Biology Today — January 2018

(Jacob Rumans) #1
Zone of differentiation/maturation
Cells in this region are differentiated into permanent
tissues (viz. xylem, phloem, pericycle, endodermis,
cortex, etc.) depending upon the functions they have
to perform. Root hairs are also present in this zone,
which help in water absorption.
Function : Increase the exposed surface of the root
for absorption.

Zone of cell elongation
It is present behind the meristematic zone. Cells of this
region have lost the power of division and elongate
rapidly thus, increasing the length of the root.
Function: External cells are responsible for
absorption of water and mineral salts from the soil.
Zone of cell formation or meristematic zone
It is subterminal in position and lies below the root
cap. It consists of compactly arranged small, thin
walled, isodiametric and meristematic cells having
dense protoplasm that are in active state of division.
Function : Produces new cells for root cap
and is essential for growth of root.

Zone of mature cells
Forms the bulk of root and consists of thick walled,
impermeable cells that do not undergo any change,
hence does not help in water absorption.
Function : Gives rise to lateral roots and anchors
the plant firmly in the soil.

Root cap
Cap-like parenchymatous, multicellular structure
which covers the root meristem. Its cells secrete
mucilage which lubricates the passage of root
through soil. These cells also possess starch
grains which take part in graviperception.
Function : It protects the root meristem
from friction of soil particles.

Root hair
Increases the exposed surface of the root for
absorption. New root hair appears in older
part of the zone of elongation in order to
absorb water from newer parts of soil.

Fig.: Zones of a typical root

Types of Root System

  • There are three types of root system occurring in plants, i.e., tap root system, fibrous root system and adventitious root system.

Table: Comparison between different types of root system
Tap root system Fibrous root system Adventitious root system
(i) It is formed from the radicle of the

It occurs in place of tap root system at the
base of main stem.

It may develop from any part of the plant
other than radicle or its branches.
(ii) It is always underground. It is always underground. It may be underground or aerial.
(iii) It consists of a single primary (main)

Primary root is short lived. Instead
underground roots arise in groups from
base of stem.

Primary root is absent and it consists of
roots forming a cluster.

(iv) Primary root produces distinct
secondary roots, tertiary roots and
rootlets in acropetal succession.

The main roots are of equal lengths and
give off small branches. Main roots and
their branches are thin and thread like.

The roots may be thick, thin or variously

(v) It may be surface or deep feeder, the
deep feeder being the usual feature.

It is usually surface feeder. It is usually surface feeder.

(vi) It is commonly found in dicots. It is commonly found in monocots. It is found both in dicots and monocots.
Primary or tap root

Fig.: Tap root system


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