Leaf is flattened part . It arise from the node of the stem, leaf have rich Amount of chlorophyll.

LEAF

Histology of leaf means , studying about internal parts of leaf.

A) Dorsiventral leaf

CUTICLE

UPPER EPIDERMIS

PALISADE CELL

VACULAR BUNDIE

GUARD CELLS

LOWER EPIDERMIS

STOMA

SPONGY PARENCHYMA

A DORSIVENTRAL LEAF

It is a characteristic of most dicot plants. The internal structure of such leaf is quite different on upper and lower surfaces because upper(dorsal) surface receives more sunlight in comparison to lower(ventral)surface. So dorsal surface is usually dark green and shiny. while ventral surface remains dull and light green.

In vertical section of dorsiventral leaf shows the following structure:

UPPER EPIDERMISLOWER EPIDERMIS

MESOPHYLLVASCULAR BUNDILES

UPPER EPIDERMIS

UPPER EPIDERMIS

It is single composed of closely fitted rectangular parenchymatous Cells.

Outer wall of the cells are cutinised to form as cuticle.

Usually stoma are absent on the upper epidermis.

Cuticle prevents the excessive transpiration

LOWER EPIDERMIS

LOWER EPIDERMIS

It is a single layer parenchymatous cells with

thin cuticle.

it contains large number of stomata.

Each stoma surrounded by two guard

Cells.

It helps in the exchange of gases between

atmosphere and plant.

The excess water is also evaporated

Through lower epidermis

MESOPHYLLThe tissue in between

upper and lower epidermis is known as mesophyll.

it is divided into two parta)Palisade parenchyma

b)Spongy parenchyma

a)Palisade parenchyma

It consists of one to three layers of

elongated,

Closely fitted cylindrical cells, immediately

after upper epidermis. The cells contains

chloroplast and perform photosynthesis. They

have intercellular spaces between them.

Palisade parenchyma

Cylindrical cell

Inter cellular spaces

b)Spongy parenchyma

It is present between palisade tissue and

lower epidermis and composed of loosely arranged

rounded irregular parenchymatous cells with

intercellular spaces. This cells contain few

chloroplast and take part in manufacture of food.

The main function

Of spongy parenchyma is exchange gases through

intercellular spaces.

VASCULAR BUNDLESVascular bundles are present in between palisade and

spongy tissue. Each vascular bundle consist of xylem towards upper Epidermis and phloem towards lower. Surrounding each vascular bundle, there is present a bundle-sheath composed of thin walled cells.

it conducts water and minerals to various parts of lamina. xylem parenchyma store food. Phloem parenchyma is responsible for transpiration of food material

Vascular bundles are conjoint, and collateral and closed type.

B) ISOBILATERAL LEAF

B) ISOBILATERAL LEAF It is usually present in monocots. both surface of leaf receives more or less equal exposure to sunlight. internal structure is uniform on both surfaces

A vertical section of maize leaf shows the

following structure

Epidermis

mesophyll

Vascular bundles

EPIDERMISThere is an upper and lower layer of

epidermis .both the epidermis are single layered, consists of compactly arranged oval cells. Outer walls of these epidermis possess cuticle and stomata. The stomata help in exchange of gases. Some cells of upper epidermis become large and vacuolated and called bulliform or motor cells

MESOPHYLLIt consists of thin walled spherical cells

with small intercellular spaces. The mesophyll cells are not differentiated into palisade and spongy parenchyma. The cells contain chloroplast and perform photosynthesis.

VASULAR BUNDLESNumber of large and small vascular bundles

are present in the mesophyll at equal distance. Each bundle is surrounded by a thin walled bundle sheath.The vascular bundles are conjoint, collateral and closed.the xylem is present towards upper surface and phloem towards lower surface of the leaf.

DORSIVENTRAL LEAF

1 Dorsiventral leaf is dicot.

2 Stomata present on lower

epidermis, hence hypotomatic.

3 MesophyII cell are differentiated

Into palisade and spongy parenchyma,

4 Bulliform cells are absent in the

epidermis

5 Netted venation.

6 Usually upper surface is dark

Green in colour than lower surface.

ISOBILATRIAL LEAF

1 Isobilateral leaf is monocot.

2 Stomata present on both upper and

lower epidermis, hence amphistomatic.

3 Mesophyll cells consist of only

spongy prenchyma which are small thin

walled cells with small intercellular spaces

4 Upper epidermis contains bulliform

Cells.

5 parallel venation.

6 Upper and lower surfaces are

equally green