Biology Today — January 2018

Haustoria or sucking

roots

They are parasitic and

absorb nourishment from

host plant, e.g., Cuscuta.

Epiphytic roots

Thick, irregular roots which

hang down in air. They do

not have root cap and root

hair but possess a covering

of dead spongy tissue

known as velamen that

absorbs water from moist

atmosphere, e.g., Vanda.

Climbing or Clinging roots

These are non-absorptive roots

found in climbers. They may

arise from nodes or internodes

or both. They attach to their

support firmly by forming claws,

swollen disc, etc., e.g., Hedera,

Pothos etc.

Floating roots

These roots store air, become inflated and

help the plant to float on water surface.

They also help in gaseous exchange

(respiratory in function), e.g., Jussiaea.

Assimilatory roots

Green photosynthetic roots develop from

stem nodes and become highly branched

to increase photosynthetic area, e.g., Trapa.

Modications of adventitious root

For storage of food

For vital functions

For mechanical support

Tuberous roots

These roots arise

from nodes of

stem and become

tuberous and

fleshy for storage

of food, e.g.,

lpomoea.

Fasciculated

roots

Tuberous roots

in clusters,

e.g., Dahlia,

Asparagus.

Moniliform

roots

Swollen at

regular intervals,

e.g., Momordica.

Annulated roots

Ring like outgrowths

or swellings occur

at regular intervals,

e.g., Psychotria.

Palmate roots

The fleshy roots

are thickened like

human palm and

possess finger

like outgrowths,

e.g., Orchis.

Tuberous root

Fasciculated

root

Palmate

root

Annulated

root

Nodulose

roots

Swollen at tips,

e.g., Curcuma

amada. Nodulose

root

Moniliform root

Prop roots

These are thick pillar-like roots

which grow vertically downwards

from horizontal stem branches,

e.g., Ficus benghalensis.

Prop root

Stilt roots

The roots develop obliquely from

basal nodes of stem, e.g., maize,

Sorghum, screwpine, etc.

Stilt root

Climbing root

Epiphytic root

Reproductive roots

Adventitious roots

develop buds that grow

into new plants under

favourable conditions,

e.g., Dahlia.

Reproductive

root

Floating root

Assimilatory root

Rootless plants

Not all flowering plants possess roots as an essential part. Many aquatic plants do not have roots as there is little requirement for

absorption of water and mineral salts, e.g., Wolffia, Utricularia, Ceratophyllum.

However, some aquatic plants develop roots for balancing as in Lemna, Pistia or for fixation as in Hydrilla.

MORPHOLOGY OF STEM

• Stem is an ascending part of the plant body that develops from the plumule of the embryo and is usually negatively geotropic
  and positively phototropic.

Haustoria root