Saturday, July 11, 2009



  • Nodes and internodes absent
  • Buds absent in roots

{present in sweet potato (Ipomea batata) and Indian rose wood (Dalbergia sisso also called as shisham)… These buds are called radical buds }

  • Root cap is a protective single layer

*** root cap is multiple layered in screwpine ( Pandanus )

*** it is absent in hydrophytes as such but present as root pockets

Actually, root cap in form of loose sheaths is called as root pockets

Eg. Pistia, Eichhornia, Lemna

  • Root hairs : elongations of some special epidermal cells called trichoblast cells (tricho in latin means hair, blast is used for parent cell, like fibroblast , erythroblast etc. )
  • Epidermis of root : rhizodermis (rhizo means roots)

  • Two types
  1. Tap root : root which arises from radical of seed. It is deep feeder and present in dicots(generally)
  2. Adventitious roots: made by any part other than radical eg. Stem, leaf etc. It is surface feeder and mostly present in monocots.

  • Primary root= elongation of radical
  • Secondary root = branches of primary root
  • Tertiary root = branches of secondary root
  • Rootlets = branches of tertiary root


Modifications of tap root

èFor storage

a) fusiform :

spindle shaped

eg. Radish (Raffanus sativus)

b) conical :

cone shaped

eg Carrot (Dauscus carota)

c) Tuberous:

eg 4’o clock plant (Mirabilis) \\ humorous common name naa??? I too laughed a lot at it when I had to study all these \\

d) Napiform:

Broad at one end, tapers at another end.

Eg: Turnip (Brassica rapa) eg2: Beet root (Beta vulgaris)

è Respiratory roots (pneumatophores): mangrove plants like Avicennia, Sonneritia

These help in gaseous exchange. And they are negatively (-ve) geotropic (anti gravitational movement. i.e move opposite to gravity )

è Nodulated roots

Rhizobium bacteria is present in the nodules

Eg. Legume plants.

Aerorhizobium present in Sesbania plant in which stem nodules are formed. In the same plant, rhizobium are also present in their root nodules.

Modifications of adventitious roots

è For storage

i) Tuberous

Eg. Sweet potato ( Ipomea batata)

ii) Fasciculated roots

*** Fascicula = group ( many group tubers present)

Eg Asparagus, Dahlia

iii) Palmate roots

*** Looks like palm of hand

Eg. Orchis

iv) Beaded roots ( monoliform roots)

*** swellings at regular intervals present

Eg. Vitis

v) Nodulose roots

*** swelling at one end of root

Eg. Mango ginger (Curcuma amanda)

v) Annulated roots

*** Ring like

Eg. Ipecac.

è for mechanical support

i) Prop roots

*** Pillar like

Eg. Banyan tree ( Ficus benghalensis) , Ficus genus in general

*** In banyan tree, these are hygroscopic in nature. It turns red on absorbing water

ii) Stilt roots / Brace roots

Originate from lower nodes of stem.

Obliquely enter the soil

Support complete stem

Eg. Jowar, Sugarcane etc. (most of the monocots)

iii) Butress roots / Plank roots

Originate from base of stem

Eg. Bamboo ( Bombax)

iv) Climbing roots

eg. Money plant (Pothos)

è Adventitious roots performing other special functions

i) Respiratory roots

Eg. Jussiaea

*** Not to be confused with pneumatophores which are modifications of tap root, but it too performs respiration.

ii) Assimilatory roots

*** Roots perform photosynthesis, make food.

Eg. Water chestnut (Trapa , also known as singhara in hindi)

Eg. Spring plant (Tinospora)

iii) Parasitic roots / Haustorial roots

Help in absorption of food and water from other plants

Haustoria enters vascular bundles of the host

Eg. Cuscuta

iv) Hygroscopic roots

Moisture absorbing roots

By help of dead hygroscopic tissue called velamen

Eg. Orchid

*** Velamen has multiple epidermis (usually, only single epidermal layer is present)

v) Nest roots

Nest à Modification of leaf

Humus rich soil present in nest.

Adventitious roots enter into nest called nest root

Absorption of water and minerals takes place

Eg. Dischidia rafflesiana

vi) Foliar roots

Developed from leaves

Eg Bigonia (for balancing)

è Buyashacka!!!!

i) Utricularia, Podostemon and epipogium have no roots

ii) Flowering roots are present in monotrapa

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