Biology Today — January 2018

Modications of Roots

• Roots are primarily meant for anchorage of plant
  and absorption of water and minerals from soil for
  their transport to the shoot system. However, roots
  undergo morphological modifications to perform
  various functions such as food storage, mechanical
  support, etc.


• Both tap roots and adventitious roots are variously
  modified to serve different functions.

Pneumatophores (Respiratory roots)

Upright breathing aerial roots which develop

at short intervals, found in plants growing in

mangroves or saline swamps, near the seashore,

e.g., Avicennia. These roots pick up oxygen for

perspiration of roots and give out excess of CO 2.

These bear lenticels near their tips, while their

remaining surface is covered by cork.

Fleshy tap roots

Tap roots become swollen and fleshy with stored food. Depending

upon shape, these are of following types:

Conical : Thicker on the upper end and tapering at the lower end,

e.g., Daucus carota (carrot).

Tuberous : Swollen and without any definite shape, e.g., Mirabilis.

Napiform : Much swollen and spherical at the upper end and

taper downward into a thread like structure, e.g., Brassica rapa

(turnip).

Fusiform : Swollen in the middle and tapering on both ends, e.g.,

Raphanus sativus (radish).

Modications of tap root

Nodulated (Tuberculate)

Root nodules (small or large irregular

swellings) are present on the roots

and their branches that enclose

millions of N 2 fixing bacteria which

help to perform biological N 2 -fixation,

e.g., leguminous plants.

Buttress roots

They are horizontal roots that arise jointly

from the bases of tap root and the trunk.

They provide extra support, e.g., peepal.

Functions of roots

Anchorage

Roots take part in fixation of plant and supports the shoot system.

Absorption of water and minerals

Roots absorb water and minerals from soil.

Prevention of soil erosion

Roots hold the soil particles firmly to prevent soil erosion.

Transport

Roots transport the absorbed water and minerals to aerial or shoot system.