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TYPES OF ROOT SYSTEMS | RTU | BOTANY
Fundamental Characteristics of Roots | Tap, Fibrous and Adventitious Roots
🌱 TYPES OF ROOT SYSTEMS
(For B.Sc. Botany Major – Morphology of Angiosperms, RTU HOJAI)1️⃣ INTRODUCTION TO ROOT SYSTEM
It primarily performs:
Anchorage
Absorption of water & minerals
Conduction
Storage (in many plants)
Hormonal signaling
🌿 Fundamental Characteristics of Roots
Roots typically show:
1. Positive geotropism (grow towards gravity)
2. Negative phototropism (grow away from light)
3. Absence of nodes and internodes
4. Presence of root cap
5. Presence of root hairs
6. Endogenous branching
2️⃣ ROOT SYSTEM – CONCEPT
Based on origin and development, root systems are classified into:
- Tap Root System
- Fibrous Root System
- Adventitious Root System
3️⃣ TAP ROOT SYSTEM 🌳
A tap root system develops directly from the radicle of the embryo and continues to grow as the main dominant root.
The primary root remains prominent and produces secondary and tertiary branches.
🔹 Developmental Origin
Radicle → Primary Root → Secondary Roots → Tertiary Roots
It shows acropetal branching pattern.
One main thick root (Primary root)
Smaller lateral branches
Deep penetrating system
Mostly found in:
Dicotyledonous plants Gymnosperms
Examples:Mustard, Pea, Gram, Mango, Neem
✔ Strong anchorage
✔ Deep absorption of water
✔ Drought resistance
✔ Efficient nutrient uptake
Tap roots allow plants to:
Survive in dry conditions
Reach deeper water tables
Prevent soil erosion
🔹 Modification of Tap Root
| Type | Example |
|---|---|
| Conical | Carrot |
| Fusiform | Radish |
| Napiform | Turnip |
4️⃣ FIBROUS ROOT SYSTEM 🌾
In this system, the primary root is short-lived, and numerous roots of similar size arise from the base of the stem, forming a tuft.
Radicle → Short-lived
Stem base produces many thin roots
This results in a dense mat-like structure.
No dominant root
Roots of equal thickness
Shallow spreading system
Common in:
Monocotyledonous plants
Examples:
Wheat, Rice, Maize, Grass
✔ Rapid absorption of surface water
✔ Prevents soil erosion
✔ Ideal for loose soil
Fibrous roots are advantageous in:
Heavy rainfall areas
Soil conservation zones
Lawns and grasslands
They form a soil-binding network.
5️⃣ ADVENTITIOUS ROOT SYSTEM 🌴
Roots that arise from any plant part other than the radicle are called adventitious roots.
They may arise from:
Stem
Leaves
Nodes
Internodes
They are not part of the primary root axis.
They may replace the tap root system.
Found in:
1. Monocots
2. Some dicots
3. Vegetative propagation plants
Examples:
Banyan (Prop roots), Sugarcane (Stilt roots), Money plant, Sweet potato
Adventitious roots show remarkable specialization:
| Type | Function | Example |
|---|---|---|
| Prop roots | Support | Banyan |
| Stilt roots | Mechanical support | Maize |
| Pneumatophores | Respiration | Mangrove |
| Climbing roots | Climbing | Betel |
| Storage roots | Food storage | Sweet potato |
Adventitious roots:
1. Allow vegetative propagation
2. Enable environmental adaptation
3. Provide mechanical stability
6️⃣ COMPARATIVE ANALYSIS
| Feature | Tap Root | Fibrous Root | Adventitious Root |
|---|---|---|---|
| Origin | Radicle | Stem base (after radicle degeneration) | Any plant part except radicle |
| Dominant Root | Present | Absent | Absent |
| Depth | Deep | Shallow | Variable |
| Typical in | Dicots | Monocots | Both |
| Example: | Mustard | Wheat | Banyan |
7️⃣ ANATOMICAL DIFFERENCES (UNDERGRADUATE LEVEL)
1. Secondary growth common
2. Cambium present
3. Thickened vascular tissues
4. Fibrous Root
5. Usually no secondary growth
6. Many vascular bundles
7. Thin cortex
8️⃣ EVOLUTIONARY PERSPECTIVE
- Tap root system evolved in dicots for deep anchorage.
- Fibrous system evolved in monocots for rapid colonization.
- Adventitious roots demonstrate adaptive radiation.
9️⃣ EXAM-ORIENTED IMPORTANT POINTS
✔ Fibrous root replaces radicle
✔ Adventitious root originates from non-radicular parts
✔ Secondary growth prominent in tap roots
✔ Fibrous roots prevent soil erosion
🔟 DIAGRAM PRACTICE (ESSENTIAL)
Tap root system (labeled)
Fibrous root system
Prop root of Banyan
Pneumatophore
Label:
Primary root
Lateral roots
Root hairs
Stem base
1️⃣1️⃣ HIGHER ORDER THINKING QUESTIONS
- Why are tap roots advantageous in desert plants?
- Why are fibrous roots effective in preventing soil erosion?
- How do adventitious roots demonstrate ecological plasticity?
- Why is secondary growth common in tap roots but rare in fibrous roots?
1️⃣2️⃣ CONCEPTUAL SUMMARY (MEMORY MAP)
↓
Origin-based classification
↓
Tap → Radicle persists
Fibrous → Radicle dies
Adventitious → Non-radicle origin
↓
Function + Ecology + Evolution
