Practical Exam Botany

Root

is a downward growth of the plant into the soil.

Functions of roots (1)

Roots fix the plant to the soil and give mechanical support to the plant body.

Functions of roots (2)

Roots absorb water and the minerals dissolved in it from the soil and transport them to the aerial parts where they are needed.

Functions of roots (3)

Root undergoes modification and per-forms special functions like storage, respiration, repro-duction, etc.

Parts of a Root

• Root Cap

• Region of Cell Division

• Region of elongation

• Region of Root Hair

• Region of Maturation

Root cap

protects the growing cells and as and when it is worn out it is replaced by the underlying tissues immediately.

Region of cell division

is the meristematic tissue producing new cells.

Region of elongation

The newly formed cells grow further by elongation resulting in an increase in the length of the root.

Region of root hairs

are responsible for strengthening the hold of roots into the soil and also for the absorption of water.

Region of maturation

It does not absorb anything, but is mainly responsible for the absorbed material by roots.

Types of roots

• Tap Root System

• Adventitious Roots

Tap root system

The radicle grows into the soil and forms main axis of the root known as tap root. It grows further to produce branches in the acropetal manner known as secondary roots which further branches to give tertiary roots.

Adventitious root

They may develop from root base nodes or internodes

Modification for storage of food (Tap Root)

• Conical

• Fusiform

• Napiform

Conical

cone-like, broader at the base and tape-ring at the tip.

Fusiform

roots are more or less spindle shaped.

Napiform

are spherical shaped and very sharply tapering at lower part.

Modification for storage of food (AdventitiousRoot)

• Tuberous roots

• Fasciculated tuberous roots

• Palmated tuberous roots

• Annulated roots

Tuberous roots

get swollen and form single or isolated tuberous roots which are fusiform in shape

Fasciculated tuberous roots

are several tuberous roots occur in a group or cluster at the base of a stem

Palmated tuberous roots

are exhibited like palm with fingers

Annulated roots

swollen portion is in the form of a series of rings

Modifications for support

• Clinging or Climbing roots

• Stilt roots

• Columnar roots

Clinging or Climbing roots

These types of roots are developed by plants like black pepper for support or for climbing purposes at nodes

Stilt roots

is observed in maize and screw-pine, which grow vertically or obliquely downwards and penetrate into soil and give addi-tional support to the main plant.

Columnar roots

support is given by specially developed pillars or columnar roots

Modifications for special functions

• Respiratory roots or pneumatophores

• Sucking roots or Haustoria

• Photosynthetic roots

• Epiphytic or Assimilatory roots

• Nodulated roots or root tubercles

Stem

consists of the axis and the leaves.

Weak stems

When the stems are thin and long, they are unable to stand erect

Types of weak stems

• Creepers or Prostate stem

• Climbers

• Twinners

Creepers or Prostate stem

When they grow flat on the ground with or without roots

Climbers

They climb on the support with the help of tendrils, hooks, prickles or roots

Twinners

These coil the support and grow further

Herbaceous and woody stems

normal stems and may be soft or hard and woody

Underground modifications of stems

• Rhizomes

• Tubers

• Bulb

• Corm

Rhizomes

are thick and are characterized by the presence of nodes, internodes and scale leaves

Tubers

are characterized by the presence of ‘eyes’ from the vegetative buds which grow further and develop into a new plant

Bulb

They are present in the axils of the scales, and few of them develop into new plants in the spring season at the expense of stored food material in the bulb.

Corms

They bear buds in the axil of the scaly leaves, and these buds then develop further to form a new plant.

Sub-aerial modifications of stems

• Runner

• Stolon

• Offset

• Sucker

Runner

These creep on the ground and root at the nodes.

Stolon

These are lateral branches arising from the base of the stems which grow horizontally.

Offset

These originate from the axil of the leaf as short, thick horizontal branches and also characterized by the presence of rosette type leaves and a cluster of roots at their bottom.

Sucker

They grow obliquely upwards, give rise to a shoot which develop further into a new plant.

Aerial modification of stems

• Phylloclades

• Thorns and prickles

• Stem tendrils

• Bulbils

Phylloclades

are characterized by the presence of small leaves or pointed spines

Thorns and prickles

they are superficial outgrowths.

Stem tendrils

the buds develop into tendrils for the purpose of support.

Bulbils

These are modifications of floral buds meant for vegetative propagation

Leaves

are flat, thin green, appendages to the stem, containing, supporting, and conducting strands in their structure.

Parts of a Typical angiospermic leaf

• Leaf Base or Hypopodium

• Petiole or Mesopodium

• Lamina or Leaf Blade or Epipodium

• Stipules

Leaf Base or Hypopodium

it is attached to the stem.

Petiole or Mesopodium

It is the stalk of leaf with which leaf blade is attached to the stem

Lamina or Leaf blade or Epipodium

The flat expanded part of the leaf that may be thick as in xerophytic leaves or thin as in hydrophytes or intermediate as in mesophytes.

Stipules

These are the two small outgrowths found at the base of the leaf, to protect the axillary bud.

Shape of the lamina of leaves

• Acicular

• Subulate

• Linear

• Oblong

• Lanceolate

Acicular

Needlelike

Subulate

With acute apex and recurved point

Linear

When it is long, narrow and flat

Oblong

Broad leaves with two parallel margins and abruptly tapering apex.

Lanceolate

Which look like lance or spear shaped

Leaf margins

• Entire

• Sinuate or wavy

• Crenate

• Dentate

Entire

When it is even and smooths

Sinuate or wavy

With slight undulations

Crenate

When the teeth are round

Dentate

Toothed margin, teeth directing outwards

Leaf apices

• Obtuse

• Acute

• Acuminate

• Recurved

• Cuspidate

Obtuse

Rounded tip

Acute

When it is pointed to form acute angle, but not stiff

Acuminate

Pointed tip with much elongation

Recurved

When the apex is curved backward

Cuspidate

With spiny tip

Leaf bases

• Symmetrical

• Asymmetrical

• Decurrent

• Cordate

Leaf surface

• Glabrous

• Rough

• Hairy

Glabrous

When surface is smooth and free of hair or any outgrowth

Rough

When harsh to touch

Hairy

When covered with hairs

Types of leaves

• Simple leaves

• Compound leaves

Simple leaves

A leaf which has only one leaf blade or lamina

Compound leaves

consists of more than one leaf blade or the lamina

Decompound leaf

Wherein compound leaf is much divided irregularly

Classifications of Compound Leaves

• Pinnate compound leaves

• Unipinnate compound leaves

• Bipinnate compound leaves

• Tripinnate compound leaves

Classifications of Decompound Leaves

• Palmate compound leaves

• Unifoliate compound leaf

• Trifoliate compound leaf

• Multifoliate compound leaf

Venation

The arrangement of veins in the lamina or leaf blade

Two types of Venation

• Reticulate venation

  • Unicostate-reticulate

  • Multicostate-reticulate

• Parallel venation

  • Unicostate-parallel

  • Multicostate-parallel

1. Reticulate venation

is characterized by the fact that many veins and veinlets in the lamina of the leaf are arranged in the form of network or reticulars.

Unicostate-reticulate venation

the leaf contains only one midrib and several veins are given out on both the sides to form the network

Multicostate-reticulate venation

many veins of equal strength arise from the end of the petiole.

2. Parallel venation

the vein and veinlets in leaf blade are arranged parallel to one another

Unicostate parallel venation

leaf consists of only one midrib running from apex to the petiole of the leaf.

Multicostate parallel venation

many number of main veins of equal strength arise from the tip or the petiole and run parallel to each other.

Phyllotaxy

mode of arrangement of leaves on the stem

Types of Phyllotaxy

• Alternate or spiral

• Opposite

  • Opposite decussate

  • Opposite superposed

• Whorled

• Leaf mosaic

Alternate or spiral

characterized by the presence of one leaf at each node and all leaves together make a spiral path on the axis

Opposite

When two leaves are placed at the same node and are opposite to one another

Opposite decussate

one node is at right angles to the pair of leaves at the next node

Opposite superposed

one pair of leaves is placed above the other exactly in the same plane

Whorled

When more than two leaves are present in a single node and are arranged in a circle

Leaf mosaic

the leaves are so arranged that there will not be any overshading and all the leaves are exposed properly.

Modifications of Leaves

• Leaf tendrils

• Leaf spines

• Phyllode

• Scale Leaves

• Pitcher and bladder