4. Plant Morphology_akar Ok(1)

7/29/2019 4. Plant Morphology_akar Ok(1)

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PLANTMORPHOLOGY

1. LEAF

2. STEM

3. ROOT


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ROOT General Characters:1. Roots are non green,

underground, (+) geotropic, () phototropic and (+)

hydrotropic.

2. Roots do not bear buds.

3. Roots do not bear nodes and

internodes.

4. Roots have unicellular root

hairs.


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1.Tap Root System(radix primaria/akar tunggang)

It develops from radicle and

made up of one main branch

and other sub branches. Theprimary roots and its

branches constitute tap root

system. e.x. Dicot roots.

TYPES OF ROOTS


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2. Fibrous Root System

In monocotyledonous plants,

the primary root is short lived

and is replaced by a large

number of roots.

These roots originate from the

base of the stem andconstitute

the fibrous root system, as seen in

the wheat plant.

Ex. Oriza sativa, Zea mays

TYPES OF ROOTS

Fibrous Root


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3. Adventitious root (radix adventicia)

In some plants, after sometime

ofthe growth of tap root

which arises from radicle stops

and then roots develop from

other part of plant, which are

branched or unbranched,

fibrous or storage, are knownas adventitious roots and

constitute fibrous root system

TYPES OF ROOTS

Adventitious Root


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The main functions of theroot

system are absorption of water

and minerals from the soil,

providing a proper anchorage

to the plant parts, storing

reserve food material and

synthesis of plant growthregulators.

Functions of Roots


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Morphologically four distinctregions are present in roots:1. Root cap (calyptra/tudung akar)

It is terminal structure. Itprotects tender apex of root.

2. Meristematic zoneCells of this regions are very smalland thin walled. They divide

repeatedly andincrease cellnumber3. Elongation region

The cells proximal tomeristematic zone undergo rapid

elongation and enlargementand are responsible for rapidGrowth of roots.

REGIONS OF ROOTS


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4. Maturation region

Cells proximal to region of

elongation gradually

differentiate and mature. Root

hairs are present in maturation

zone.

5. Root hairs

These root hairs absorb

water and minerals from the

soil.


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Roots in some plants change

their shape and structure and

become modified to

perform functions other than

absorption and conduction of

water and minerals. TheyAre modified for support

storage of food and respiration.

MODIFICATION OF

ROOTS


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1. Modified tap root for storagea.Fusiform roots (fusiformis/akar

tombak/akar pena)

These root are thicker in themiddle and tappered (meruncing)on both ends. In this type ofroots both hypocotyl and root

help in storage of food. eg.Radish.b.Conical rootsThese roots are thicker at their

upper side and tapering(meruncing) at basal end. eg.Carrot.

MODIFICATION OF

ROOTS


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c. Napiform (akar gasing)These roots become swollenand spherical at upper end and

tappered like a thread at theirlower end. eg. Turnip (Brassicarapa), Sugarbeet, Pachirizuserosus

d.Tuberous rootSuch roots do not have regularshape and get swollen & fleshy

at any portion of roots.eg. Mirabilis.


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Pachirizus erosus

Sugarbeet

Mirabilis


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2. Nodulated rootNodules are formed on branches ofroots by nitrogen fixing bacteria,(Rhizobium). eg. Plants of

leguminosae family (Papilionatae)

Pea.

3. Respiratory rootsHalophyte or mangrove grow in

oxygen deficient marshy area. Somebranches of tap root in these plantgrow vertically & comes out from soil.These roots are calledneumatophores through which airentered inside the plant. eg.Rhizophora, Heritiera, Sonaratia andother mangrove plant.


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4. Modification of adventitious

roots

a. Storage adventitious roots

Tuberous root : When foodis stored in these roots, theybecome swollen and form abunch. eg. Sweet potato(Ipomea batatas)

Fasciculated

Roots arise inbunch (cluster) from lowernode of the stem andbecome fleshy eg. Dahlia,Asparagus. Nodulose : In this type, tips

of roots swell up. eg.Curcuma zeodaria.


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Curcuma zedoaria


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Curcuma kwangsiensis

Curcuma aromatica


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b. Stilt roots or brace roots :When root arises from lowernodes and enter in soil

obliquely, known as stilt rootseg. Maize, Sugarcane,Pandanus(screwpine)

c. Prop root or pillar roots :when root arises frombranches of plant and growsdownward towards soil. It

function as supporting stemfor the plant. eg. Banyan.

Stilt roots


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Zea mays (stilt root)

Banyan tree (prop root)


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d. Buttress rootSuch roots appear from thebasal part of stem and spread

in different directions in thesoil. eg.Ficus, Bombax ,Terminalia. It is a characteristicfeature of tropical rain forest.

e. Climbing rootsThese roots arise from nodesand helps the plant in

climbing. eg. Betel, Blackpepper

Buttress root


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f. Foliar roots or EpiphyllousrootsWhen roots arise from leaf

they are called as foliar roots.eg. Bryophyllum.

g. Sucking or haustorial roots or

Parasitic rootsIn parasitic plant roots enterin the stem of host plant toabsorbed nutrition from host.

eg.Dendrophthoe, Cuscuta,Viscum.

haustorial roots


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Bryophyllum

h i il


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h. Assimilatory rootsThe aerial roots ofTinosporaand submerged roots ofTrapa(Water chestnut) become greenand synthesize food.Podostemon also has greenassimilatory roots.

i. Hygroscopic roots : These arefound in epiphytes, specially inorchids and help in absorptionof moisture from theatmosphere using special tissue

called velamen. eg.Orchids,Banda

Trapa

Orchid


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6. Leaf roots

In Salvinia, one leaf of each

node modifies into root like

structure for balancing the

plant in water.

4. Plant Morphology_akar Ok(1)

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