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Root System

NIOS · Class 12 · Biology

Quick revision notes for Root System — NIOS Class 12 Biology. Key concepts, formulas, and definitions for last-minute revision.

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Key Topics to Revise

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6.1 Characteristics of Roots

  • Roots are non-green because they lack chlorophyll – they grow underground away from light.
  • Roots do NOT have nodes and internodes (unlike stems).
  • Roots do NOT bear leaves or buds.
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6.2 Types of Root Systems

  • There are TWO main types of root systems: (1) Tap Root System and (2) Fibrous Root System.
  • TAP ROOT SYSTEM: Develops from the radicle. The primary (tap) root persists and gives off secondary and tertiary lateral roots. Found in DICOTS (e.g., gram, chinarose, neem, sunflower, mustard, carrot
  • FIBROUS ROOT SYSTEM: Primary root is short-lived. A cluster of slender, fibre-like roots arises from the base of the stem. Found in MONOCOTS (e.g., maize, grasses, wheat).
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6.3 Regions of Root (Root Apex)

  • The apical (tip) region of any root shows FOUR distinct zones, from tip to base.
  • ZONE 1 – ROOT CAP REGION: A thimble-shaped structure. Protects the delicate apical meristem (growing tip) from harsh soil particles. Constantly renewed as it wears out. In aquatic plants (Pistia, wate
  • ZONE 2 – REGION OF MERISTEMATIC CELLS (APICAL MERISTEM): Actively dividing cells. Consists of three layers: (a) Dermatogen – outermost; matures into epiblema and root cap; (b) Periblem – middle layer;
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6.4 Modifications of Roots

  • Roots undergo modifications to perform special functions beyond simple anchorage and absorption.
  • TAP ROOT MODIFICATIONS (for food storage – all become fleshy): (1) CONICAL – broad at base, tapers gradually to apex, e.g. Carrot; (2) FUSIFORM – swollen in middle, tapers at both ends, e.g. Radish; (
  • ADVENTITIOUS ROOT MODIFICATIONS FOR FOOD STORAGE: (1) Tuberous – from nodes of prostrate stem, e.g. Sweet Potato; (2) Fasciculated – cluster from stem base, e.g. Dahlia; (3) Nodulose – only apices swo

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Full Notes

Key Concepts

Roots possess unique identifying featuresRoot systems are categorized into twoRoots are classified as tap rootsThe apical region of every rootTap roots undergo modifications to store

Frequently Asked Questions

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Sources & Official References

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