CBSE Important Questions Class 11 Biology Chapter 13: Plant Growth And Development With Answers

Plant growth is an irreversible permanent increase in the size of a cell, organ, or whole plant.
Plant development includes growth, differentiation, maturation, senescence, and responses to internal and external factors.

A seed becomes a mature plant through a precise sequence of growth, differentiation, and development. CBSE 2026 tests CBSE Important Questions Class 11 Biology Chapter 13 through meristems, growth phases, growth rates, developmental plasticity, and plant growth regulators. The NCERT Reprint 2026-27 covers auxins, gibberellins, cytokinins, ethylene, abscisic acid, and their agricultural uses. Students must also practise NCERT exercise patterns on PGR applications, stress responses, apical dominance, and growth curves.

Key Takeaways

• Growth Definition: Growth is an irreversible permanent increase in size.
• Growth Measurement: Plant growth can be measured by length, area, volume, weight, or cell number.
• PGR Groups: Auxins, gibberellins, and cytokinins promote growth in many plant processes.
• ABA Rule: Abscisic acid acts as a stress hormone and inhibits seed germination.

CBSE Important Questions Class 11 Biology Chapter 13 Structure 2026

CBSE Important Questions Class 11 Biology Chapter 13: Key Concepts

These class 11 biology chapter 13 important questions focus on NCERT definitions and process links. Learn growth, differentiation, development, and PGR roles before practising application questions.

Q1. What Is Plant Growth?

Plant growth is an irreversible permanent increase in the size of a cell, organ, or whole plant. It uses metabolic energy.

1. Given Data:
   Growth involves permanent increase in size.
2. Key Features:
   It may occur in cell number, length, area, volume, or weight.
3. Final Result:
   Growth is irreversible and permanent

Q2. What Is Plant Development?

Plant development includes all changes from seed germination to senescence. It includes growth and differentiation.

1. Given Data:
   Development covers the whole plant life cycle.
2. Formula-Like Rule:
   Development = growth + differentiation
3. Final Result:
   Development includes growth, differentiation, maturation, and senescence

Q3. Why Is Plant Growth Called Indeterminate?

Plant growth is indeterminate because meristems keep adding new cells throughout plant life. This creates open growth.

1. Given Data:
   Meristems retain division capacity.
2. Examples:
   Root apical meristem and shoot apical meristem.
3. Final Result:
   Plants show unlimited growth due to meristems

Q4. What Is Open Form Of Growth?

Open form of growth means new cells keep adding to the plant body through meristem activity. Plants show this throughout life.

1. Given Data:
   Meristematic cells divide continuously.
2. Effect:
   New cells later differentiate into plant tissues.
3. Final Result:
   Open growth depends on meristem activity

Plant Growth And Development Class 11 MCQ With Answers

These plant growth and development class 11 important questions test definitions, growth phases, PGRs, and NCERT facts. Each MCQ follows CBSE 2026 style.

Q1. Growth In Plants Is Best Defined As Which Process?

Growth is an irreversible permanent increase in size. It can occur in a cell, organ, or whole plant.

1. Options:
   (A) Temporary increase in size
   (B) Irreversible permanent increase in size
   (C) Only increase in dry weight
   (D) Only increase in cell number
2. Rule Used:
   NCERT defines growth as irreversible and permanent.
3. Final Result:
   Answer: (B) Irreversible permanent increase in size

Q2. Which Tissue Allows Unlimited Growth In Plants?

Meristematic tissue allows unlimited growth in plants. Its cells divide and self-perpetuate.

1. Options:
   (A) Xylem
   (B) Phloem
   (C) Meristem
   (D) Epidermis
2. Rule Used:
   Meristems retain division capacity.
3. Final Result:
   Answer: (C) Meristem

Q3. Which Phase Has Cells Rich In Protoplasm And Large Nuclei?

Meristematic phase has cells rich in protoplasm and large conspicuous nuclei.

1. Options:
   (A) Maturation phase
   (B) Elongation phase
   (C) Meristematic phase
   (D) Senescence phase
2. Rule Used:
   Dividing cells show dense protoplasm.
3. Final Result:
   Answer: (C) Meristematic phase

Q4. Which Growth Curve Is Typical Of Living Organisms In Natural Conditions?

Sigmoid growth curve is typical of living organisms in natural conditions. It shows lag, log, and stationary phases.

1. Options:
   (A) Straight line
   (B) Sigmoid curve
   (C) Circular curve
   (D) Random curve
2. Rule Used:
   Geometric growth produces an S-shaped curve.
3. Final Result:
   Answer: (B) Sigmoid curve

Q5. Which PGR Is Called The Stress Hormone?

Abscisic acid is called the stress hormone. It increases tolerance to stress and closes stomata.

1. Options:
   (A) Auxin
   (B) Cytokinin
   (C) ABA
   (D) Gibberellin
2. Rule Used:
   ABA controls stress responses.
3. Final Result:
   Answer: (C) ABA

Q6. Which PGR Is A Simple Gas?

Ethylene is a simple gaseous plant growth regulator. It promotes fruit ripening and senescence.

1. Options:
   (A) Auxin
   (B) Ethylene
   (C) Gibberellin
   (D) Cytokinin
2. Rule Used:
   Ethylene is gaseous.
3. Final Result:
   Answer: (B) Ethylene

Q7. Which PGR Helps In Rooting Of Stem Cuttings?

Auxin helps initiate rooting in stem cuttings. It is widely used in plant propagation.

1. Options:
   (A) Auxin
   (B) ABA
   (C) Ethylene
   (D) Kinetin
2. Rule Used:
   Auxins initiate rooting.
3. Final Result:
   Answer: (A) Auxin

Q8. Which PGR Delays Leaf Senescence?

Cytokinin delays leaf senescence by promoting nutrient mobilisation. It also supports cell division.

1. Options:
   (A) ABA
   (B) Cytokinin
   (C) Ethylene
   (D) 2,4-D
2. Rule Used:
   Cytokinins delay senescence.
3. Final Result:
   Answer: (B) Cytokinin

Growth In Plants Class 11 Important Questions

These growth in plants class 11 questions cover growth measurement, phases, and conditions. NCERT uses root tips, leaves, pollen tubes, and fruits as examples.

Q1. Why Is One Parameter Not Enough To Measure Growth In Plants?

One parameter is not enough because different plant parts show growth differently. Growth may appear as length, area, volume, weight, or cell number.

1. Given Data:
   Plant organs grow in different ways.
2. Examples:
   Pollen tube growth uses length.
   Leaf growth uses surface area.
   Watermelon cell growth uses cell size.
3. Final Result:
   Growth needs different measurable parameters

Q2. What Are The Main Parameters Used To Measure Growth?

Growth is measured through fresh weight, dry weight, length, area, volume, and cell number. The chosen parameter depends on the organ.

1. Length:
   Used for roots and pollen tubes.
2. Area:
   Used for dorsiventral leaves.
3. Weight:
   Used for whole organs or seedlings.
4. Final Result:
   Growth can be measured through multiple parameters

Q3. What Are The Three Phases Of Growth?

The three phases are meristematic phase, elongation phase, and maturation phase. They occur clearly near root and shoot tips.

1. Meristematic Phase:
   Cells divide actively.
2. Elongation Phase:
   Cells enlarge and vacuolate.
3. Maturation Phase:
   Cells attain final size and function.
4. Final Result:
   Growth has meristematic, elongation, and maturation phases

Q4. What Happens In The Meristematic Phase Of Growth?

Cells in the meristematic phase divide actively. They have dense protoplasm, large nuclei, and thin primary walls.

1. Location:
   Root apex and shoot apex.
2. Cell Features:
   Thin walls, large nuclei, abundant plasmodesmata.
3. Final Result:
   Meristematic cells actively divide

Q5. What Happens In The Elongation Phase Of Growth?

Cells in the elongation phase increase in size. They show vacuolation, enlargement, and new cell wall deposition.

1. Location:
   Just behind the meristematic zone.
2. Key Features:
   Cell enlargement and vacuole formation.
3. Final Result:
   Elongation phase increases cell size

Q6. What Happens In The Maturation Phase Of Growth?

Cells in the maturation phase attain maximum size and specialised structure. They undergo wall thickening and protoplasmic changes.

1. Location:
   Away from the root or shoot apex.
2. Key Features:
   Wall thickening and functional maturity.
3. Final Result:
   Maturation phase produces specialised cells

Arithmetic Growth And Geometric Growth Class 11 Questions

These arithmetic growth and geometric growth class 11 questions explain growth rates. CBSE 2026 can ask formulas, curves, and phase differences.

Q1. What Is Arithmetic Growth?

Arithmetic growth occurs when only one daughter cell continues to divide after mitosis. The other cell differentiates and matures.

1. Given Data:
   One daughter cell keeps dividing.
2. Example:
   Root elongating at a constant rate.
3. Formula Used:
   Lt = L0 + rt
4. Final Result:
   Arithmetic growth gives a linear curve

Q2. What Is The Formula For Arithmetic Growth?

The formula is Lt = L0 + rt. It shows length increase at a constant rate.

1. Given Data:
   Lt = length at time t
   L0 = length at time zero
   r = growth rate
   t = time
2. Formula Used:
   Lt = L0 + rt
3. Final Result:
   Lt = L0 + rt

Q3. What Is Geometric Growth?

Geometric growth occurs when both daughter cells retain division ability. It produces lag, exponential, and stationary phases.

1. Given Data:
   Both progeny cells divide.
2. Growth Pattern:
   Slow start, rapid increase, then stationary phase.
3. Final Result:
   Geometric growth produces a sigmoid curve

Q4. What Is The Formula For Exponential Growth?

The formula is W1 = W0ert. It expresses final size after exponential growth.

1. Given Data:
   W1 = final size
   W0 = initial size
   r = growth rate
   t = time
   e = base of natural logarithms
2. Formula Used:
   W1 = W0ert
3. Final Result:
   W1 = W0ert

Q5. What Is A Sigmoid Growth Curve Class 11?

A sigmoid growth curve is an S-shaped curve showing lag, log, and stationary phases. It is typical of living organisms.

1. Lag Phase:
   Growth starts slowly.
2. Log Phase:
   Growth increases rapidly.
3. Stationary Phase:
   Growth slows due to limited nutrients.
4. Final Result:
   Sigmoid curve shows natural growth pattern

Q6. What Is Absolute Growth Rate?

Absolute growth rate is total growth per unit time. It compares actual increase in size.

1. Given Data:
   Total growth over time.
2. Formula Idea:
   Absolute growth = total increase/time
3. Final Result:
   Absolute growth rate measures actual growth increase

Q7. What Is Relative Growth Rate?

Relative growth rate is growth per unit time expressed on a common initial basis. It compares growth efficiency.

1. Given Data:
   Growth relative to initial size.
2. Use:
   Compare differently sized organs.
3. Final Result:
   Relative growth rate compares growth efficiency

Differentiation Dedifferentiation Redifferentiation Class 11 Questions

These differentiation dedifferentiation redifferentiation class 11 questions test NCERT definitions and examples. They explain how plant cells gain, regain, and lose division capacity.

Q1. What Is Differentiation In Plants?

Differentiation is the maturation of cells to perform specific functions. Cells develop structural changes in walls and protoplasm.

1. Given Data:
   Cells arise from meristems.
2. Example:
   Tracheary elements lose protoplasm and develop lignified walls.
3. Final Result:
   Differentiation produces specialised cells

Q2. What Is Dedifferentiation In Plants?

Dedifferentiation occurs when living differentiated cells regain the capacity to divide. It forms new meristematic tissues.

1. Given Data:
   Differentiated cells regain division ability.
2. Examples:
   Interfascicular cambium and cork cambium.
3. Final Result:
   Dedifferentiation restores cell division capacity

Q3. What Is Redifferentiation In Plants?

Redifferentiation occurs when dedifferentiated cells again lose division capacity and mature into specialised cells.

1. Given Data:
   Dedifferentiated cells divide.
2. Later Change:
   New cells mature and perform specific functions.
3. Final Result:
   Redifferentiation forms mature specialised tissues

Q4. Why Is Differentiation In Plants Called Open?

Differentiation is open because cells from the same meristem can form different mature structures. Their final role depends on position.

1. Given Data:
   Same meristem produces different cell types.
2. Example:
   Cells near root apex form root cap or epidermis by position.
3. Final Result:
   Plant differentiation depends on cell position

Q5. How Does A Tracheary Element Show Differentiation?

A tracheary element shows differentiation by losing protoplasm and forming lignocellulosic secondary walls. It transports water under tension.

1. Cell Change:
   Protoplasm is lost.
2. Wall Change:
   Strong secondary wall forms.
3. Final Result:
   Tracheary elements specialise for water transport

Development In Plants Class 11 Important Questions

These plant development class 11 questions cover life-cycle changes and plasticity. Development includes every change from germination to senescence.

Q1. What Is Development In Plants?

Development includes all changes in a plant from seed germination to senescence. It combines growth and differentiation.

1. Given Data:
   Development covers the whole life cycle.
2. Formula-Like Rule:
   Development = growth + differentiation
3. Final Result:
   Development includes growth, differentiation, and senescence

Q2. What Is Plasticity In Plant Development?

Plasticity is the ability of plants to follow different developmental pathways under different conditions. Heterophylly shows plasticity.

1. Given Data:
   Plants respond to environment or life phase.
2. Examples:
   Cotton, coriander, larkspur, and buttercup.
3. Final Result:
   Plasticity allows different structures under different conditions

Q3. What Is Heterophylly?

Heterophylly is the production of different leaf shapes on the same plant. It can depend on plant age or environment.

1. Developmental Example:
   Juvenile and mature leaves differ.
2. Environmental Example:
   Buttercup leaves differ in air and water.
3. Final Result:
   Heterophylly is an example of plasticity

Q4. What Factors Control Plant Development?

Plant development is controlled by intrinsic and extrinsic factors. These include genes, PGRs, light, temperature, water, oxygen, and nutrition.

1. Intrinsic Factors:
   Genetic factors and plant growth regulators.
2. Extrinsic Factors:
   Light, temperature, water, oxygen, nutrition, and gravity.
3. Final Result:
   Plant development depends on internal and external controls

Plant Growth Regulators Class 11 Important Questions

These plant growth regulators class 11 questions cover PGR groups, discovery, functions, and applications. NCERT focuses on five major PGR categories.

Q1. What Are Plant Growth Regulators?

Plant growth regulators are small simple molecules that control growth and development. They include auxins, gibberellins, cytokinins, ethylene, and ABA.

1. Chemical Nature:
   They may be indole compounds, adenine derivatives, gases, terpenes, or carotenoid derivatives.
2. Function:
   They regulate growth, dormancy, flowering, fruiting, and stress responses.
3. Final Result:
   PGRs control plant growth and development

Q2. What Are Plant Growth Promoters?

Plant growth promoters are PGRs that support cell division, cell enlargement, flowering, fruiting, and seed formation.

1. Examples:
   Auxins, gibberellins, and cytokinins.
2. Main Roles:
   Growth promotion and pattern formation.
3. Final Result:
   Auxins, gibberellins, and cytokinins act as growth promoters

Q3. Which PGRs Mainly Inhibit Growth?

Abscisic acid mainly inhibits growth and promotes dormancy. Ethylene also acts largely as a growth inhibitor.

1. ABA Role:
   Dormancy, stomatal closure, stress tolerance.
2. Ethylene Role:
   Senescence, abscission, fruit ripening.
3. Final Result:
   ABA is a major growth inhibitor

Q4. How Were Auxins Discovered?

Auxins were linked to phototropism through Darwin’s coleoptile experiments. F.W. Went later isolated auxin from oat coleoptile tips.

1. Observation:
   Coleoptiles bend towards light.
2. Conclusion:
   The tip produces a transmittable influence.
3. Final Result:
   Auxin controls phototropic bending

Q5. How Were Gibberellins Discovered?

Gibberellins were discovered through bakanae disease in rice seedlings. The fungus Gibberella fujikuroi caused abnormal elongation.

1. Scientist:
   E. Kurosawa reported the effect in 1926.
2. Active Substance:
   Later identified as gibberellic acid.
3. Final Result:
   Gibberellins were discovered from rice seedling disease studies

Auxins Gibberellins Cytokinins Ethylene And ABA Class 11 Questions

These auxins class 11 biology and gibberellins class 11 biology questions focus on physiological effects. CBSE 2026 often asks application-based PGR questions.

Q1. What Are The Main Functions Of Auxins?

Auxins initiate rooting, promote flowering in pineapple, induce parthenocarpy, and control apical dominance.

1. Natural Auxins:
   IAA and IBA.
2. Synthetic Auxins:
   NAA and 2,4-D.
3. Applications:
   Rooting in cuttings and weed control.
4. Final Result:
   Auxins promote rooting and control apical dominance

Q2. What Is Apical Dominance?

Apical dominance is the inhibition of lateral bud growth by the growing apical bud. Auxin controls this process.

1. Given Data:
   Apical bud suppresses axillary buds.
2. Application:
   Decapitation promotes lateral branching.
3. Final Result:
   Apical dominance controls branch growth

Q3. What Are The Main Functions Of Gibberellins?

Gibberellins increase stem length, improve fruit shape, delay senescence, and promote bolting. GA3 is the most studied form.

1. Applications:
   Grape stalk elongation and apple shape improvement.
2. Crop Use:
   Sugarcane stem length increases.
3. Final Result:
   Gibberellins promote elongation and bolting

Q4. What Are The Main Functions Of Cytokinins?

Cytokinins promote cytokinesis, new leaf formation, lateral shoot growth, and nutrient mobilisation. They delay leaf senescence.

1. Natural Cytokinin:
   Zeatin occurs in corn kernels and coconut milk.
2. Major Function:
   Cell division promotion.
3. Final Result:
   Cytokinins promote cell division and delay senescence

Q5. What Are The Main Functions Of Ethylene?

Ethylene promotes fruit ripening, senescence, abscission, and respiratory climacteric. It also breaks seed and bud dormancy.

1. Nature:
   Ethylene is a gaseous PGR.
2. Agricultural Source:
   Ethephon releases ethylene slowly.
3. Final Result:
   Ethylene promotes fruit ripening

Q6. What Are The Main Functions Of Abscisic Acid?

Abscisic acid inhibits growth, closes stomata, promotes dormancy, and increases stress tolerance. It acts against gibberellins in many cases.

1. Main Role:
   Growth inhibition and stress response.
2. Seed Role:
   It supports seed maturation and dormancy.
3. Final Result:
   ABA is called the stress hormone

Plant Growth And Development Class 11 NCERT Questions

These plant growth and development class 11 NCERT questions follow the exercise patterns. Each answer stays within NCERT Reprint 2026-27.

Q1. Define Growth, Differentiation, Development, Dedifferentiation, Redifferentiation, Determinate Growth, Meristem, And Growth Rate.

These terms describe plant body formation and functional maturity. Each term has a specific NCERT meaning.

1. Growth:
   Irreversible permanent increase in size.
2. Differentiation:
   Maturation of cells for specific functions.
3. Development:
   All changes from germination to senescence.
4. Dedifferentiation:
   Mature cells regain division capacity.
5. Redifferentiation:
   Dividing cells mature again for specific functions.
6. Determinate Growth:
   Growth that stops after a point.
7. Meristem:
   Tissue with cells that divide continuously.
8. Growth Rate:
   Increase in growth per unit time.
9. Final Result:
   These terms explain plant growth and development stages

Q2. Why Are Growth And Differentiation In Higher Plants Called Open?

Growth and differentiation are open because plants keep producing new cells and structures through meristems. Cell fate depends on position.

1. Open Growth:
   Meristems keep adding cells.
2. Open Differentiation:
   Cells from the same meristem mature differently.
3. Final Result:
   Higher plants show open growth and open differentiation

Q3. Which PGR Would You Use To Induce Rooting In A Twig?

Use auxin to induce rooting in a twig. Auxins initiate roots in stem cuttings.

1. Given Task:
   Rooting in twig.
2. PGR Used:
   Auxin such as IAA, IBA, or NAA.
3. Final Result:
   Auxin induces rooting

Q4. Which PGR Would You Use To Quickly Ripen A Fruit?

Use ethylene to quickly ripen a fruit. Ethephon is commonly used as an ethylene source.

1. Given Task:
   Fruit ripening.
2. PGR Used:
   Ethylene.
3. Final Result:
   Ethylene hastens fruit ripening

Q5. Which PGR Would You Use To Delay Leaf Senescence?

Use cytokinin to delay leaf senescence. Cytokinins promote nutrient mobilisation.

1. Given Task:
   Delay leaf ageing.
2. PGR Used:
   Cytokinin.
3. Final Result:
   Cytokinin delays leaf senescence

Q6. Which PGR Would You Use To Induce Growth In Axillary Buds?

Use cytokinin to induce growth in axillary buds. Cytokinins overcome apical dominance.

1. Given Task:
   Axillary bud growth.
2. PGR Used:
   Cytokinin.
3. Final Result:
   Cytokinin promotes axillary bud growth

Q7. Which PGR Would You Use To Bolt A Rosette Plant?

Use gibberellin to bolt a rosette plant. Gibberellins promote internode elongation before flowering.

1. Given Task:
   Bolting in rosette plants.
2. PGR Used:
   Gibberellin.
3. Final Result:
   Gibberellin induces bolting

Q8. Which PGR Would You Use To Induce Immediate Stomatal Closure?

Use abscisic acid to induce stomatal closure. ABA increases plant tolerance to water stress.

1. Given Task:
   Stomatal closure.
2. PGR Used:
   ABA.
3. Final Result:
   ABA induces stomatal closure

Q9. What Happens If GA3 Is Applied To Rice Seedlings?

Rice seedlings show elongated growth after GA3 application. Gibberellins promote axis elongation.

1. Given Data:
   GA3 is applied to rice seedlings.
2. Effect:
   Stem elongation increases.
3. Final Result:
   GA3 causes seedling elongation

Q10. What Happens If A Rotten Fruit Gets Mixed With Unripe Fruits?

The unripe fruits ripen faster because rotten fruits release ethylene. Ethylene promotes fruit ripening.

1. Given Data:
   Rotten fruit releases ethylene.
2. Effect:
   Ethylene reaches unripe fruits.
3. Final Result:
   Unripe fruits ripen faster

Plant Growth And Development Class 11 Previous Year Questions

These plant growth and development class 11 previous year questions cover repeated board-style concepts. They focus on growth curves, PGR effects, and NCERT definitions.

Q1. Why Is Abscisic Acid Called Stress Hormone?

Abscisic acid is called stress hormone because it increases plant tolerance to stress. It also causes stomatal closure.

1. Stress Role:
   ABA helps plants tolerate unfavourable conditions.
2. Stomatal Role:
   ABA closes stomata during water stress.
3. Final Result:
   ABA is the stress hormone

Q2. Why Does A Defoliated Plant Not Respond Properly To Photoperiodic Cycle?

A defoliated plant may not respond properly because leaves perceive photoperiodic stimulus. The flowering signal moves from leaves.

1. Given Data:
   Leaves detect light duration.
2. Effect:
   Removing leaves reduces photoperiod response.
3. Final Result:
   Leaves are required for photoperiodic response

Q3. What Happens If Dividing Cells Stop Differentiating?

If dividing cells stop differentiating, they form undifferentiated masses of cells. Such growth can resemble callus-like tissue.

1. Given Data:
   Cell division continues.
2. Missing Process:
   Differentiation stops.
3. Final Result:
   Cells fail to form specialised tissues

Q4. What Happens If Cytokinin Is Not Added To Culture Medium?

Callus growth may reduce because cytokinin promotes cell division. It supports shoot formation and tissue culture growth.

1. Given Data:
   Culture medium lacks cytokinin.
2. Effect:
   Cell division and shoot formation decline.
3. Final Result:
   Cytokinin supports tissue culture growth

Q5. Why Is Water Essential For Plant Growth?

Water is essential because it supports cell enlargement, turgidity, and enzymatic activity. It also provides a medium for metabolism.

1. Growth Role:
   Cells enlarge through water uptake.
2. Metabolic Role:
   Enzymes need an aqueous medium.
3. Final Result:
   Water supports extension growth

Q6. Why Is Oxygen Required For Plant Growth?

Oxygen is required because it releases metabolic energy needed for growth activities. Respiration depends on oxygen.

1. Given Data:
   Growth needs energy.
2. Process:
   Oxygen supports aerobic respiration.
3. Final Result:
   Oxygen provides energy for growth