🔑 Target Keywords:
plant growth and development neet notes, plant hormones neet, photoperiodism, vernalization, auxin gibberellin cytokinin ethylene
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🌿 Introduction – Let’s Grow Like a Plant!
Hello NEET Aspirants 👋
Aaj hum ek bahut hi conceptual aur interesting chapter start kar rahe hain —
Plant Growth and Development.
Ye chapter plants ke growth, differentiation, hormones, aur environmental control ke bare me batata hai.
Jitna simple lagta hai, utna hi NEET me 3–4 marks ke guaranteed questions deta hai! 🌱✨
So, let’s understand this in the easiest Hinglish style 👇
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🌱 1. What Is Growth?
Definition (NCERT-based):
> “Growth is an irreversible permanent increase in size, volume, or number of cells.”
Simple words me:
Growth ka matlab hai plant ka continuously bada hona — size me, length me, ya cell number me.
Example:
Root tip ka continuously bada hona 🌾
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🌿 2. Characteristics of Growth
1. Irreversible: Once grown, can’t go back.
2. Permanent: Long-term change in size.
3. Quantitative: Measured in length, mass, or volume.
4. Cell-based: Cell division + enlargement = growth.
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🌿 3. Phases of Growth
Phase Description Example
1. Lag Phase Initial slow growth Young seedling
2. Log/Exponential Phase Rapid cell division Elongating stem
3. Stationary Phase Growth slows/stops Mature plant
📈 Graphically, it’s a Sigmoid Growth Curve (S-shaped) curve.
💡 Trick to remember:
“Lag – Log – Level” = Growth phases
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🌾 4. Growth Measurement
Growth ko measure karne ke liye Auxanometer use hota hai.
Unit: cm/hr or mm/day
Formula:
\text{Relative Growth Rate} = \frac{\text{Increase in size}}{\text{Original size × Time}}
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🌸 5. Types of Growth
Type Description Example
Arithmetic Growth Only one daughter cell divides Root elongation
Geometric Growth Both daughter cells divide Early embryo
💡 Trick:
Arithmetic = Linear 📏
Geometric = Exponential 📈
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🌻 6. Growth at Cellular Level
Growth involves 3 major processes 👇
1. Cell Division (Mitosis) – In meristematic regions
2. Cell Enlargement – Due to water & nutrients
3. Cell Differentiation – Cells get specialized for specific functions
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🌿 7. Plant Growth Regulators (PGRs / Plant Hormones)
Plant growth is regulated by five major hormones — also called phytohormones.
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🌱 A. Auxins – The Growth Hormone
Feature Description
Discovery F.W. Went (1928) from oat coleoptile
Main Hormone Indole-3-Acetic Acid (IAA)
Site of Synthesis Shoot tip, young leaves
Functions
Cell elongation
Apical dominance
Root initiation in cuttings
Delay abscission
Fruit development (Parthenocarpy in tomato)
💡 Trick: Auxin = “Always Upwards” growth 🌿
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🌾 B. Gibberellins – The Growth Promoters
Feature Description
Discovered by Kurosawa (from fungus Gibberella fujikuroi)
Example GA₃
Functions
Stem elongation
Breaking dormancy in seeds
Bolting in rosette plants (onion, beet)
Fruit growth (grapes, apples)
💡 Trick: Gibberellin = “Grow tall like bamboo!” 🎋
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🌻 C. Cytokinins – The Cell Dividers
Feature Description
Discovered by Skoog & Miller
Example Kinetin, Zeatin
Site of Synthesis Root tips, developing fruits
Functions
Promotes cell division (cytokinesis)
Delays senescence (aging)
Helps in tissue culture (with auxin)
💡 Trick: Cytokinin = “Stay Young Hormone” 🌿
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🍁 D. Abscisic Acid (ABA) – The Stress Hormone
Feature Description
Nature Growth inhibitor
Functions
Induces dormancy in seeds
Closes stomata during stress
Promotes senescence
Opposite of gibberellins
💡 Trick: ABA = “Always Be Alert” (Stress response) ⚡
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🍌 E. Ethylene – The Ripening Hormone
Feature Description
Nature Only gaseous hormone
Functions
Fruit ripening
Epinasty (downward bending)
Breaks dormancy
Promotes abscission
Triple response (inhibits elongation, increases girth)
💡 Trick: Ethylene = “Eat ripe banana!” 🍌
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🌾 8. Photoperiodism
Definition:
> “Response of plants to the relative length of day and night.”
Type Example
Short-day plants Rice, Chrysanthemum
Long-day plants Wheat, Barley
Day-neutral plants Tomato, Cucumber
💡 Photoreceptor: Phytochrome
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❄️ 9. Vernalization
Definition:
> “The process of promoting flowering by exposure to low temperature.”
Example: Wheat, Mustard 🌼
Site: Shoot apex
Hormone involved: Vernalin
💡 Trick: Winter = Vernalization season! ❄️
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🌿 10. Plant Movements
Type Description Example
Tropic Movements Directional (toward stimulus) Phototropism, Geotropism
Nastic Movements Non-directional Touch-me-not (Mimosa)
💡 Trick: Tropic = Targeted, Nastic = Natural 😄
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🧠 11. NEET PYQs (2018–2024)
Year Question Answer
2020 Hormone causing fruit ripening Ethylene
2021 Hormone breaking seed dormancy Gibberellin
2022 Opposite action to gibberellins Abscisic acid
2023 Short-day plant example Rice
2024 Bolting induced by? Gibberellin
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🧾 12. Quick Summary Chart
Hormone Nature Function Example
Auxin Growth promoter Cell elongation Root initiation
Gibberellin Growth promoter Stem elongation Bolting
Cytokinin Growth promoter Cell division Tissue culture
ABA Growth inhibitor Dormancy, closure Stress response
Ethylene Gaseous hormone Ripening Banana, Mango
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🎯 13. NEET Strategy
1. Learn all five hormones with full function list.
2. Practice differences (Auxin vs Gibberellin, etc.).
3. Memorize Photoperiodism + Vernalization.
4. Revise NCERT diagrams (Fig. 15.1 to 15.5).
5. Solve last 10 years’ PYQs — direct lines repeat!
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🔗 Related Blogs
☀️ Photosynthesis in Higher Plants – Day 50
🌬️ Respiration in Plants – Day 51
🌸 Anatomy of Flowering Plants – Day 49
🍃 Transport in Plants – Day 20
🌿 [Plant Growth Regulators Chart PDF – Coming Soon!]
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🏁 Conclusion
Plant Growth and Development ek conceptual + memory-based chapter hai.
Agar aapko hormones aur unke functions clear hain, toh NEET ke 3–4 marks aapke fixed hain 🌱