🌱 Plant Growth and Development – NEET 2025 Complete Notes (With Diagrams & PYQs)

🔑 Target Keywords:

plant growth and development neet notes, plant hormones neet, photoperiodism, vernalization, auxin gibberellin cytokinin ethylene

---

🌿 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 👇

---

🌱 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 🌾

---

🌿 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.

---

🌿 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

---

🌾 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}}

---

🌸 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 📈

---

🌻 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

---

🌿 7. Plant Growth Regulators (PGRs / Plant Hormones)

Plant growth is regulated by five major hormones — also called phytohormones.

---

🌱 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 🌿

---

🌾 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!” 🎋

---

🌻 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” 🌿

---

🍁 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) ⚡

---

🍌 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!” 🍌

---

🌾 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

---

❄️ 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! ❄️

---

🌿 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 😄

---

🧠 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

---

🧾 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

---

🎯 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!

---

🔗 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!]

---

🏁 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 🌱