Roots are the principal water-absorbing
organs of a plant.
Roots can also be aerial or aerating
(growing up above the ground or
especially above water)
To absorb or take in water and minerals
from the ground
To hold the plant in place.
To store food for the plant
) Prop roots:
Prop roots grow from the stem to the
ground. They give extra support to the
b) Buttress roots:
Buttress roots are large roots on all sides of a
tall or shallowly rooted tree. Typically they
are found in rain forests where soils are poor
so roots don't go deep. They prevent the
tree from falling over and help gather more
nutrients. They are there to anchor the tree
and soak minerals and nutrients from the
ground, a function that would prove
difficult if the tree was unsoundly rooted.
Aerial roots are roots above the ground. They are
almost always adventitious. They can absorb water
from the air.They are also used to hold on to their
support. They are found in diverse plant
species, including epiphytes also known as air
plants, which includes the orchids, tropical coastal
swamp trees such as mangroves.
Clasping roots grow from the nodes of the soft
stem to cling on to other plants
Storage roots are swollen with nutrients and water
to prepare for unfavourable conditions. Some are
swollen main roots. Examples: carrot. Others are
swollen branched roots or adventitious.
Some plants in swampy areas have branch roots
that grow upwards, through the mud and into the
air. The exposed parts of the roots are spongy and
they take in air for respiration.
Some plants live on other plants and get food
materials from their hosts. Parasitic roots are used to
absorb food materials form their hosts.
Aerial root: Aerial roots are adventitious roots
formed on above the ground surface of the
earth or water. They function as prop roots or
E.g. Epiphytes (orchids), mangroves, banyan tree
(Ficus benghalensis), ivy (Hedera helix) etc.
Buttress root: Buttress roots are form of prop
root that develop board like growth on the
upper side of the tree and assist with support of
the trunk against lateral forces. It serves as
effective tension members to prevent
uprooting. Many tropical tress are buttress roots
e.g. Ceiba pentandra
Contractile roots: Contractile roots is a
specialized thickened root and it serves
to pull down a rhizome, bulb, corn, etc.,
to an appropriate level in the soil e.g.
Crocus, Allium species
Fibrous roots: Fibrous root is a specialized
root system in which both primary and
lateral roots are divided with equal
diameters. Most of the monocots are
fibrous roots consisting of an extensive
massive of similar size of roots e.g.
Coconut palm, Trifolium repens, grass
Fleshy roots: Fleshy roots store nutrient
reserves in the fleshy roots. Their roots are
larger in diameter and soft to the touch
E.g. Beta vulgaris, carrot
Haustorial roots: It penetrates into the
host tissues for nutrient absorption. Plants
with haustorial roots have a tendency to
suck the life out of plants around them.
e.g. Viscum album, Cuscuta, Rafflesia
Pneumatophorous roots: Pneumatophorous
roots contains spongy aerenchyma tissues
of plants living in swampy soils
Still roots: Still roots are adventitious support
roots (mangroves). They grown from lateral
branches, branching in the soil surface
Tuberous roots: These types of roots are
thick, soft and round in shape and they
contain more storage tissue than most
roots. e.g. Sweet potatoes
Taproot: A taproot is a primary root that
grows downward into the ground. From
main root it creates a central root from
which others develop. e.g. dandelions,
radishes, and carrots.
Internal Structure of the Root of a Typical Dicotyledonous
a) Epidermis: Outer layer of cells ("skin"). Protection.
b) Root Hair: An extension of specialized root epidermal
cells increasing surface area for absorption of water &
c) Cortex: Region between epidermis & vascular cylinder.
Supports plant parts & stores food.
d) Endodermis: Layer of cells just outside vascular
e)Pericycle: Cylindrical layer of cells inside endodermis.
Origin of cork & secondary (side) roots.
f) Vascular Cylinder: Arrangement of vascular
tissues as a central cylinder in roots. This is
shown as the large circular area in the middle of
g) Xylem: Living (outer) vascular system
carrying water & minerals throughout plant.
h) Phloem: Living (inner) vascular system
carrying dissolved sugars and organic
compounds throughout plant.
a) Root Hairs: Outward extensions of
epicermal cells which extend
between soil particles to collect
water and solutes (minerals).
Region of Maturation: Older
section of root tip where the root
begins adding cells to increase
the width, and where root hairs
b) Region of Maturation: Older section of root tip
where the root begins adding cells to increase
the width, and where root hairs form.
c) Region of Elongation: Region of root tip where
cells get longer, thus lengthening the root. This is
the only place where the root grows longer.
d) Region of Rapid Growth: Region where cells
divide rapidly by mitosis.
e) Apical Meristem: Cells near the tip that can
divide by mitosis to make any type of plant cell.
f)Root Cap: Dome-shaped mass of cells at the tip
which protect the meristem cells from damage
(as root extends through soil).
of Root Systems
› Taproot System
has prominent primary root
› Fibrous (diffuse) System
Primary root is lost and replaced by numerous
adventitious roots arising from the lower
portion of the stem
Slender in form and are more or less equally
Tap root system
Tap root is common in
dicots; the first or primary
root grows straight down
and remains dominant root
of a plant; often fleshy and
adapted to store food
(e.g., carrots, beets)
Fibrous root system
The fibrous root system of
monocots is a mass of
slender roots and lateral
branches that hold the
plant secure in the soil.