1. Plant cell requirements
Makes it
Roots
Organic nutrients
e.g. sugars for
respiration
Inorganic ions
& water
Plant cell
requirements
Carbon dioxide
for photosynthesis
Oxygen
for respiration
Stomata
Stomata

3. 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

4. Plant transport systems
XYLEM VESSELS
PHLOEM TISSUE
Moves products of P
Moves water from
roots upwards
Process is called
TRANSLOCATION
Process is called
TRANSPIRATION

5. SOIL
AREA of HIGH Ψ
ROOT HAIR CELLS
ROOTS
XYLEM
LEAVES
AREA of LOW Ψ
ATMOSPHERE

6. 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.
Endodermis
Tough epidermis
Cortex
Stele
Root hairs
Casparian strip

7. The structure of a root ROOT HAIR EPIDERMIS ENDODERMIS XYLEM STELE
PERICYCLE
PHLOEM
CORTEX

8. How water enters a plant RESULT: water enters the root hair
Soil particle
Water particle
Gas
AREA of LOW Ψ
Root hair: with dissolved materials of cell
AREA of HIGH Ψ
RESULT: water enters the root hair
Water with inorganic ions

9. How water enters a plant
Osmosis
AREA of HIGH Ψ
AREA of LOW Ψ

10. How water enters a plant
Osmosis
AREA of HIGH Ψ
AREA of LOW Ψ

11. How water enters a plant
Osmosis
AREA of HIGH Ψ
AREA of LOW Ψ

12. How water enters a plant
Osmosis
AREA of HIGH Ψ
AREA of LOW Ψ
Xylem

13. 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

14. Water moves through roots in two ways:
1.APOPLAST PATHWAY
2.SYMPLAST PATHWAY

15. Water moves through roots in two ways:
APOPLAST
PATHWAY
SYMPLAST
PATHWAY

16. 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

17. This stops water moving
The Endodermis has a
ring called the
CASPRIAN STRIP
This is made of a wax
called SUBERIN
This stops water moving
thu. the APway

18. 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

19. 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

20. Remains of old cell walls
Vessel element
Remains of old cell walls
Lignified cell walls
Lumen

21. 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

22. Structure of a leaf
Upper
Epidermis
Cuticle
Palisade
cells
Spongy
Mesophyll
cells
Air spaces
Lower
Epidermis
Guard cell
(stomata)
Vascular
tissue

23. Stomata
Guard
cell
Upper Epidermis
Palisade
cells
Spongy mesophyll
cells
Vascular tissue

24. 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

25. gradient btwn the cells and the atmosphere
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

26. 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

27. 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

28. If there is a large loss of
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

29. COHESION: water molecules are attracted to each other
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

30. ROOT PRESSURE This is done by pumping solutes into the xylem
in the root
Some plants help transpiration
by increasing the water pressure
At the base of xylem vessel
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

31. Water follows down
the WP gradient
Active pumping of
solutes into the xylem

32. MEASURING THE RATE OF TRANSPIRATION
Plant
cutting
Air tight
seal
Tube with a scale
Water filled tube
MEASURING THE RATE OF TRANSPIRATION
USING A POTOMETER

33. Results can be graphed as follows; rate of water transpired
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.
The plant can now be exposed
to different environmental
conditions and the rate of water
uptake can be measured.
Keep the cutting
beneath the water level,
this ensures the
column of water in
the xylem is not broken.
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.
Fill the potometer with water,
being sure to introduce an
air bubble into the capillary tube.

34. XEROPHYTES – plants adapted to low water conditions
E.G. Marram grass Ammophila arenaria

35. All are structural adaptations to lowering the rate of transpiration
Rolled leaf
Leaf hairs
Waxy
cuticle
Sunken
stomata
All are structural adaptations to lowering the rate of transpiration

37. What other adaptations have the following
species evolved to cope with water stress?
Opuntia
Sitka spruce
Phlomis italica
Euphorbia canariensis
See page 139