1. Xylem1. Xylem

For translocation of water For translocation of water

and minerals nutrients and minerals nutrients

Consists mainly of Consists mainly of

vessels, tracheids,vessels, tracheids, fibres, fibres,

parenchyma cells,parenchyma cells, and and

xylem ray cellsxylem ray cells

Occurs in association Occurs in association

with, and usually internal with, and usually internal

to, the phloemto, the phloem

Complex Tissues

A vascular bundle

sclerenchyma cells (fibers)

pit

end walls of vessel elements

pit

vessel elementstracheidscomplete perforations in end

walls of vessel elements

VesselsVessels

A continuous longitudinal tube A continuous longitudinal tube

composed of composed of vessel elementsvessel elements..

Vessel elements are joined end Vessel elements are joined end

to end forming the long tubeto end forming the long tube

The vessel elements are The vessel elements are

perforated at both ends ( with perforated at both ends ( with

either single/simple perforation either single/simple perforation

or several perforations)or several perforations)

Vessels elements are dead cells Vessels elements are dead cells

at maturity, with lignified at maturity, with lignified

secondary cell wallsecondary cell wall

Usually larger in diameter but Usually larger in diameter but

shorter than tracheids shorter than tracheids

Salix vessel

Unsur-unsur veselVessel elements

scalariform perforation plate simple perforation plate

TracheidsTracheidsSimilar to vessels, tracheids are Similar to vessels, tracheids are

dead cells at maturity, with thick dead cells at maturity, with thick

lignified secondary cell walllignified secondary cell wall

Each tracheary element tapers at Each tracheary element tapers at

both ends and arranged end to both ends and arranged end to

end with other tracheidsend with other tracheids

Without any perforations at the Without any perforations at the

ends, instead there are ends, instead there are pitpit pairs

whenever two tracheids touch

each other

Smaller in diameter but greater in

length than vessels

pit

The secondary cell walls show various types of thickening

spiral pitted

PitPit : :

the region in the cell the region in the cell

wall without any wall without any

secondary thickening, secondary thickening,

through which water through which water

moves from cell to cell.moves from cell to cell.

2. Floem

For translocation of

food materials

Composed of sieve

tubes, companion cells,

fibres, parenchyma

cells and phloem ray

cells

Phloem

Sieve tube

Like vessels, they are composed of

sieve tube elements that are

arranged end to end

Without any large perforation at the

cell ends. Instead, the end walls are

perforated by pores forming the

sieve plate. The pores allow

cytoplasmic strands movement

between cells.

Sieve tube elements are living cells,

but do not possess a nucleus at

maturity.

sieve plate

sieve tube element

Companion cell

A specialised parenchyma cells,

characterized by a dense

cytoplasm and a conspicuous

nucleus, and associated with a

sieve tube element.

The protoplast of the companion

cell is connected to that of the

sieve tube element by means of

plasmodesmata.

Companion cell helps regulate the

flow of food materials in the sieve

tube.

3. Epidermis

The outermost cells found on all young organs of

plants, the part that is exposed to the outside

environment.

The cells differentiate from the protoderm.

Functions to protect the underlying tissues from

excessive water loss, and from physical injury

and pathogen attack.

Normally consisting of a single layer but sometimes

several layers thick, e.g. epidermis of aerial roots of

orchids and leaf epidermis of certain species to

prevent from excessive water loss.

Mostly secrete a fatty complex called cutin on the

inner and outer wall, forming the protective layer

called cuticle

Wax can also be produced on the surface of the

cuticle

In the epidermis of leaves are

pores/openings called stomata.

Each stomatal pore is surrounded

by a pair of guard cells.

Glands may be found in the

epidermis for secretion of protective

substances or other compounds.

Some epidermal layer may produce

hairs, needle-like structures or

scale-like structures to help control

water loss or to protect from attack

by insects and other animals.

guard cell

4. Periderm

In woody plants, the periderm replaces the

epidermis.

Cork cells (phellem) are produced in stems and

roots through the activity of the cork cambium

(phellogen).

The cork cells are rectangular in shape and are

dead at maturity.

When the cork cells are still alive, the cytoplasm

secretes a fatty substance called suberin making

the cork cells become water proof and help to

protect tissues below the bark.

Periderm

phellem

phellogen

phelloderm

(cork cells)

(cork cambium)

(parenchyma)

Small elliptical pores, consisting of loosely packed cells

and without suberin, called lenticels, protrude from the

periderm surface. Lenticels are analogous to stomata

and use for gaseous exchange.

Lenticel

5. Secretory cells and tissues

Cells that secrete either waste products or useful

products such as hormones, nectar and perfumery

substances.

Formed from parenchyma cells and are found in

specific parts of the plant body.

Examples : secretory cell that produce nectar in

flowers, oil in Citrus, latex in Euphorbiaceae and

resin in Mangifera

Resin ducts in a stem tissue