Modifications of Roots

Tap roots and adventitious roots can get modified into a variety of forms to perform various functions.

Tap roots become fleshy for storage of food.

Conical: Base is broad and tapers gradually towards apex; Example - carrot
Fusiform: Swollen in middle, tapering toward both ends; Example - radish
Napiform: Spherical at base tapering sharply towards the tip; Example - turnip, beetroot
Tuberous: Thick and fleshy with no definite shape; Example: Mirabilis jalapa (4 O’clock plant)

Adventitious roots get modified for various functions.

Modifications for food storage

1. Tuberous: Swollen roots developing from nodes of prostrate stem. Example: Sweet Potato
2. Fasciculated Swollen roots developing in a cluster from the stem. Example: Dahlia
3. Nodulose: Only apices of roots become swollen like single beads. Example: Mango-ginger
4. Moniliform: Roots alternately swollen and constricted presenting a beaded or moniliform appearance. Example: Grasses, Sedges
5. Annulated: Looks as if formed by a number of discs placed one above the other. Example: Ipecac

Modification for photosynthesis

Assimillatory roots: Roots which when exposed to sun develop chlorophyll, turn green and manufacture food. Example: Tinospora

Modification for absorbing atmospheric moisture

Epiphytic roots: Aerial roots of epiphytes are greenish and covered with spongy tissue (Velamen) with which they absorb atmospheric moisture. Example: orchids

Modification for better gaseous exchange

Pneumatophores or respiratory roots: Some roots grow vertically up (negatively geotropic) into air. Exposed root tips possess minute pores through which roots respire, appear like conical spikes coming out of water. Example: Mangroves

Modification for sucking nutrition from host

Sucking roots or haustoria: Parasitic plants give out sucking roots or haustoria which penetrate living host plant and suck food from phloem. Example: Cuscuta

Modification for strong support

1. Prop roots: Roots develop from tree branches, hang downwards and ultimately penetrate the ground, thus provide support to heavy branches. Example: Banyan
2. Stilt roots: Extra roots developing from nodes, near the base of stem, grow obliquely downwards and penetrate the soil giving strong anchorage. Example: Sugarcane, Screwpine
3. Climbing roots: Weak climbers twine around and clasp the support with the help of climbing roots arising from their nodes, Example: money plant, betel
4. Clinging roots: Special clinging roots arise, enter the crevices of support and fix the epiphyte. Example: epiphytes, orchids

Modification for buoyancy and respiration

Floating roots: Spongy, floating roots filled with air, arise from nodes of some aquatic plants, and help in floating and respiration. Example: Jussiaea