The Root Types, Regions & Modifications - Biology Class 11 - NEET PDF Download

What are Roots?

Roots are the vital underground (usually) organs of vascular plants that originate from the radicle and perform several essential functions for the plant's growth, support and survival.

Functions of the Root System

• Absorption of water and minerals: Root hairs and epidermal cells take up water and inorganic ions from soil; these are conducted upwards through the xylem to stem and leaves.
• Anchorage and support: Roots fix the plant firmly in the soil, preventing dislodgement by wind and other forces.
• Storage of reserve food: Many roots become swollen to store carbohydrates and other reserves (for example, carrot, radish, sweet potato).
• Synthesis of growth regulators: Roots synthesise plant hormones (for example, cytokinins, gibberellins, abscisic acid) which regulate growth and development.

In most dicotyledonous plants the radicle elongates to form a single main or primary root. This primary root may bear lateral branches called lateral roots (secondary, tertiary etc.). In many monocots the primary root is short‑lived and replaced by many roots arising from the stem base.

Types of Roots

1. Tap root system

• Consists of a single, prominent primary root (the taproot) that grows downward and gives off lateral branches.
• Common in dicots (e.g., mustard, pea, carrot — carrot being a modified storage taproot).
  

2. Fibrous root system

• Primary root is short lived and is replaced by numerous adventitious roots arising from the stem base; these are roughly equal in size and form a mat-like system.
• Common in monocots (e.g., wheat, rice, grass).
  

3. Adventitious roots

• Roots that arise from organs other than the radicle (stem, leaf or old root parts).
• Examples: prop and aerial roots of banyan, aerial roots of Monstera, adventitious roots of sweet potato (storage), roots on stem nodes of grass.

Different types of roots : (a) Tap (b) Fibrous (c) Adventitious

Regions (Zones) of a Root

The regions of a root are longitudinal zones from the tip upwards that differ in cell activity, differentiation and function.

Regions of Root

1. Root Cap: The root cap is a thimble-like structure that covers the apex of the root. It protects the delicate tip of the root as it grows through the soil.

2. Meristematic Region: Located a few millimeters above the root cap, the meristematic region is where active cell division takes place. The cells in this region are small, thin-walled, and have dense protoplasm. They continuously divide, contributing to the growth of the root.

3. Region of Elongation: The cells proximal to the meristematic region undergo rapid elongation and enlargement, resulting in the elongation of the root in length. This region is called the region of elongation, and it is responsible for the primary growth of the root.

4. Region of Maturation: As the cells of the elongation zone continue to differentiate and mature, they form the region of maturation, which is proximal to the region of elongation. In this region, the cells differentiate into different types of root tissues and structures.

5. Root Hairs: Some of the epidermal cells in the region of maturation form root hairs, which are delicate, thread-like structures that protrude from the surface of the root. Root hairs have a large surface area and are responsible for absorbing water and minerals from the soil, playing a crucial role in nutrient uptake.

Modifications of Roots (Only in NEET)

Roots often become structurally modified to perform specialised functions such as storage, support, respiration, propagation and parasitism. Common modifications are listed below with examples.

1. Storage roots (tuberous and fleshy roots):

• Taproot storage: Carrot, radish, turnip, beet — swollen primary roots that store starch and other reserves.
• Adventitious/tuberous roots: Sweet potato (Ipomoea batatas), Dahlia — adventitious roots become enlarged and store food.

Storage Roots

2. Prop (adventitious) roots:

• Roots that develop from branches or stems and grow downwards to the soil to give extra support.
• Example: Banyan (Ficus benghalensis) produces numerous prop roots from branches that become supporting pillars.

Prop Roots : Banyan Tree

• Arise from lower stem nodes and enter the soil obliquely, giving additional mechanical support.
• Examples: Maize, sugarcane, many grasses.
  

4. Pneumatophores (respiratory roots):

• Specialised upward‑growing roots with lenticels that facilitate gaseous exchange in water‑logged or swampy soils.
• Typical examples: Avicennia and Sonneratia(mangrove plants) develop pneumatophores to obtain oxygen for root respiration.
  Pneumatophores

• Roots that contract longitudinally to pull the plant or bulb to a favourable depth in the soil.
• Examples: some bulbs and corms (like lily and certain tulip/onion species).

6. Aerial roots and climbing roots:

• Aerial roots absorb moisture and may help epiphytic growth: e.g., Monstera, orchids.
• Climbing/adhesive roots (e.g., ivy) attach the plant to vertical surfaces.

7. Parasitic/haustorial roots:

Certain parasitic plants develop specialised haustoria that penetrate host tissues and draw water and nutrients. Examples include root parasites such as Striga and Orobanche.

8. Root nodules (symbiotic nitrogen fixation):

In many legumes, root infection by Rhizobium leads to formation of nodules where atmospheric nitrogen (N₂) is fixed to ammonia for plant use.

Summary

• Roots are multifunctional organs: absorption, anchorage, storage, conduction and synthesis of growth regulators.
• Major types: taproot, fibrous and adventitious.
• Longitudinally roots are divided into root cap, meristematic, elongation and maturation zones where root hairs develop.
• Numerous modifications (storage, support, respiration, parasitism, nodulation) adapt roots to specialised functions and environments.