Root System
NIOS · Class 12 · Biology
Complete topic list for Root System in NIOS Class 12 Biology. Key concepts, sub-topics, and what to focus on for board exams.
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Topics in Root System
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.
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).
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;
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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