Modifications of root

a. Storage roots

1.  Conical Root

These are cone like, broad at the base and gradually tapering towards the apex. Example: Daucus carota.

2.  Fusiform root

These roots are swollen in the middle and tapering towards both ends. Example: Raphanus sativus

3.  Napiform root

It is very broad and suddenly tapers like a tail at the apex. Example: Beta vulgaris

b. Breathing root

Some mangrove plants like Avicennia, Rhizophora, Bruguiera develop special kinds of roots (Negatively geotropic) for respiration because the soil becomes saturated with water and aeration is very poor. They have a large number of breathing pores or pneumatophores for exchange of gases.

II. Adventitious root modification

a. Storage roots

1.  Tuberous root

These roots are swollen without any definite shape. Tuberous roots are produced singly and not in clusters. Example: Ipomoea batatas.

2.  Fasciculated root

These roots are in cluster from the base of the stem Example: Dahlia, Asparagus, Ruellia.

3.  Nodulose root

In this type of roots swelling occurs only near the tips. Example: Maranta (arrow root) Curcuma amada (mango ginger), Curcuma longa (turmeric)

4.  Moniliform or Beaded root

These roots swell at frequent intervals giving them a beaded appearance. Example: Vitis, Portulaca, Momordica, Basella (Indian spinach).

5.  Annulated root

These roots have a series of ring- like swelling on their surface at regular intervals. Example: Psychotria (Ipecac)

b.  Mechanical support

1.  Prop (Pillar) root

These roots grow vertically downward from the lateral branches into the soil.

Example: Ficus benghalensis (banyan tree), Indian rubber.

2.  Stilt (Brace) root

These are thick roots growing obliquely from the basal nodes of the main stem. These provide mechanical support.

Example: Saccharum officinarum, Zeamays, Pandanus, Rhizophora.

3.  Climbing (clasping or clinging) roots

These roots are produced from the nodes of the stem which attach themselves to the support and help in climbing. To ensure a foothold on the support they secrete a sticky juice which dries up in air, attaching the roots to the support. Example: Epipremnum pinnatum, Piper betel, Ficus pumila.

4.  Buttress root

In certain trees broad plank like outgrowths develop towards the base all around the trunk. They grow obliquely downwards and give support to huge trunks of trees. This is an adaptation for tall rain forest trees. Example: Bombax ceiba (Red silk cotton tree), Ceiba pentandra (white silk cotton tree), Terminalia arjuna, Delonix regia, Pterygota alata.

c.  Vital functions

1.  Epiphytic or velamen root

Some epiphytic orchids develop a special kind of aerial roots which hang freely in the air. These roots develop a spongy tissue called velamen which helps in absorption of moisture from the surrounding air. Example: Vanda, Dendrobium, Aerides.

2.  Foliar root

Roots are produced from the veins or lamina of the leaf for the formation of new plant. Example: Bryophyllum, Begonia, Zamioculcas.

3.  Sucking or Haustorial roots

These roots are found in parasitic plants. Parasites develop adventitious roots from stem which penetrate into the tissue of the host plant and suck nutrients.

Example: Cuscuta (dodder), Cassytha, Orobanche (broomrape), Viscum (mistletoe), Dendrophthoe.

4.  Photosynthetic or assimilatory roots

Roots of some climbing or epiphytic plants develop chlorophyll and turn green which help in photosynthesis. Example: Tinospora, Trapa natans (water chestnut), Taeniophyllum.