🌱 Anatomy of Flowering Plants – Quick Intro 🔍 What is Anatomy?

🌱 Anatomy of Flowering Plants – Quick Intro 🔍 What is Anatomy?

• Anatomy = Study of internal structure and functional organization of organisms.

• In plants, it involves tissues, cells, and organs.

🧬 Hierarchy of Plant Structure

Level	Example
Cell	Parenchyma, collenchyma, etc.
Tissue	Meristematic, Permanent
Organ	Root, Stem, Leaf

🌾 Monocots vs Dicots (Anatomy Level)

Feature	Dicot	Monocot
Vascular bundles	Few, in a ring	Many, scattered
Secondary growth	Present	Absent
Pith	Prominent	Reduced/Absent
Vascular bundle type	Open (has cambium)	Closed (no cambium)

🌿 Adaptations in Internal Structures

• Hydrophytes: Aerenchyma for buoyancy.

• Xerophytes: Thick cuticle, sunken stomata.

• Halophytes: Special salt glands for excretion.

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Plant Tissues 📌 1. Meristematic Tissue

• Definition: Tissues with actively dividing cells.

• Features:

  • Thin cell walls

  • Dense cytoplasm

  • Large nucleus

  • No intercellular spaces

• Types:

  • Apical Meristem – at root and shoot tips (growth in length)

  • Intercalary Meristem – base of leaves or internodes (growth at specific points)

  • Lateral Meristem – along the sides (growth in thickness, e.g., vascular cambium)

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📌 2. Permanent Tissue

• Definition: Tissues with cells that have lost the power of division.

• Formed from: Meristematic tissues.

• Types:

(A) Simple Permanent Tissue

🔹 Parenchyma – Living, thin walls, large vacuole (storage & photosynthesis)
🔹 Collenchyma – Living, thick corners, flexible (support in dicot stems)
🔹 Sclerenchyma – Dead, thick lignified walls (mechanical strength)

(B) Complex Permanent Tissue

👉 Made of different types of cells working together.

• Xylem – Conduction of water

  • Tracheids, vessels, xylem fibres, xylem parenchyma

• Phloem – Transport of food

  • Sieve tubes, companion cells, phloem parenchyma, phloem fibres

🌿 Tissues in Plants – NEET Focus 🧩 What is a Tissue?

Tissue = Group of cells with a common origin and usually performing a common function.

🧪 Types of Plant Tissues 🌱 1. Meristematic Tissues (Actively dividing cells)

Feature	Description
💡 Function	Cell division (growth)
🌍 Location	Growing regions – tips of roots and shoots
💠 Characteristics	Small cells, dense cytoplasm, large nucleus, no vacuoles

🧠 Types:

Type	Location
Apical Meristem	Tips of root & shoot (↑ growth)
Intercalary Meristem	Base of leaves/internodes (length)
Lateral Meristem	Sides of stem/root (thickness – secondary growth)

🌿 2. Permanent Tissues (Non-dividing cells)

🪑 Formed from meristematic tissue, but lose ability to divide.

🍃 Types of Permanent Tissue: A. Simple Permanent Tissues (Made of one type of cell)

Tissue	Function	Key Points

Parenchyma

Storage, photosynthesis

Living cells, thin walls

Collenchyma

Flexibility

Thick corners, living

Sclerenchyma

Strength

Dead, thick lignified walls

B. Complex Permanent Tissues (More than one cell type)

Tissue	Function
Xylem	Water conduction (🧊)
Phloem	Food transport (🍬)

🌱 Meristematic Tissues – NEET Notes

Meristems are regions in plants with active cell division, responsible for growth.
(Greek: meristos = divisible)

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📚 Types of Meristematic Tissue

Type	Location	Function	Special Notes
Apical Meristem	Tips of roots & shoots	Primary growth – Increases length	Produces primary tissues. Forms axillary buds that can grow into branches/flowers.
Intercalary Meristem	Between mature tissues, like at base of leaves or internodes	Regrowth in length	Found in grasses; helps in regeneration after grazing.
Lateral Meristem (Secondary Meristem)	Mature regions of stem/root (in woody plants)	Secondary growth – Increases girth	Includes:

• Vascular cambium

• Interfascicular cambium

• Cork cambium |

🌿 Primary vs Secondary Meristem

Feature	Primary Meristem	Secondary Meristem
Appearance	Early in plant’s life	Later stage (woody plants)
Growth Type	Primary growth (↑ length)	Secondary growth (↑ thickness)
Examples	Apical, Intercalary	Lateral (vascular & cork cambium)

🔄 What Happens After Cell Division?

• New cells from meristems become:

  • Specialised

  • Mature

  • Lose ability to divide → Form Permanent Tissues

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🌈 Bonus: Apical Meristem Produces

• Dermal tissue → Outer protective layer

• Ground tissue → Basic plant support/storage

• Vascular tissue → Xylem & Phloem

🌱 Permanent Tissues – NEET Notes

Permanent tissues are made of mature, non-dividing cells that are specialised for a specific function.

🧬 Types of Permanent Tissues

1. Simple Tissues → Made of one type of cell

2. Complex Tissues → Made of more than one type of cell (like xylem, phloem)

1⃣ SIMPLE TISSUES 📘 1. Parenchyma

Feature	Description
Structure	Thin-walled, isodiametric (round, oval, polygonal etc.)
Cell Wall	Made of cellulose
Arrangement	Loose with small intercellular spaces
Functions	✅ Photosynthesis (if chloroplasts present – called chlorenchyma)
✅ Storage, Secretion
✅ Wound healing
Location	Soft parts of plants – pith, cortex, mesophyll, etc.

📗 2. Collenchyma

📗 2. Collenchyma

Feature	Description
Structure	Thickened at corners due to cellulose, hemicellulose & pectin
Cell Shape	Oval, spherical or polygonal
Special Feature	No intercellular spaces, sometimes contain chloroplasts
Functions	✅ Mechanical support to growing parts
✅ Photosynthesis (when chloroplasts are present)
Location	Below epidermis in dicot stems, petioles

📙 3. Sclerenchyma

📙 3. Sclerenchyma

Feature	Description
Structure	Thick, lignified walls, dead cells, no protoplast
Types	🔹 Fibres – long, pointed, thick-walled, in bundles
🔹 Sclereids – round, oval, short, very thick-walled
Functions	✅ Mechanical strength
Location
🔸 Sclereids – found in nutshells, pulp of fruits (guava, pear), seed coats, tea leaves
🔸 Fibres – present in stems, bark, vascular bundles

🧠 Quick Memory Trick

PCS for simple tissues

:

• P → Parenchyma (Photosynthesis + Packing)

• C → Collenchyma (Corners + Chloroplast)

• S → Sclerenchyma (Strength + Support)

🌱 Complex Tissues – NEET Notes

Complex tissues are made of more than one type of cell, all working together for a common function.

Xylem – Water & Mineral Transport 🚰

🔹 Component	🔸 Description
Function	Conducts water & minerals upward from roots → stems → leaves + provides mechanical strength
Made of	🔹 Tracheids
🔹 Vessels
🔹 Xylem fibres
🔹 Xylem parenchyma

🌾 Xylem Elements

🌾 Xylem Elements

Element	Type	Function & Structure
Tracheids	Dead	🔸 Long, tapered ends
🔸 Lignified thick walls
🔸 Found in gymnosperms & angiosperms
🔸 Main conducting tissue in gymnosperms
Vessels	Dead	🔸 Long tube-like, made of vessel elements
🔸 Have perforations → continuous column
🔸 Found only in angiosperms
Xylem fibres	Dead	🔸 Thick-walled, narrow
🔸 Give mechanical support
Xylem parenchyma	Living	🔸 Store food (starch, fats, tannins)
🔸 Help in radial conduction of water (sideways movement)

🔄 Types of Primary Xylem

🔄 Types of Primary Xylem

Type	Description
Protoxylem	First-formed xylem (small lumen, few thickenings)
Metaxylem	Later-formed xylem (large lumen, more thickening)

• Endarch: Protoxylem towards pith (stem)

• Exarch: Protoxylem towards periphery (root)

Phloem – Food Transport 🍞

2⃣ Phloem – Food Transport 🍞

🔹 Component	🔸 Description
Function	Transports food (sucrose) from leaves to other parts (translocation)
Made of	🔹 Sieve tube elements
🔹 Companion cells
🔹 Phloem parenchyma
🔹 Phloem fibres

🌿 Phloem Elements

🌿 Phloem Elements

Element	Type	Function & Structure
Sieve Tube Elements	Living (without nucleus)	🔸 Main conducting cells
🔸 Have sieve plates (with pores)
🔸 No nucleus, but active
Companion Cells	Living	🔸 Connected to sieve tubes via plasmodesmata
🔸 Help sieve tubes in functioning
Phloem Parenchyma	Living	🔸 Store food and resins, latex etc.
Phloem Fibres (Bast fibres)	Dead	🔸 Provide mechanical strength
🔸 Only dead component of phloem

📌 In monocots, phloem parenchyma is absent.

💡 Quick Tip to Remember

📚 Xylem = Xtra Water → dead elements except parenchyma
📚 Phloem = Food Phone Line → living (except fibres)

🌿 Phloem – Detailed Notes (NEET Ready)

📦 Function: Transports food (mainly sucrose) from leaves → other parts of plant = Translocation

🧬 Phloem Components (Angiosperms)

🔹 Tissue	🔸 Type	🧠 Key Functions & Features
Sieve Tube Elements	Living (no nucleus)	🔸 Long tube-like, arranged longitudinally
🔸 Sieve plates at end walls (perforated)
🔸 No nucleus, has cytoplasm + large vacuole
🔸 Function regulated by Companion Cell
Companion Cells	Living	🔸 Nucleated, thin-walled
🔸 Connected to sieve tubes via pit fields
🔸 Maintain pressure gradient
🔸 Control sieve tube activity
Phloem Parenchyma	Living	🔸 Cylindrical, tapering, nucleated
🔸 Store food, resins, mucilage, latex
🔸 Absent in monocots
Phloem Fibres (Bast Fibres)	Dead	🔸 Thick-walled, sclerenchymatous
🔸 Found in secondary phloem
🔸 Used in industry: jute, flax, hemp
🔸 Absent in primary phloem

🌲 Phloem in Gymnosperms

🧾 Tissue	🧠 Info
Sieve Cells	Present instead of sieve tubes
Albuminous Cells	Replace companion cells
🔸 Sieve Tubes + Companion Cells	❌ Absent

🕰 Primary Phloem Types

Type	Features
Protophloem	🔸 First formed
🔸 Narrow sieve tubes
Metaphloem	🔸 Formed later
🔸 Wider sieve tubes

🧠 Quick Visual Association

Phloem Tissue	Memory Trick
Sieve Tube	🍝 Like pasta tubes – conduct food
Companion Cell	💁‍♀ Helper cell (with nucleus)
Phloem Parenchyma	🧃 Stores juices (resin, latex)
Phloem Fibre	🪢 Tough like rope – Jute

🌿 TISSUE SYSTEM IN PLANTS (NEET Notes)

🧩 Based on location and structure, tissues are grouped into three main systems:

1⃣ Epidermal Tissue System

📍 Location: Outer protective covering of entire plant body (young stems, roots, leaves, flowers)

🔹 Key Components:

Component	Function
Epidermis	Single layer, protective barrier
Cuticle	Waxy layer (made of cutin), reduces water loss
Stomata	Regulate gas exchange & transpiration
Trichomes (shoot)	Hair-like, prevent water loss, defense
Root Hairs	Increase surface area for water absorption

2⃣ Ground (Fundamental) Tissue System

📍 Location: All tissue except epidermis and vascular tissue

🔹 Key Components:

Region	Tissue	Function
Cortex	Mostly parenchyma	Storage
Endodermis	Innermost cortex layer	Controls water movement
Pericycle	Just outside vascular tissue	Lateral root initiation
Pith/Medulla	Center part (stem)	Storage, sometimes support

3⃣ Vascular (Conducting) Tissue System

📍 Location: In vascular bundles (roots, stems, leaves)

🔹 Key Components:

Tissue	Function
Xylem	Transports water + minerals (roots → shoots)
Phloem	Transports food (leaves → other parts)

📌 Vascular Bundles:

• Conjoint (xylem + phloem together)

• Radial (xylem & phloem separate, alternate) – common in roots

• Open (with cambium – can do secondary growth) / Closed (no cambium – no secondary growth)

🧠 NEET QUICK RECALL TRICKS:

• Epidermis = Skin of plant 🌿

• Ground Tissue = Filler & support 🧱

• Vascular Tissue = Transport system 🚚

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🌿 ANATOMY OF DICOT ROOT (e.g., Sunflower Root) 📸 Transverse Section (T.S.) – What You'll See:

From outside to inside ⬇

1⃣ Epidermis (Rhizodermis / Epiblema)

• Outermost layer

• Unicellular root hairs present 🌱 (absorb water)

• No cuticle

2⃣ Cortex

• Several layers of parenchyma cells (thin-walled, loosely packed)

• Intercellular spaces for gas exchange

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3⃣ Endodermis

• Innermost layer of cortex

• Barrel-shaped cells, no intercellular spaces

• Casparian Strips on radial and tangential walls (suberin deposition – water-impermeable 🚫💧)

4⃣ Pericycle

• Just inside endodermis

• Thick-walled parenchyma

• Origin of:

  • Lateral roots 🌱

  • Vascular cambium (in secondary growth) 🌳

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5⃣ Vascular Bundles

• Radial arrangement (xylem and phloem alternate)

• Exarch xylem (protoxylem towards periphery, metaxylem towards centre) 🔁

• Usually diarch to tetrarch (2–4 xylem patches)

• Conjunctive tissue: Parenchyma between xylem & phloem

6⃣ Pith

• Small or absent (inconspicuous) in dicot root

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💡 STELE = All tissues inner to endodermis

🧩 Includes: Pericycle + Vascular bundles + Pith

🧠 NEET KEY POINTS TO REMEMBER:

Feature	Dicot Root
Xylem & Phloem	Radial
Xylem Type	Exarch
Vascular Bundles	2–4 (diarch to tetrarch)
Pericycle	Forms lateral roots & vascular cambium
Pith	Small or absent

🌾 ANATOMY OF MONOCOT ROOT (e.g., Maize Root) 📸 Transverse Section (T.S.) – What You’ll See:

Just like dicot root, arranged from outside to inside, but with key differences! 👇

1⃣ Epidermis (Rhizodermis)

• Outermost layer

• Unicellular root hairs present

• No cuticle

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2⃣ Cortex

• Multiple layers of parenchyma

• Intercellular spaces for aeration

3⃣ Endodermis

• Barrel-shaped cells

• With Casparian strips (suberin)

• Controls water flow into stele

4⃣ Pericycle

• Thin layer just inside endodermis

• No lateral roots or vascular cambium initiation here (because NO secondary growth!)

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5⃣ Vascular Bundles

• Radial and Polyarch (more than 6 xylem bundles 🔟+)

• Exarch xylem (protoxylem towards outside)

• Xylem and phloem alternate

• No cambium ➡ no secondary growth

6⃣ Pith

• Large and well-developed (unlike dicot root) 💡

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🌟 KEY DIFFERENCES: Dicot Root vs Monocot Root

Feature	Dicot Root	Monocot Root
Xylem Bundles	2–4 (Diarch–Tetrarch)	>6 (Polyarch)
Pith	Small or absent	Large & well developed
Secondary Growth	Present 🌳	Absent 🚫🌳
Cambium	Forms during growth	Absent

🔍 NEET Exam Tip:

"Polyarch + No secondary growth + Big pith = Monocot Root" – lock it in! 🔒🧠

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🌿 ANATOMY OF DICOT STEM

(Example: Sunflower Stem)

🔬 Transverse Section (T.S.) shows these layers (Outside to Inside):

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🌿 ANATOMY OF DICOT STEM

(Example: Sunflower Stem)

🔬 Transverse Section (T.S.) shows these layers (Outside to Inside):

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2⃣ Cortex

👉 Divided into 3 zones:

Sub-zone	Tissue Type	Function
Hypodermis	Collenchyma	Mechanical support to young stem
General cortex	Parenchyma	Storage + Intercellular spaces
Endodermis	Parenchyma rich in starch	Called Starch sheath 🍚

3⃣ Pericycle

• Sclerenchyma patches (semi-lunar)

• Located just inside endodermis,

🌱 ANATOMY OF MONOCOT STEM

(Example: Maize stem)

🔬 Key Features (T.S. View):

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1⃣ Epidermis

• Outermost single cell layer

• Covered by cuticle

• Protective function 🛡

2⃣ Hypodermis

• Sclerenchymatous (not collenchyma like dicots)

• Provides mechanical strength 💪

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3⃣ Ground Tissue

• Large, parenchymatous, no clear cortex/pith separation

• Fills most of the stem 🧱

• Storage and basic support

4⃣ Vascular Bundles

• Scattered throughout ground tissue (NO ring formation❌)

• Conjoint & Closed (no cambium = no secondary growth)

• Surrounded by a sclerenchymatous bundle sheath 🔒

• Peripheral bundles smaller, central bundles larger

5⃣ Phloem

• Lacks phloem parenchyma ❌

• Sieve tubes + Companion cells present

6⃣ Xylem

• Contains water-filled cavities 💧 inside vascular bundles

• Helps in water conduction & pressure regulation

🍃 ANATOMY OF DORSIVENTRAL (DICOTYLEDONOUS) LEAF

(e.g., sunflower leaf)

🔍 1. Epidermis

• Two layers:
  🔸 Adaxial (upper) epidermis – thick cuticle, fewer or no stomata
  🔸 Abaxial (lower) epidermis – more stomata, thinner cuticle

• Function: Protection + gas exchange 🌬

🌿 2. Mesophyll (photosynthetic layer)

Made of parenchyma cells containing chloroplasts 🌞

📏 2 Types:

• 🔹 Palisade parenchyma (upper side)

  • Elongated, vertical, tightly packed

  • Rich in chloroplasts

  • Main site of photosynthesis 🧪

• 🔸 Spongy parenchyma (lower side)

  • Loosely arranged, round/oval cells

  • Air spaces → helps in gas exchange

  • Fewer chloroplasts

💧 3. Vascular System (veins & midrib)

• Made of vascular bundles:

  • Surrounded by bundle sheath (thick-walled)

  • Xylem: towards adaxial (upper) side 🌊

  • Phloem: towards abaxial (lower) side 🍭

• Veins show reticulate venation – network-like

QUICK TIPS:

• Mesophyll is differentiated (palisade + spongy)

• Xylem up, Phloem down (think: XP → xylem-phloem!)

• More stomata on lower surface

🌿 ANATOMY OF ISOBILATERAL (MONOCOT) LEAF

(e.g., grass leaf)

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🔍 1. Epidermis

• Present on both surfaces:
  🔸 Adaxial (upper) & 🔹 Abaxial (lower) epidermis

• Stomata on both sides (unlike dicot)

• Cuticle present on both sides

• Bulliform cells (special feature!):

  • Found in adaxial epidermis

  • Large, empty, colourless cells

  • Help in rolling/unrolling of leaves during water stress 💧➡🍃

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🌱 2. Mesophyll

• Not differentiated into palisade & spongy parenchyma ❌

• All cells are parenchymatous and contain chloroplasts for photosynthesis ☀

📌 QUICK TIPS:

x

• Vascular bundles are conjoint and closed

• Arranged in parallel venation

• Similar size bundles (except larger ones in midrib)

• Bundle sheath present

📌 QUICK TIPS:

• Stomata on both sides

• Bulliform cells → key monocot feature!

• Parallel venation

• Mesophyll is undifferentiated

• Adapted for water conservation and sunlight capture 🌞

🌱 Vascular Cambium & Cambial Ring Formation 🧠 What is Vascular Cambium?

• A lateral meristem that produces secondary xylem (wood) & secondary phloem

• Responsible for secondary growth (increase in thickness)

In a young dicot stem, vascular cambium is initially:

A) Absent
B) Present as a continuous ring
C) Present as patches between xylem and phloem
D) Present in the medullary rays only

✅ Correct Answer:

C) Present as patches between xylem and phloem

💡Explanation:

As per NCERT, in the young dicot stem, the vascular cambium is not initially a complete ring. It exists in small patches between xylem and phloem of vascular bundles. Later, it develops into a continuous cambial ring during secondary growth.

Which of the following best describes the role of vascular cambium?

A) Helps in absorption of water
B) Produces new epidermal cells
C) Cuts off new xylem and phloem tissues
D) Causes elongation of root tips

✅ Answer: C
Explanation: Vascular cambium is a lateral meristem that cuts off secondary xylem and phloem during secondary growth.

In the young dicot stem, the vascular cambium is:

A) Present as a complete ring
B) Found in medullary rays only
C) Found as scattered patches between xylem and phloem
D) Present in phloem only

✅ Answer: C
Explanation: Initially, it appears as patches between xylem and phloem, which later connect to form a continuous ring.

The vascular cambium ring is completed by:

A) Activity of cork cambium
B) Fusion of intrafascicular and interfascicular cambium
C) Lenticel formation
D) Fusion of pericycle and endodermis

✅ Answer: B
Explanation: Intrafascicular cambium (within vascular bundles) and interfascicular cambium (between bundles) fuse to form the ring.

Which of the following tissues originates from vascular cambium?

A) Parenchyma
B) Sclerenchyma
C) Secondary xylem
D) Primary phloem

✅ Answer: C
Explanation: Vascular cambium gives rise to secondary vascular tissues, especially secondary xylem and phloem.

Which meristem is responsible for the increase in girth of the plant stem?

A) Apical meristem
B) Lateral meristem (vascular cambium)
C) Intercalary meristem
D) None of the above

✅ Answer: B
Explanation: Lateral meristem, i.e., vascular cambium, causes secondary growth, increasing stem thickness.

Assertion (A): In a dicot stem, vascular cambium ring is formed from both intrafascicular and interfascicular cambium.
Reason (R): Cells of medullary rays become meristematic and form the interfascicular cambium.

A) Both A and R are true, and R is the correct explanation of A
B) Both A and R are true, but R is not the correct explanation of A
C) A is true, but R is false
D) A is false, but R is true

✅ Answer: A
Explanation: Both statements are correct, and R explains how interfascicular cambium is formed.

🌿 Diagram-based MCQ: Q7.

In the transverse section of a young dicot stem, where would you find the interfascicular cambium developing?

A) Between the phloem and cortex
B) In the center of xylem
C) Between two vascular bundles, in medullary rays
D) Inside pith region

✅ Answer: C
Explanation: Interfascicular cambium arises from medullary ray cells between vascular bundles

What triggers the formation of a continuous cambium ring in a dicot stem?

A) Formation of root hairs
B) Thickening of the cortex
C) Meristematic activity of medullary ray cells
D) Activity of cork cambium

✅ Answer: C
Explanation: Medullary ray cells between vascular bundles become meristematic, forming interfascicular cambium that completes the cambial ring.

🔄 Types of Cambium in Dicot Stem

Cambium Type	Location
Intrafascicular Cambium	Between primary xylem & phloem (within vascular bundles)
Interfascicular Cambium	Formed from medullary ray cells (between vascular bundles)

🌳 Formation of Cambial Ring (Step-by-Step)

1⃣ Young Dicot Stem

• Intrafascicular cambium exists within vascular bundles

2⃣ Medullary Ray Activation

• Medullary ray cells become meristematic

3⃣ Interfascicular Cambium Formation

• These meristematic ray cells form interfascicular cambium

4⃣ Continuous Cambial Ring

• Intra + Interfascicular cambium unite to form a complete ring of vascular cambium

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Interfascicular cambium is formed from:

A) Apical meristem
B) Xylem parenchyma
C) Medullary ray cells
D) Pith cells

✅ Answer: C
📘 Explanation: The medullary ray cells (which are parenchymatous) become meristematic to form interfascicular cambium.

The continuous cambial ring in dicot stems is formed by the fusion of:

A) Phloem and xylem
B) Pith and cortex
C) Intrafascicular and interfascicular cambium
D) Apical and intercalary meristem

✅ Answer: C
📘 Explanation: Intrafascicular + Interfascicular cambium = Cambial ring ➡ responsible for secondary growth.

Which of the following statements is correct?

A) Cambial ring formation occurs in monocots
B) Interfascicular cambium originates from vascular bundles
C) Intrafascicular cambium is formed from medullary rays
D) Interfascicular cambium forms outside the vascular bundles

✅ Answer: D
📘 Explanation: Interfascicular cambium develops between vascular bundles, outside the bundle, from medullary rays.

What does the cambial ring cut off towards the inner side?

A) Secondary phloem
B) Secondary cortex
C) Secondary xylem
D) Cork cells

✅ Answer: C
📘 Explanation: Cambium cuts cells towards the pith (inner side), which mature into secondary xylem.

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Which of the following is TRUE about cambial activity?

A) Cambium is equally active on both sides
B) More secondary phloem is formed than secondary xylem
C) Cambium is more active on inner side, forming more secondary xylem
D) Primary phloem becomes secondary phloem

✅ Answer: C
📘 Explanation: Cambium shows more activity on the inner side, leading to more secondary xylem than phloem.

What happens to the primary and secondary phloem during secondary growth?

A) They increase in size
B) They form cork
C) They get gradually crushed
D) They turn into secondary xylem

✅ Answer: C
📘 Explanation: The accumulation of secondary xylem compresses and crushes the phloem layers.

What remains intact near the center of the stem even after secondary growth?

A) Secondary phloem
B) Secondary cortex
C) Primary xylem

D) Epidermis

✅ Answer: C
📘 Explanation: Despite secondary growth, the primary xylem remains more or less intact, near the pith.

What are secondary medullary rays, and where do they form?

A) Narrow bands of xylem near the epidermis
B) Bands of sclerenchyma formed outside the phloem
C) Bands of parenchyma passing radially through secondary xylem and phloem
D) Compressed regions of primary xylem

✅ Answer: C
📘 Explanation: Secondary medullary rays are parenchymatous bands that run radially, allowing lateral transport and storage.

🌳 Spring Wood vs Autumn Wood – Annual Rings

Feature	🌸 Spring Wood (Early Wood)	🍂 Autumn Wood (Late Wood)
Season	Formed in spring	Formed in autumn/winter
Cambium Activity	Highly active	Less active
Xylary Elements	More numerous, with wider vessels	Fewer, with narrow vessels
Appearance	Lighter in colour, lower density	Darker in colour, higher density
Growth Rate	Fast growth	Slow growth
Function	Facilitates rapid conduction of water	Provides mechanical strength
Annual Ring	One spring wood + one autumn wood = 1 annual ring
Use in Age Determination	Used to estimate tree age	✅ Yes, together with spring wood

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🔔 Key Point:
In temperate regions, trees form annual rings due to seasonal variation in cambial activity. Counting these rings reveals the tree’s age!

In which season is cambium most active, producing xylem with wider vessels?

A) Summer
B) Autumn
C) Winter
D) Spring

✅ Answer: D
📘 Explanation: In spring, cambium activity is high → more xylem → wider vessels → spring wood/early wood.

Annual rings are formed due to:

A) Formation of only spring wood
B) Alternate arrangement of primary xylem and phloem
C) Alternate appearance of spring wood and autumn wood
D) Continuous activity of cork cambium

✅ Answer: C
📘 Explanation: Spring wood + Autumn wood = 1 annual ring. These appear as concentric rings in stems.

How can the age of a tree be estimated?

A) By counting medullary rays
B) By counting lenticels
C) By counting annual rings in the stem
D) By measuring the diameter of xylem

✅ Answer: C
📘 Explanation: Each annual ring = 1 year. Count the rings in T.S. of stem to know the tree’s age.

Which of the following characteristics is true for autumn wood?

A) Lighter in color, low density
B) Vessels with wider cavities
C) Formed when cambium is highly active
D) Narrow vessels, darker wood, high density

✅ Answer: D
📘 Explanation: Autumn wood forms in winter, has narrow vessels, is darker and denser.

Why is spring wood lighter in color than autumn wood?

A) Due to higher tannin content
B) Due to wider vessels and lower density
C) Due to thicker cell walls
D) Because it is formed from primary xylem

✅ Answer: B
📘 Explanation: Spring wood has larger vessels, making it less dense and thus lighter in color.

Each combination of spring wood + autumn wood = ?

A) One vascular bundle
B) One medullary ray
C) One annual ring
D) One cambium ring

✅ Answer: C
Explanation: One spring + one autumn wood band = 1 annual ring, which helps estimate tree age.

If the diagram above has 4 spring wood + 3 autumn wood bands, what is the age of the tree?

A) 3 years
B) 4 years
C) 7 years
D) 1 year

✅ Answer: B
Explanation: Number of complete spring + autumn pairs = 3 → but we see a 4th spring forming → 4 years.

Why is heartwood darker in color?

A) Due to thickening of primary xylem
B) Due to deposition of organic compounds like tannins and resins
C) Because it conducts more water
D) Because it contains living parenchyma

✅ Answer: B
📘 Explanation: Heartwood is dark because of tannins, resins, oils, gums, and aromatic substances.

🌲 Q2.

Which of the following is true for heartwood?

A) Conducts water
B) Involved in mineral transport
C) Provides mechanical support
D) Contains active living cells

✅ Answer: C
📘 Explanation: Heartwood is dead, does not conduct water, but provides strength and support.