ANATOMY OF FLOWERING PLANTS

 

What is Plant Anatomy?

• Plant anatomy is the study of internal structure and organization of tissues in plants.
• It helps in understanding:
  • Functional adaptation
  • Transport system
  • Growth patterns

Tissue Organization in Flowering Plants

Flowering plants have three major tissue systems:

 Epidermal Tissue System

Components:

1. Epidermis
   • Single layer of compact cells
   • No intercellular spaces
   • Covered by cuticle (except roots)
2. Cuticle
   • Made of cutin
   • Prevents water loss
3. Stomata
   • Present mainly on leaves
   • Composed of guard cells
   • Regulate:
     • Gas exchange
     • Transpiration
4. Root hairs
   • Extensions of epidermal cells
   • Increase surface area for absorption
5. Trichomes (in stem)
   • Hair-like structures
   • Protection + reduce transpiration

 Functions:

• Protection
• Water conservation
• Gas exchange

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🌿 B. Ground Tissue System

 Types of Ground Tissue:

1. Parenchyma

• Living cells, thin cell wall
• Large vacuole
• Functions:
  • Storage
  • Photosynthesis (chlorenchyma)
  • Air storage (aerenchyma)

2. Collenchyma

• Living cells with uneven thickening
• Located below epidermis
• Provides flexibility + support

3. Sclerenchyma

• Dead cells with lignified thick walls
• Types:
  • Fibres
  • Sclereids
• Provides mechanical strength

 Vascular Tissue System

 Xylem (Water Transport)

Components:

• Tracheids → elongated, dead
• Vessels → wide tubes (advanced plants)
• Xylem fibres → support
• Xylem parenchyma → storage

👉 Function: Transport water & minerals (root → shoot)

Phloem (Food Transport)

Components:

• Sieve tubes → transport sugars
• Companion cells → assist sieve tubes
• Phloem fibres → strength
• Phloem parenchyma → storage

👉 Function: Transport food (source → sink)

Types of Vascular Bundles:

• Radial → root
• Conjoint → stem/leaf
  • Collateral
  • Bicollateral
• Open (with cambium) → dicots
• Closed (without cambium) → monocots

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🌳 3. Anatomy of Plant Organs

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🌱 A. Root Anatomy

 Layers:

1. Epiblema (epidermis) → root hairs present
2. Cortex → parenchymatous, storage
3. Endodermis
   • Casparian strips (suberin)
   • Controls water entry
4. Pericycle
   • Gives rise to lateral roots
5. Vascular bundles
   • Radial arrangement

 Dicot vs Monocot Root:

• Dicot → fewer xylem bundles, no pith or small
• Monocot → many bundles, large pith

Stem Anatomy

 Structure:

• Epidermis (cuticle present)
• Cortex (collenchyma + parenchyma)
• Endodermis (starch sheath)
• Pericycle
• Vascular bundles
• Pith

 Differences:

Feature	Dicot Stem	Monocot Stem
Vascular bundles	Ring	Scattered
Cambium	Present	Absent
Secondary growth	Yes	No

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Leaf Anatomy

 Structure:

1. Upper epidermis
2. Mesophyll
   • Palisade → photosynthesis
   • Spongy → gas exchange
3. Lower epidermis
4. Vascular bundles

 Types of Leaves:

• Dorsiventral (Dicot leaf)
  • Palisade on upper side
• Isobilateral (Monocot leaf)
  • Similar on both sides

 Secondary Growth (Important Concept)

• Increase in girth of plant
• Due to:
  • Vascular cambium → secondary xylem & phloem
  • Cork cambium → bark formation

👉 Seen mainly in dicots

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Key Concept: Structure–Function Relationship

• Thick walls → support (sclerenchyma)
• Thin walls → storage (parenchyma)
• Hollow tubes → transport (xylem/phloem)

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Complete Flowchart (Write in Exam)

Flowering Plant Anatomy
        ↓
Tissue Systems
        ↓
Epidermal | Ground | Vascular
        ↓
Organs
        ↓
Root → Absorption
Stem → Support + Transport
Leaf → Photosynthesis
        ↓
Special Features
        ↓
Secondary Growth (Dicots)

 Important Exam Points

• Casparian strip → controls water flow
• Cambium → responsible for secondary growth
• Xylem = dead tissue (mostly), Phloem = living
• Monocot vs dicot differences → very important