss.
2. Ground tissue system — Forms the main body of the plant between the dermal and conducting tissues; includes parenchyma, collenchyma and sclerenchyma.
3. Vascular tissue system — Consists of conducting tissues xylem and phloem, transporting water, minerals and food throughout the plant.
Conclusion: The three tissue systems work together to ensure protection, support and transport in the plant body.

Introduction: Yoga, described in ancient Indian texts, includes physical postures, breathing and meditation that benefit the musculoskeletal system.
Key Points:
1. Improves flexibility and posture — Yoga postures and regular exercise keep bones strong, muscles fit and joints flexible.
2. Prevents lifestyle diseases — Research shows yoga reduces stress and helps prevent lifestyle diseases; June 21 is observed as International Yoga Day.
3. Nutrition and maintenance — Proper nutrition, regular exercise and correct posture protect the body from stiffness and maintain bone and muscle health.
Conclusion: Maintaining correct posture, proper nutrition, regular exercise and yoga keeps the musculoskeletal system healthy and functional.

(a) Collenchyma tissue is responsible for this flexibility.
(b) Pectin deposited at the corners of the cells gives collenchyma its flexibility.
(c) The stem would become rigid and brittle and would likely break in strong wind.
(d) The tendrils of climbers, which need to bend around supports, also rely on this flexible tissue.

(a) The tree loses protection from water loss, injury and parasites.
(b) The vascular tissue, including phloem and cambium, lies beneath the bark and would be affected.
(c) Transport of food from the leaves to the roots through the phloem would be hampered.
(d) The answers assume a standard dicot stem structure with bark, cambium, phloem and xylem arranged in that order.

(a) Type B cuttings contained nodes with intercalary meristem that could regenerate into a new plant.
(b) Type B cuttings had nodes, whereas type A cuttings did not.
(c) Whether new shoots or sprouts appeared was the observation that determined growth.
(d) The same soil, water, sunlight, temperature and cutting size should be kept constant for a fair comparison.

(a) Sclerenchyma tissue provides this strength.
(b) Sclerenchyma has thick walls due to lignin deposition, making the cells hard and strong.
(c) Parenchyma has thin walls and is designed for storage, so it cannot provide mechanical strength.
(d) Walnut shells, seed coats and the veins of leaves also contain sclerenchyma for hardness.

(a) Nervous tissue, made of neurons, carries messages from the brain to the heart.
(b) Muscles need more oxygen to release energy, so breathing becomes faster to take in more oxygen.
(c) Increased blood flow to the skin makes the face appear red.
(d) Cardiac muscle tissue enables the heart to beat rhythmically.

(a) The lateral meristem (cambium) is responsible for the increase in girth.
(b) It is located in a ring along the circumference of the stem.
(c) Wide rings indicate favourable growing conditions, while narrow rings indicate unfavourable conditions.
(d) Scientists estimate the age of a tree by counting the number of annual rings.

(a) Haemoglobin present in red blood cells gives blood its red colour.
(b) Red blood oozes out, and platelets help form a clot that stops the bleeding.
(c) White blood cells collect at the infected area, causing inflammation, redness and sometimes pus.
(d) Blood is a connective tissue, and its fluid part is called plasma, which makes up about 55% of blood volume.

(a) Nervous tissue, made of neurons, enables this quick response.
(b) The three main parts of a neuron are the cell body, dendrites and axon.
(c) The brain sends signals through neurons to the muscles, instructing them to contract.
(d) No — muscles receive instructions from nervous tissue; for example, during exercise the brain signals the heart to beat faster.

(a) Crown gall disease is caused by the bacterium Agrobacterium tumefaciens.
(b) Yes — the disease produces tumour-like swellings on stems due to rapid, uncontrolled cell division.
(c) Scientists studied how the bacterium transfers genes into plant cells and used this mechanism to their advantage.
(d) Agrobacterium is now used as a tool to introduce useful genes into plants, producing improved and disease-resistant crop varieties.

(a) Rohan's statement is true for simple tissues but not fully for complex tissues.
(b) Simple tissues are made of one type of cell, while complex tissues are made of more than one type of cell working together.
(c) Parenchyma, collenchyma or sclerenchyma are examples of simple tissues.
(d) Xylem is a complex tissue made of tracheids, vessels, xylem parenchyma and xylem fibres; phloem is made of sieve tubes, companion cells, phloem parenchyma and phloem fibres.

Introduction: Plant tissues are classified based on their ability to divide — meristematic tissues divide actively, while permanent tissues are specialised.
Key Points:
1. Meristematic types — Apical (root/shoot tips, length), lateral (stem circumference, girth) and intercalary (base of internodes, regeneration) meristems.
2. Meristematic cell features — Small, thin walls, dense cytoplasm, prominent nucleus, no vacuoles, tightly packed for rapid division.
3. Simple permanent tissues — Parenchyma (thin walls, storage), collenchyma (unevenly thickened, flexibility), sclerenchyma (lignified, dead, strength).
4. Complex permanent tissues — Xylem (water and minerals, tracheids/vessels/parenchyma/fibres) and phloem (food, sieve tubes/companion cells/parenchyma/fibres).
5. Differentiation — Meristematic cells lose the ability to divide and become specialised permanent tissues through differentiation.
Conclusion: The transition from meristematic to permanent tissues through differentiation enables plants to grow and specialise for diverse functions.

Introduction: Animal tissues are groups of specialised cells that perform specific functions, adapted to the animal's mobile and heterotrophic way of life.
Key Points:
1. Epithelial tissue — Closely packed cells forming the outer covering (skin) and lining internal organs; functions include protection, exchange, secretion and absorption.
2. Connective tissue — Connects and supports organs; includes blood (fluid, plasma), bone (rigid matrix), cartilage (soft matrix), tendons and ligaments.
3. Muscular tissue — Skeletal (voluntary, striated), smooth (involuntary, in stomach/intestines), and cardiac (involuntary, heart, tireless).
4. Nervous tissue — Neurons with cell body, dendrites and axon; receives, processes and transmits messages for control and coordination.
5. Coordination — Muscles cannot function independently; they receive instructions from nervous tissue, with the brain as the control centre.
Conclusion: The four animal tissue types work together to enable movement, support, communication and protection in the body.

Introduction: Xylem and phloem are complex permanent tissues that together form the vascular tissue system, transporting materials throughout the plant.
Key Points:
1. Xylem components — Tracheids, vessels, xylem parenchyma (only living part) and xylem fibres; tubular, thick-walled, mostly dead.
2. Xylem function — Transports water and minerals from roots to all parts of the plant and provides mechanical strength.
3. Phloem components — Sieve tubes, companion cells, phloem parenchyma and phloem fibres; mostly living cells joined end to end.
4. Phloem function — Sieve tubes transport food from leaves to other parts; companion cells regulate sieve tube functions and monitor sugar loading/unloading.
5. Storage and support — Phloem parenchyma stores food, resin, tannins and latex; phloem fibres provide strength to the sieve tubes.
Conclusion: Xylem and phloem together ensure that water, minerals and food are efficiently transported to all parts of the plant.

Introduction: Muscular tissue produces voluntary and involuntary movements, with three distinct types adapted for different functions.
Key Points:
1. Skeletal muscles — Voluntary; attached to skeleton; bundles of long cylindrical, unbranched, multinucleate, striated fibres; enable running, writing, lifting.
2. Smooth muscles — Involuntary; spindle-shaped, single nucleus, non-striated; found in stomach, intestines; enable slow, continuous movements like digestion.
3. Cardiac muscles — Involuntary; found only in the heart; cylindrical, branched, single nucleus, faint striations; work tirelessly and rhythmically without fatigue.
4. Control by nervous tissue — All muscles receive instructions from the nervous system; the brain signals the heart to beat faster during exercise.
5. Functional significance — Voluntary muscles allow conscious movement, involuntary muscles handle automatic processes, and cardiac muscle keeps the heart beating for life.
Conclusion: Each muscle type is structurally specialised to match its specific role — voluntary movement, digestion or the ceaseless beating of the heart.

Introduction: The musculoskeletal system, made of bones, muscles, joints, cartilage, tendons and ligaments, enables movement and provides support.
Key Points:
1. Bones and skeleton — The adult skeleton makes up about 12–15% of body weight; the skull protects the brain, and the vertebral column supports the body.
2. Tendons and ligaments — Tendons connect muscles to bones and transmit force for movement; ligaments connect bone to bone and prevent dislocation.
3. Joint types — Ball and socket (shoulder, multi-directional), hinge (elbow, one direction), pivot (skull-backbone, rotation), and fixed (skull, immovable).
4. Cartilage — Soft, jelly-like matrix providing flexibility and cushioning; found between vertebrae, in ears and nose, and at bone ends for shock absorption.
5. Nervous control — The entire system functions under the control of the nervous system; muscles pull on bones via tendons to produce movement at joints.
Conclusion: The coordinated action of bones, muscles and joints under nervous control enables all body movements while protecting vital organs.

Introduction: Plants have specialised protective and supporting tissues that help them survive in their fixed, often harsh environments.
Key Points:
1. Epidermis and cuticle — The outermost layer of tightly packed cells covered with a waxy cuticle of cutin; reduces water loss and protects from injury and parasites.
2. Stomata and root hair — Stomata in leaves allow gaseous exchange and transpiration; root hair increases surface area for water and mineral absorption.
3. Parenchyma — Living cells with thin walls and intercellular spaces; stores food, performs photosynthesis in green parts, and forms air spaces in aquatic plants.
4. Collenchyma — Living cells with unevenly thickened corners due to pectin; provides support and flexibility, allowing stems and tendrils to bend without breaking.
5. Sclerenchyma — Dead cells with thick lignified walls; provides hardness and strength; found in stems, leaf veins, and hard coverings of seeds and nuts.
Conclusion: Protective and supporting tissues enable plants to survive environmental stresses, maintain their structure and perform essential functions.

Introduction: Blood is a fluid connective tissue that connects different parts of the body by transporting nutrients, gases, hormones and waste.
Key Points:
1. Plasma — The fluid part constituting about 55% of blood volume; carries dissolved nutrients, hormones and waste throughout the body.
2. Red Blood Cells — Contain haemoglobin (iron-rich protein) giving blood its red colour; transport oxygen to all cells; live about 4 months and are replaced regularly.
3. White Blood Cells — Collect at infected areas, causing inflammation, redness, swelling and possible pus formation; defend the body against infection.
4. Platelets — Help in blood clotting at the site of injury, preventing excessive blood loss and enabling healing.
5. Exercise response — During exercise, muscles need more oxygen, so breathing becomes faster and blood flow increases, causing the face to appear red.
Conclusion: Blood's components work together to transport materials, fight infection, and prevent blood loss, connecting and sustaining all body systems.

Introduction: Nervous tissue forms the body's control and coordination network, with neurons as its specialised cells for receiving and transmitting messages.
Key Points:
1. Cell body — Contains the nucleus and controls all cell activities; serves as the neuron's command centre.
2. Dendrites — Branch-like structures that receive signals from other neurons and convey them to the cell body.
3. Axon — A long fibre that carries messages away from the cell body, ending at axon terminals that transmit messages to other cells, muscles or glands.
4. Brain as control centre — The brain coordinates activities, memory and responses; it signals the heart to beat faster during exercise to meet oxygen demand.
5. Muscle dependence — Muscles, both voluntary and involuntary, cannot function independently; they receive instructions from nervous tissue.
Conclusion: Neurons form a rapid communication network that enables the body to sense, respond and coordinate all its activities efficiently.

Introduction: Plant and animal tissues differ in structure and function because plants and animals have fundamentally different ways of life.
Key Points:
1. Movement and support — Plants are fixed and need rigid cell walls for support; animals move and need flexible cells without cell walls.
2. Nutrition — Plants have tissues for photosynthesis (chloroplasts in green parts); animals have tissues for digesting food from external sources.
3. Growth pattern — Plant growth is localised in meristems (tips, circumference, nodes); animal growth is more distributed throughout the body.
4. Transport tissues — Plants have xylem and phloem for water, minerals and food; animals have blood as a fluid connective tissue for transport.
5. Response to environment — Animals have nervous tissue for rapid responses; plants respond more slowly through growth and hormonal changes.
Conclusion: The structural and functional differences between plant and animal tissues reflect their distinct lifestyles — stationary autotrophic plants versus mobile heterotrophic animals.

Introduction: As plants grow older, new protective layers form, and the study of plant diseases can lead to valuable scientific tools.
Key Points:
1. Cork cambium formation — In older plants, cells below the epidermis develop the ability to divide, acting as lateral meristematic cells and forming the cork cambium.
2. Cork cells — The cork cambium produces cork cells that are dead, compactly arranged and contain a substance making them impermeable to water and gases, forming the bark.
3. Bark protection — The bark protects the tree from injury, water loss and pathogens, replacing the single-layered epidermis of young plants.
4. Crown gall disease — Caused by Agrobacterium tumefaciens, it produces tumour-like swellings from uncontrolled cell division in plant stems.
5. Turning disease to advantage — Scientists studied how the bacterium transfers genes into plant cells and now use Agrobacterium as a tool to introduce useful genes for improved crops.
Conclusion: Understanding plant protective tissues and disease mechanisms has both explained natural processes and enabled powerful tools for crop improvement.