Plant Growth and Development Class 11 Notes PDF | NEET Biology Chapter 15 | PGR Hormones

Hello Friends 👋

As a NEET Dropper, I'm sharing my complete notes of Chapter 15: Plant Growth and Development with you all.

Sigmoid Curve se leke 5 PGR tak - Full NCERT + PYQ + Google se Hatke Tricks! 

2-3 Questions fix aate hain NEET me is chapter se 🔥

Jo coaching me bhi nahi milta wo yaha hai =

Auxin ka Avena Test + GA ka Bakane Disease + Cytokinin ka Richmond-Lang + Ethylene Triple Response + ABA Stress Hormone

Hope it helps you crack NEET 2027! 📚

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#NEET2027 #NEETDropper #PlantGrowthAndDevelopment #Auxin #Gibberellin #Cytokinin #Ethylene #ABA #Photoperiodism #Vernalization #NCERTBiology #BiologyNotes

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### *1. GROWTH KYA HAI* `Definition Line`

Definition = Irreversible Permanent Increase in Size, Volume, Weight, Dry Mass

Features = Measurable + Quantitative + Accompanied by Metabolism

Plant Growth = Indeterminate = Due to Meristems = Apical, Intercalary, Lateral

Open Growth = New Cells Added Throughout Life = Leaves, Flowers, Fruits Determinate

*Figure 1: Growth Curve*

Sigmoid Curve = S-shaped = 3 Phases

1. Lag Phase = Slow = New Environment Adaptation

2. Log/Exponential = Rapid = Max Growth Rate = Daughter Cells Divide

3. Stationary = Constant = Nutrients Limit + Senescence

Equation: Lt = L0 + rt = Arithmetic, W1 = W0 × e^rt = Geometric

### *2. GROWTH RATES* `NEET Numerical**

A. Arithmetic Growth = Root Elongation = Constant Rate

   Example: One Daughter Cell Divide, One Remain Meristematic

   Curve = Linear, Equation: Lt = L0 + rt

   Plot: Length vs Time = Straight Line

B. Geometric Growth = All Cells Divide = Embryo, Cell Division

   Equation: W1 = W0 × e^rt

   r = Relative Growth Rate = Efficiency Index = W1-W0 / t×W0

   Curve = Exponential Then Stationary = Sigmoid

*Absolute vs Relative Growth*

Absolute = Total Growth per Unit Time = cm/day, g/day

Relative = Growth per Unit Time per Unit Initial = cm/cm/day, g/g/day

Example: Leaf A = 5cm² → 10cm² = 5cm² Absolute, 100% Relative

         Leaf B = 50cm² → 55cm² = 5cm² Absolute, 10% Relative

So Relative Growth = Better Comparison

### *3. CONDITIONS FOR GROWTH*

Water = Turgidity = Cell Enlargement = Enzymatic Activity

Oxygen = Aerobic Respiration = ATP for Growth

Nutrients = Macro + Micro = Protoplasm Synthesis

Temperature = Optimum 25-30°C = Enzymes Active

Light = Direction = Phototropism, Some Seed Germination Inhibit

### *4. DIFFERENTIATION, DEDIFFERENTIATION, REDIFFERENTIATION*

Differentiation = Cells from Meristem → Mature to Perform Specific Function

Example: Tracheary Elements = Lose Protoplasm = Conduct Water

Dedifferentiation = Mature Cells → Regain Meristematic Activity

Example: Cork Cambium from Cortex, Interfascicular Cambium from Medullary Ray

Redifferentiation = Dedifferentiated Cells → Again Lose Division = New Function

Example: Secondary Xylem, Secondary Phloem, Cork from Cork Cambium

*Figure 2: Development Cycle*

Seed → Embryo → Germination → Meristematic Cell

   ↓

Differentiation → Mature Cell = Xylem, Phloem, Parenchyma

   ↓ Injury/Hormone

Dedifferentiation → Cork Cambium, Interfascicular Cambium

   ↓

Redifferentiation → Secondary Xylem, Cork = Mature Again

### *5. PLANT GROWTH REGULATORS = PGR = Phytohormones* `5 Major = 2Q Pakka`

*A. AUXIN = IAA = Indole-3-Acetic Acid* `Growth Promoter`

Discovery = Charles Darwin + Francis = Coleoptile Phototropism = Canary Grass

F.W. Went = Avena Curvature Test = Agar Block with Auxin

Isolation = Kogl + Haagen Smit = Human Urine, Salkowski Test

Natural = IAA, IBA = Indole Butyric Acid

Synthetic = NAA = Naphthalene Acetic Acid, 2,4-D = 2,4-Dichlorophenoxyacetic

Site = Shoot Apical Meristem, Young Leaves, Developing Seeds

Functions:

1. Apical Dominance = Terminal Bud Inhibit Lateral Bud = Auxin from Apex

   Decapitation = Lateral Bud Grow = Pruning = Tea, Hedge

2. Cell Elongation = Acid Growth Hypothesis = H+ Pump = Cell Wall Loosen

3. Root Initiation = Stem Cutting = IBA, NAA Dip = Adventitious Root

4. Parthenocarpy = Seedless Fruit = Tomato, Brinjal = Auxin Spray

5. Weedicide = 2,4-D = Dicot Weeds Kill = Monocot Safe = Lawn

6. Prevent Abscission = Young Fruit + Leaves = Auxin Delay

7. Xylem Differentiation + Vascular Cambium Activity

Bioassay = Avena Curvature Test = Angle ∝ Auxin Conc.

*B. GIBBERELLIN = GA* `Growth Promoter`

Discovery = E. Kurosawa = Bakane Disease = Foolish Seedling = Rice = Fungus Gibberella fujikuroi

Chem = GA1, GA2, GA3 = Gibberellic Acid = Most Common = Fungal

Site = Young Leaves, Buds, Root Tips, Embryo

Functions:

1. Stem Elongation = Bolting = Rosette Plant = Cabbage, Beet = Internode Elongate + Flowering

2. Seed Germination = α-Amylase Synthesis = Barley Endosperm = Aleurone Layer

3. Fruit Growth = Grape Stalk Elongate = Size Increase

4. Delay Senescence = Fruit Can be Left Longer on Plant

5. Male Flower = Cannabis, Cucumber = Sex Expression

6. Replace Cold Treatment = Vernalization = Some Plants

7. Counteract Dormancy = Bud + Seed

Bioassay = Dwarf Pea/ Maize Test = Stem Elongation

*C. CYTOKININ = CK* `Growth Promoter`

Discovery = F. Skoog + Miller = Coconut Milk + DNA Degrade = Adenine Derivative

Natural = Zeatin = Corn Kernels + Coconut Milk, Isopentenyl Adenine

Synthetic = Kinetin = From Herring Sperm DNA, Benzyl Adenine

Site = Root Tip, Developing Seeds, Young Fruits

Functions:

1. Cell Division = Cytokinesis = Presence of Auxin Must = Skoog + Miller

2. Delay Senescence = Richmond-Lang Effect = Chlorophyll Retention = Spray on Leaves

3. Morphogenesis = Auxin High = Root, Cytokinin High = Shoot = Tissue Culture

4. Lateral Shoot Growth = Overcome Apical Dominance = With Auxin

5. Chloroplast Development + Nutrient Mobilization

6. Promote Seed Germination = Overcome Inhibitors

Bioassay = Tobacco Pith Callus Test, Radish Cotyledon Expansion

*D. ETHYLENE = Gaseous PGR* `Growth Inhibitor + Ripening`

Discovery = H.H. Cousins = Ripened Orange + Unripe Banana = Ripen Fast

Chem = C2H4 = Only Gaseous Hormone = Most Simple

Site = Ripening Fruits, Senescent Tissues, Nodes

Functions:

1. Fruit Ripening = Climacteric Fruits = Mango, Apple, Banana = Respiration Rise

2. Abscission = Leaves, Flowers, Fruits = Petiole Abscission Zone

3. Senescence = Aging = Chlorophyll Degrade

4. Epinasty = Petiole Bend Down = Leaf Drooping

5. Root Hair = Formation + Elongation

6. Breaking Dormancy = Peanut, Potato Bud

7. Triple Response = Pea Seedling = Reduced Elongation + Swelling + Horizontal Growth

8. Female Flower = Cucumber = Feminizing Effect

9. Apical Hook = Dicot Seedling = Protect Plumule

Bioassay = Triple Response in Pea, Abscission in Cotton

Commercial = Ethephon = Ethrel = Releases Ethylene = Pineapple Flowering, Tomato Ripen

*E. ABSCISIC ACID = ABA* `Growth Inhibitor = Stress Hormone`

Discovery = Addicott = Cotton Fruit Abscission = Abscisin II

Wereing = Bud Dormancy = Dormin

Both Same = ABA = Carotenoid Derivative

Site = Mature Leaves, Seeds, Stem = Chloroplast

Functions:

1. Stomata Closure = Drought Stress = Prevent Transpiration = Bind Guard Cell

2. Seed Dormancy = Inhibit Germination = Allow Seed Survive Stress

3. Bud Dormancy = Winter Buds = Deciduous Plants

4. Abscission = Leaves, Fruits = Layer Formation

5. Inhibit Cambium Activity = Growth Inhibit

6. Promote Senescence

7. Antagonist to GA = In Germination

Bioassay = Stomatal Closure Test, Seed Germination Inhibition

*Figure 3: PGR Summary Table*

**PGR** **Nature** **Main Role** **Bioassay** **Commercial Use**

**Auxin** Promoter Cell Elongation, Apical Dominance Avena Curvature 2,4-D Weedicide, IBA Rooting

**GA** Promoter Stem Elongation, Seed Germination Dwarf Pea Grape Size, Malting Barley

**Cytokinin** Promoter Cell Division, Delay Senescence Tobacco Callus Tissue Culture Shoot

**Ethylene** Inhibitor + Ripening Fruit Ripen, Abscission Triple Response Pea Ethrel = Pineapple Flower

**ABA** Inhibitor Stomata Close, Dormancy Stomata Closure Antitranspirant Spray

### *6. PHOTOPERIODISM = Flowering Response to Light/Dark* `Garner + Allard`

Critical Duration = Light + Dark Period = Flowering Control

SDP = Short Day Plant = Night Long = Flower = Xanthium, Soybean, Tobacco, Chrysanthemum

LDP = Long Day Plant = Night Short = Flower = Wheat, Radish, Spinach, Sugarbeet

DNP = Day Neutral = No Effect = Tomato, Cucumber, Cotton, Sunflower

Site = Leaves = Photoperiodic Stimulus, Shoot Apex = Flower Formation

Florigen = Hypothetical Hormone = Chailakhyan = Not Isolated Yet

Importance of Dark = Interruption of Dark by Flash = No Flowering in SDP

### *7. VERNALIZATION = Cold Treatment* `Low Temp Promote Flowering`

Discovery = Lysenko = Biennials = Cabbage, Carrot = Need Cold Winter

Process = Seeds/Plant + 1-5°C for 1-2 Months → Early Flowering

Site = Shoot Apical Meristem, Embryo

Vernalin = Hypothetical Hormone = Not Isolated

Example = Wheat, Barley, Rye = Winter Variety vs Spring Variety

Prevent Precocious Reproductive Development = Juvenile to Adult

### *8. SEED DORMANCY + GERMINATION*

Dormancy Cause = Hard Seed Coat, Immature Embryo, ABA High, Inhibitors

Methods Break = Scarification = Coat Break, Stratification = Cold, Light, GA Spray

Germination Condition = Water, O2, Temp, Light/Dark for Some

ABA : GA Ratio = High ABA = Dormant, High GA = Germinate

### *9. PYQ HOTSPOTS 2017-2024* 🔥

1. *Avena Curvature Test* = F.W. Went = Auxin Bioassay = NEET 2024

2. *Bakane Disease* = Gibberella fujikuroi = GA Discovery = NEET 2024

3. *Richmond-Lang Effect* = Cytokinin = Delay Senescence = NEET 2023

4. *Triple Response* = Ethylene = Pea Seedling = NEET 2023

5. *Florigen* = Hypothetical = Chailakhyan = Photoperiodism = NEET 2022

6. *Vernalization* = Cold Treatment = Winter Wheat = NEET 2022

7. *ABA* = Stress Hormone = Stomata Closure = NEET 2021

8. *2,4-D* = Auxin = Dicot Weedicide = NEET 2021

9. *Bolting* = GA = Internode Elongation + Flowering = NEET 2020

10. *SDP Example* = Xanthium, LDP = Wheat = NEET 2020

11. *Sigmoid Curve* = Lag + Log + Stationary = NEET 2019

12. *Apical Dominance* = Auxin from Apex = NEET 2019

13. *Cytokinin + Auxin* = Morphogenesis = Callus = NEET 2018

14. *Ethrel* = Ethephon = Releases Ethylene = NEET 2018

15. *Relative Growth Rate* = r = W1-W0/t×W0 = NEET 2017

### *10. GOOGLE SE HATKE TRICKS* 🧠

*A. PGR Yaad Karne Ka*

**A**uxin = **A**pical Dominance + **A**bscission Prevent

**G**A = **G**rowth + **G**ermination + **G**rape

**C**ytokinin = **C**ell Division + **C**hlorophyll Stay

**E**thylene = **E**very Fruit Ripe + **E**xit Leaf

**A**BA = **A**ll Band = **A**bscission + **A**nti-Growth

Trick: **A**unty **G**eeta **C**hachi **E**k **A**am

*B. Photoperiodism*

SDP = **S**hort **D**ay = **S**oybean, **S**ugarcane, **X**anthium

LDP = **L**ong **D**ay = **L**ettuce, **W**heat, **R**adish

DNP = **D**ay **N**eutral = **D**oes **N**ot Care = **T**omato, **C**otton

Trick: Dark Important = SDP Night Long, Flash Break = No Flower

*C. Growth Phases*

Lag = **L**ate Start, Log = **L**ot of Growth, Stationary = **S**top

Trick: **L**ife **L**oves **S**uccess

*D. Auxin vs Cytokinin Ratio*

Auxin High = Root, Cytokinin High = Shoot, Equal = Callus

Trick: **A** for **A**dventitious **R**oot, **C** for **C**allus **S**hoot

*Diagrams*: Sigmoid Curve, Apical Dominance, Photoperiodism, Vernalization  

*NEET Weightage*: 1Q PGR Function + 1Q Photoperiodism + 1Q Growth Curve = 8 Marks Pakka