Roots are generally non-green and lack nodes, internodes, buds, and leaves.
The radicle of the embryo gives rise to the primary root.
Branches of the root are called lateral roots and arise endogenously (from the inner layers).
Roots usually grow towards the center of the earth (positive geotropism).
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Types of Root Systems
There are mainly two types of root systems in flowering plants:
1. Tap Root System
Found in dicot plants.
The radicle develops into the primary root, which persists and grows deep into the soil.
Secondary, tertiary, and further branches arise from the primary root.
Example: Mustard, Mango, Pea.
2. Fibrous Root System
Found in monocot plants.
The primary root is short-lived and is replaced by a cluster of fine, thread-like roots that arise from the base of the stem.
These roots spread horizontally and provide better anchorage.
Example: Wheat, Rice, Maize.
3. Adventitious Root System
Roots that arise from any part of the plant other than the radicle.
Common in monocots and some dicots.
Example: Banyan (prop roots), Maize (stilt roots), Sweet Potato (tuberous roots).
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Modifications of Roots
Besides their primary functions, roots also undergo modifications to perform special functions:
1. Storage Roots
Store food materials.
Types:
Conical (Carrot)
Fusiform (Radish)
Napiform (Turnip, Beetroot)
2. Respiratory Roots
In swampy or marshy plants, roots grow vertically upward and develop pneumatophores for gaseous exchange.
Example: Mangrove plants like Rhizophora.
3. Supportive Roots
Prop roots: Hang down from the branches and provide support (Banyan).
Stilt roots: Grow obliquely from the base of the stem for support (Maize, Sugarcane).
4. Other Modifications
Climbing roots (Betel, Ivy).
Epiphytic roots with velamen tissue for absorbing moisture (Orchid).
Photosynthetic roots (Tinospora).
Parasitic roots or haustoria (Cuscuta).
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Functions of the Root
Anchorage of the plant in soil.
Absorption of water and minerals.
Conduction of absorbed substances to the stem.
Storage of reserve food (in some plants).
Performing special functions like respiration, photosynthesis, and parasitism in modified forms.
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Quick Revision Points
Tap root → Dicot → Persistent primary root.
Fibrous root → Monocot → Cluster of roots from stem base.
Adventitious root → Arises from parts other than radicle.
Modified roots perform special roles beyond absorption and anchorage.
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✨ Conclusion:
The root is more than just an underground organ for absorption and anchorage. Its wide range of modifications shows how plants adapt to diverse habitats and functions. Studying the morphology of roots not only helps in understanding plant structure but also explains their ecological and economic importance.