Biology Today — January 2018

(Jacob Rumans) #1

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
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

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