Download + Complex Tissues

+
Complex Tissues
! Complex
tissues are made up of two or
more cell types.
! Xylem - Chief conducting tissue for water
and minerals absorbed by the roots.
! Vessels - Made of vessel elements.
! Long tubes open at each end.
! Tracheids - Tapered at the ends with pits
that allow water passage between cells.
! Rays - Lateral conduction.
+
Complex Tissues - Xylem
! Tracheids
! Long, thin
cells with pointed ends that conduct
water vertically
! Line up in columns like pipes by overlapping
their tapered ends
! die when reach maturity
! Water conducted through tubes made up of
tracheid cell walls
! Wherever two ends join, small holes in the cell
wall called pits line up to allow water to flow from
one tracheid to another.
+
Complex Tissues - Xylem
! Pits
always occur
in pairs so that a
pair of pits lines
up on either side
of the middle
lamella, or center
layer, of the cell
wall.
+
Complex Tissues - Xylem
! Vessel
elements
! barrel-shaped cells with open ends that
conduct water vertically.
! line up end to end forming columns,
called vessels, that conduct water.
! Some
have completely open ends, while
others have narrow strips of cell wall
material that partially covers the ends
! Die
at maturity, like tracheids.
+
Complex Tissues - Xylem
! Ray
cells……….
! Long lived parenchyma
cells that extend laterally
like the spokes of a
wheel from the center of
a woody stem out
towards the exterior of
the stem
! alive at maturity
! Transport materials
horizontally from center
outward
+ Complex Tissues - Xylem
! Xylem
fibers –
! long, thin
sclerenchyma cells
that run parallel to the
vessel element
! Help strengthen and
support xylem
!  Xylem
parenchyma cells!  Living cells
!  Distributed among
tracheids and vessels
!  Store water and
nutrients
+ Complex Tissues - Phloem
! Phloem
brings sugar [glucose from
photosynthesis] from the leaves to all parts of the
plant body.
! Phloem
is a living tissue at maturity.
! Two
most common cell types…….
! Sieve Tube Elements - Large, cylindrical
! Sieve Plates – Porous/perforated region
! Companion Cells - Narrow, tapered
! Phloem
cells.
also contains rays, fibers, and parenchyma
+ Complex Tissues - Phloem
! Sieve
tube element! Long, straw-like cells that link end to end
to form sieve tubes
! Have lots of holes in the cell wall, forming
a perforated plate called a sieve plate that
allows the sugar solution to pass from one
cell to the next in the sieve tube
! Alive at maturity
! Have no nucleus of their own, rely on their
adjacent companion cell
+ Complex Tissues - Phloem
Companion cells…..
• Living, nucleated cells that occur adjacent to
sieve tube element
•Regulate the sieve tube elements and help them
maintain themselves.
Phloem ray cells…..
• extend laterally through stems allowing
horizontal transport of materials
• phloem and xylem rays form from the same cell –
similar in structure and function
+ Complex Tissue- Phloem
! Phloem
fibers…..
! Long, thin sclerenchyma cells that run
parallel to sieve-tube elements
! Help strengthen and support the
phloem
! Phloem
parenchyma cells…..
! Living parenchyma cells located
between sieve tubes
! Stores water and food
+ Dermal Tissues
! Dermal
tissues cover plant surfaces or
create barriers that protect the plant.
! There
are three tissue in the dermal
tissue system:
! Epidermis
! Endodermis
! Periderm
+
Dermal Tissue- Epidermis
! A
single layer of cells
that separates the
inside of the plant
from its environment.
! Made
mostly of
parenchyma-like cells
that are alive at
maturity.
+ Dermal System- Epidermis
! Three
primary functions of epidermis:
! Prevent
water loss
! Epidermal
cells secrete a waxy material
called cutin, which forms a waxy layer called
the cuticle on the outside of the plant.
! The cuticle provides water-proofing to the
plant tissues so that their water does not
evaporate into the air.
! Epidermal cells packed tightly together with
very little space between the cells to prevent
water evaporation.
+ Dermal System- Epidermis
! Protect
plant from fungi and other
attackers:
! The
waxy cuticle and closely spaced cells
prevent fungi, bacteria, and insects from
being able to access the plant tissues.
! The wax makes the cells harder to penetrate,
and the tightly packed cells prevent attackers
from slipping into the interior of the plant
through gaps between cells.
+ Dermal System- Epidermis
! Allow
plant to exchange materials with
the environment:
! Plants
do gas exchange with the atmosphere.
! Plants need to take carbon dioxide from the
air in order to do photosynthesis and they
release oxygen gas as waste.
! The cuticle stops water loss but also
prevents gas exchange.
! Plants use openings in the epidermis called
stomata for gas exchange.
! Guard cells open and close stomata as
needed.
+ Dermal System- Epidermis
! Plants
absorb water and minerals from
the soil.
! Roots absorb water and minerals from
the soil through their surface cells.
! Plants like orchids that grow up in the
trees produce aerial roots called
velamen. The peidermis of velamen is
several cells thick and modified so that
it’s very absorptive, allowing the plant to
capture water and minerals from the air.
+
Dermal System- Epidermis
+ Dermal System- Endodermis
! The
endodermis is a layer of cells
between the cortex and vascular tissue in
the roots, as well as some stems and leaves.
! Important
to the overall water balance of
plants because it helps regulate the uptake
of water from the soil and helps prevent the
loss of water from plants.
+ Dermal System- Periderm
! The
periderm is the outermost tissue in
woody plants, forming the outer bark.
! It
is composed of mostly cork cells and
parenchyma cells.
! The
cork cells of the periderm help protect
the stem.
! Layers of cork cells are produced by the cork
cambium.
+ Dermal System- Periderm
! The
cork cells produce a waxy substance
called suberin, which helps protect the stem
from water loss and attack from fungi and
other pests.
! Cork cells die at maturity.
! The
parenchyma cells of the periderm allow
gas exchange with the environment.
! The
cork cambium also produces clusters of
parenchyma cells, forming pockets of tissue
called lenticels.
+ Dermal System- Periderm
! The
parenchyma cells
aren’t waxed, so they
can still exchange
gasses like carbon
dioxide and oxygen
with the environment.
+
Complex Tissues
! Secretory
Cells and Tissue
! Secretory cells may function
individually or as part of a secretory
tissue.
! Flower nectar
! Citrus oils
! Glandular hair mucilage
! Latex
Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display