Root System

The root system is the underground part of the plant consisting of the root and its branches.

1.0Characteristics of the Root

(1) The root develops from the radicle of the seed.

(2) It is non-green.

(3) It grows towards the soil i.e., towards gravity (geotropic).

(4) It grows towards water (hydrotropic).

(5) It grows away from light.

(6) It does not bear nodes, internodes, leaves, flowers and fruits.

2.0Parts of Root

(i) Primary root: In a dicot seed, the radicle gives rise to the primary or the main root. It is cylindrical and grows deep into the soil.

(In monocot seeds, the primary root that develops from the radicle soon perishes and new roots are formed at the base of the stem).

(ii) Secondary root: Lateral (side) branches of the main root are called secondary roots.

(iii) Tertiary root: The branches of the secondary root are called tertiary roots.

(iv) Root cap: The tip of each root is covered by a root cap. The root cap protects the tissue beneath as they push their way downwards through the soil.

(v) Root hair: Roots are covered by a cluster of fine thread-like structures called root hairs. Root hairs help the plant absorb water and minerals from the soil.

3.0Types of Root System

On the basis of structure

Tap root system

In this system, a single root (primary root) comes out from the seed after germination. Many branches and sub-branches come out from this main root called lateral roots and spread out into the soil. Such roots are found in dicot plants.

Eg. Mango, Neem, Pine, Sheesham, Pea, Carrot, Radish, Turnip and Beetroot, balsam, rose, mustard etc. 

Fibrous Root System

Many plants do not have a main root. Instead they have a cluster of fine roots, which come out from the base of stem. These roots do not go down as deep in the soil as tap roots. It is found in monocot plants.

eg: Grasses, cereals (like maize, rice and wheat) bamboo, sugarcane and onion, Palms, banana etc. 

(2) On the basis of their origin 

(i) True roots develop from the radicle of the germinating seed e.g., pea, carrot etc.

(ii) Adventitious roots grow from the stem or leaves or other vegetative non root organs, e.g., banyan tree etc.

4.0Modifications of Root

(i) To store food: Sometimes taproots of some plants become fleshy, swollen in the various shapes and sizes for storage of food. E.g. Carrot, Radish, Turnip, sweet potato, sugarbeet, beetroot etc.

(ii) To support plant: Special roots develop from nodes and internodes to support the plant and to gain maximum sunlight. These aerial roots are of the following types:

(a) Prop roots: These roots grow vertically downward from the horizontal branches. They look like ropes or pillars and penetrate into the soil wherever they touch the ground. e.g. Banyan tree.

(b) Stilt roots: These are the adventitious roots which develop from the lower nodes of the plants having weak stem. They grow obliquely downwards like stilts. e.g. sugarcane, maize, screw pine.

(c) Climbing roots: These are the adventitious roots which develop from the nodes and sometimes even from the internodes of the weak stem. These roots penetrate the cracks and crevices of the walls or supports on which these plants grow. They enable the plant to climb up a support. e.g. Ivy, black pepper, betel and money plant.

(iii) Nitrogen fixing roots: Underground roots of leguminous plants fix atmospheric nitrogen with the help of symbiotic nitrogen fixing, Rhizobium bacteria in their root nodules. e.g. Beans, peas, grams etc. 

(iv) For breathing purpose: Sometimes in marshy areas roots develop as conical spikes which grow upward to take oxygen from surroundings and are called breathing roots or pneumatophores. They have lenticels (air pores which remain open always) for exchange of gases.

e.g. Rhizophora, mangrove plants.

(v) Parasitic roots: These are the adventitious roots, called suckers or haustoria which arise from the stem and penetrate into the tissues of the host plant and establish connection with xylem and phloem. They absorb water, mineral salts and organic food material from the host. e.g. Dodder plant (Cuscuta).

(vi) Assimilatory roots: These are the roots containing chloroplasts and they can manufacture food just like leaves. Such roots are called photosynthetic or assimilatory roots.

e.g. Tinospora, Trapa natans (water chestnut).

5.0Functions of Root

(i) Anchoring the plant: Roots help to anchor (fix) the plant firmly into the ground.

(ii) Absorption of water and nutrients from the soil: Plants absorb water and minerals from the soil which they use to manufacture food.

(iii) Preventing soil erosion: Roots help to bind the soil particles together, thereby preventing them from being carried away by water and wind.

(iv) Some modified roots store food.

(v) Some roots help in climbing, support etc.

6.0Related Questionnaire

1. What are aerial or epiphytic roots?

Ans. These roots are present in those plants which grow aerially on the host plant, e.g., orchids. They have hanging roots which draw moisture from the air through spongy tissue found on their tips.

2. Tap roots are present in –

Ans. Turnip

3. Fibrous roots are present in –

Ans. Grasses

7.0
Also Read