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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