Transcript Launch Activity

Makes it
Roots
Inorganic ions
& water
Plant cell
requirements
Oxygen
for respiration
Stomata
Organic nutrients
e.g. sugars for
respiration
Carbon dioxide
for photosynthesis
Stomata
Mammals – have faster chemical
reactions happening in cells. E.g. they
Have a faster rates of respiration and
As result need more O2 & glucose.
Plants – have slower rates of respiration
They will have very different transport
systems
Plant transport systems
XYLEM VESSELS
PHLOEM TISSUE
Moves water from Moves products of P
roots upwards
Process is called
TRANSPIRATION
Process is called
TRANSLOCATION
SOIL
ROOT HAIR CELLS
AREA of
HIGH Ψ
ROOTS
XYLEM
LEAVES
ATMOSPHERE
AREA of
LOW Ψ
The structure of a root
If water is to pass through to the
xylem in the stem, it must move
through several types of
cell/structures.
Tough epidermis
Root hairs
Cortex
Stele
Endodermis
Casparian strip
The structure of a root
ROOT HAIR
EPIDERMIS
ENDODERMIS
XYLEM
STELE
PERICYCLE
PHLOEM
CORTEX
Soil particle
Water particle
Gas
AREA of
HIGH Ψ
Water with
inorganic ions
How water
enters a plant
AREA of
LOW Ψ
Root hair: with
dissolved materials
of cell
RESULT: water
enters the root
hair
How water
enters a plant
Osmosis
AREA of
HIGH Ψ
AREA of
LOW Ψ
Osmosis
How water
enters a plant
AREA of
HIGH Ψ
AREA of
LOW Ψ
Osmosis
How water
enters a plant
AREA of
HIGH Ψ
AREA of
LOW Ψ
Osmosis
How water
enters a plant
AREA of
HIGH Ψ
AREA of
LOW Ψ
Xylem
The previous slide is simplistic………
Before water gets to into the xylem,
it must travel through the cortex and
into the central structure – the stele.
ROOT HAIR
EPIDERMIS
ENDODERMIS
XYLEM
STELE
PERICYCLE
PHLOEM
CORTEX
Water moves through roots in two ways:
1.APOPLAST PATHWAY
2.SYMPLAST PATHWAY
Water moves through roots in two ways:
APOPLAST
PATHWAY
SYMPLAST
PATHWAY
APOPLAST
PATHWAY
SYMPLAST
PATHWAY
Both are routes for water through the cortex to the
stele
Water moves from cell
to cell by passing along
cell walls
Water moves into cell
through vacuole/cytoplasm
and into next cell via
plasmadesmata
This route stops at the
ENDODERMIS
This route continues into
the stele and supplies
the xylem
The Endodermis has a
ring called the
CASPRIAN STRIP
This is made of a wax
called SUBERIN
This stops water moving
thu. the APway
Invovled in water transport
Vessel elements
Tracheids
Xylem tissue
Fibres
-elongated, lignified
-dead, act as support
Parenchyma cells
-Normal plant cells
-No P role
-Isodiametric
There are 4 types
of xylem vessels
Xylem vessels are
made up of dead
cells with thickened
cell walls - LIGNIN
There is no
movement between
vessels – hole are
filled with cellulose
Vessel element
Remains of old cell walls
Lignified cell walls
Lumen
XYLEM
VESSELS
TRACHEIDS
Both are tubes through which water moves up a plant
Open ends
Tapered ends
Dominant method
of water movement
in modern plants
Dominant method
of water movement
in PRIMITIVE
plants
Structure of a leaf
Upper
Epidermis
Cuticle
Palisade
cells
Spongy
Mesophyll
cells
Lower
Epidermis
Air
spaces
Guard cell
(stomata)
Vascular
tissue
Stomata
Guard
cell
Upper
Epidermis
Palisade
cells
Spongy
mesophyll
cells
Vascular tissue
Water moves up
the xylem vessel
Water leaves the
xylem vessel thru a
pit
Water moves from
cell to cell via
osmosis
Water leaves
SMcells, entering
the air space
Water vapour
diffuses out of
stomata
Often there is a
water potential
gradient btwn the
cells and the
atmosphere
This ensures rapid
water loss from
stomata
This loss is called
TRANSPIRATION
Environmental factors that increase the
rate of transpiration
Warm/hot
Windy
Dry
There is a high water potential
gradient between the environment and
the spongy mesophyll
Environmental factors that decrease
the rate of transpiration
Cold
Wet
Still
There is a low water potential gradient
between the environment and the
spongy mesophyll
Low hydrostatic
pressure
Water gets sucked up
due to the h’static
differences
If there is a large loss of
water from the SMcells
into the atmosphere, this
will reduce the
hydrostatic pressure from
the top of the xylem
High hydrostatic
pressure
Section of a
xylem vessel
COHESION: water
molecules are attracted to
each other
ADHESION: water
molecules are attracted to
the lignin in the xylem
vessels
ADHESION & COHESION ensures there is a constant stream
of water running through the xylem vessels AKA MASS FLOW
Some plants help transpiration
by increasing the water pressure
At the base of xylem vessel
This is done by
pumping solutes
into the xylem
in the root
ROOT PRESSURE
This is not a
dominant force in
transpiration
This is done via
ACTIVE
TRANSPORT
This increases the rate at which water
Flows into the xylem via osmosis
Water follows down
the WP gradient
Active pumping of
solutes into the xylem
Plant
cutting
Air tight
seal
Tube with a
scale
Water filled
tube
MEASURING THE RATE OF TRANSPIRATION
USING A POTOMETER
Select plant to be used
in the experiment.
Results can be graphed as
follows; rate of water transpired
(µm3 per second) against time.
Underwater, make a cut an
angular cut (33o), separating
the main plant from the
cutting you are using.
We are assuming, that the
rate of water uptake =
the rate of transpiration.
Keep the cutting
beneath the water level,
this ensures the
column of water in
the xylem is not broken.
Fill the potometer with
water,
being sure to introduce an
air bubble into the capillary
tube.
The plant can now be exposed
to different environmental
conditions and the rate of water
uptake can be measured.
Then place the whole
Potometer under water,
and carefully insert the top of
the cutting into the top of the
potometer – it is vital
all this is done underwater.
XEROPHYTES – plants adapted to low water conditions
E.G. Marram grass Ammophila arenaria
Rolled leaf
Leaf hairs
Waxy
cuticle
Sunken
stomata
All are structural adaptations to lowering the rate of
transpiration
What other adaptations have the following
species evolved to cope with water stress?
Opuntia
Sitka spruce
Phlomis italica
Euphorbia canariensis
See page 139