Plant transport systems include xylem and phloem. Xylem transports water and minerals upwards from roots to shoots passively, using no energy. Phloem transports food such as sucrose horizontally throughout the plant using energy from ATP. Xylem vessels are located towards the edges of stems to resist bending forces, while located centrally in roots to withstand stretching. Transpiration is the evaporation of water from plant leaves, powered by the transpiration stream which replaces lost water. Transpiration cools plants and transports minerals upwards from roots.

2. TWO transport systems in plants:
 XYLEM
 transports water and mineral salts
 no need for energy as ATP
 made of dead cells
 PHLOEM
 transports food e.g. sucrose, amino acids
using ATP
 made of living cells

3. Vascular tissue
is composed of:
 Xylem
 Phloem

4. Note how the xylem & phloem
branch to enter the leaves

5. Where are the xylem and pholem?
In the Leaf
mid-rib
vein
xylem
phloem

6. Direction of flow

7. What causes
the upward
flow within
the xylem?
Mostly,
evaporation
of water by
the sun.

8. Translocation
 is the long-distance transport of food
materials within a plant
To growing regions to be
Glucose produced by used as energy for growth.
photosynthesis in leaf is
converted to sugars
(mainly sucrose) and
translocated to different
parts of the plant.
To storage organ (fruit)
to be stored mainly as
sugars. To storage organ
(tubers in roots)
To be stored
mainly as starch.

9. Section through
a stem.
Section through
a root.

10. Cambium: a region of growth

11. Let’s discover the reason for the
different positioning of the xylem
& phloem in the stem & root
STEM: at the side
ROOT: at the centre

12. Shoot sways in the wind. What prevents it
from snapping?

13. Stem must be flexible to bend
without snapping
Sways in
the wind
Anchors
the shoot.

14. Give a reason for the arrangement of
the vascular bundles in the stem.
phloem
xylem
The xylem and phloem are arranged in bundles
near the edge of the stem to resist compression
and bending forces.

15. Stem resists:
Bending forces

16. Give a reason for the arrangement of
the vascular tissue in the root.
phloem
xylem
The xylem and phloem in the centre of the root
to withstand stretching forces.

17. To show the site of sugar movement
in a plant
A complete ring of bark
(containing phloem tissue) was
removed from a woody stem.

18. Result:
 the removal of the phloem prevents
transport in the plant

19. Conclusion:
 phloem tissue is the site of sugar transport

20. To show the site of water movement
in a plant

21. To show the site of water movement
in a plant
 plant is left in
eosin (red dye) for
about one hour
 cross sections of
the stem and root
are cut out and
examined

22. Celery stalk
in eosin. After 24 h Note red
lines.

23. Celery stem under microscope
Xylem stains
red

24. ….. if left for
many days

25. Celery leaf
veins stain
red

26. Predict what would happen.
1 2
3
4

27. Predict what would happen.

28. Which parts become stained red with
eosin?

29. STEM ROOT

30. What is the
function of root
hairs?
Absorb water and
mineral ions.

31. How are root
hairs adapted
for
absorption?
1. are long and
provide a large
surface area
2. have a thin cell
wall

32. Question: [SEP, 2005]
Plants need mineral ions which they obtain from
soil. Explain how the uptake of mineral ions by
plants, may be inhibited in waterlogged soils. (3)
Ions are taken up by active transport.
Active transport needs energy from
respiration.
There is not enough oxygen for roots to
respire in waterlogged soils.

33. Uptake and transport of
water

34. A root hair cell has an extension

35. Learn to draw a root hair cell
nucleus
cytoplasm
cell membrane
cell wall

36. How does water from the soil end up
in the xylem?
The Uptake of Water
Up xylem
vessels to
plant
into xylem
across
Water from soil absorbed into across cortex vessels
phloem
root hair cell cells

37. Water moves by osmosis across the
root causing root pressure
H2O H2O

38. Transpiration:
is the loss of water vapour from the
surface of a plant

39. Water vapour is lost via open stomata

40. Transpiration stream:
the flow of water from root to leaves

41. Transport Of Water And Mineral Salts
Transport in the Xylem
There are three forces that move
the water upwards in the xylem:
a) Root pressure - a force that
pushes water up the xylem
(produced by the continuous
movement of water through the root
cells.
b) Capillary action - a force that
pushes water up the narrow xylem
vessels.
c) Transpirational pull - a force that
pulls water up the xylem (produced
by evaporation of water from the
leaves).

43. QUESTION: SEP, 2011
Describe the path taken by a
water molecule from the root
hair to the stomata in a leaf. (3)

44. Root hair absorbs water by osmosis.
Water moves across the root cortex by osmosis.
Water enters xylem and moves up towards
leaves, mostly due to evaporation.
Water evaporates into
air spaces between
spongy mesophyll cells
and diffuses out via
stomata.

45. Let’s study
transpiration in detail.

46. Transpiration:
is the loss of water vapour from the
surface of a plant

47. How can you show that water is actually
lost by transpiration & not another
chemical?
Leave for 1 hour. Test condensation by
a piece of blue cobalt
chloride paper.

48. Blue cobalt chloride paper becomes
pink

49. Apparatus to measure the rate of
transpiration: Potometer
Weight Water
potometer potometer
balance

50. Weight potometer
 A potted plant is well
watered.
 A plastic bag is
wrapped around the
pot to prevent water
loss from the soil.
 The apparatus is
weighed at intervals
and changes in weight
indicate water loss.

51. Suggest a control for this experiment.
CONTROL

52. To study the effect of wind speed on
the rate of transpiration
Which graph is for
highest fan speed?
C

53. A water potometer

54. A water potometer measures the rate
of water ABSORBED by the plant
 it is assumed that:
amount of water absorbed = water lost

55. A water potometer
Capillary tubing.
Ordinary glass
tubing.
Why is capillary tubing
used rather than
ordinary glass tubing?

56. A water potometer

57. Precautions

62. Four factors affecting transpiration
1. Light
2. Temperature
3. Humidity
4. Wind currents

63. Four factors affecting transpiration
1. Light
 stomata open in the light and so
more water is lost

64. Four factors affecting transpiration
2. Temperature
 as temperature increases, evaporation
increases
Water molecules move
faster.

65. 3. Humidity
 in dry air, the plant loses more water vapour
than in humid air

66. High humidity in air : less transpiration.
WHY?
A lot of water
vapour in air. Not
A lot of water much difference
vapour inside leaf in concentration

67. Four factors affecting transpiration
4. Wind currents
 moving air removes water vapour from
the leaf surfaces

68. QUESTION: SEP, 2011
Stomata allow transpiration to occur.
Explain why if a plant is enclosed in a
transparent bag, the rate of transpiration
decreases. (4)
Air around shoot becomes
humid.
Difference in concentration
of water vapour inside the
leaf and in the air around
leaf decreases.

69. Functions of transpiration
1. The plant cools as water evaporates.
2. Water is transported up the plant as water is
lost from the shoot – keeps cells turgid.
3. Dissolved salts move up too.

70. What is the picture showing?
The plant lost No loss in weight
weight as water as the water
evaporates in to which
the air. evaporated, retur
ned to flask.
2
1

71. QUESTION: MAY, 2012
Comment on the biological significance of the
following statement:
Transpiration may have some useful effects in
plants. (4)

72. Plant adaptations
to reduce water loss

73. 1. Reduced leaf area – e.g. in cacti and pine

74. 2. Hairs on leaves to trap moisture

75. 3. Thick waxy cuticle – reduces transpiration by:
i) acting as a barrier to evaporation
ii) the shiny surface reflects heat and so lowers
temperature
Holly

76. 4. Stomata on lower surface of leaves
– as more water would be lost if stomata
were on the upper epidermis as the sun
acts directly on this surface.

77. 5. Sunken stomata trap still, moist air above
the stomata, so reducing transpiration.

78. Notice the thick cuticle

79. Adaptations of plants which live in
dry habitats

80. 1. Succulent leaves or stems (most cacti)
to store water.

81. 2. Shallow, but extensive root systems

82. What is the advantage of having both
shallow and deep roots?

83. QUESTION: MAY, 2006
Olive trees (Olea europaea) are native to the
Mediterranean region and other hot, arid regions.
Give TWO adaptations which plants living in this
region show to reduce the rate of transpiration. (2)
1. Thick waxy cuticle.
2. Dense cover of short hairs on underside of
leaves.
3. Relatively small leaves.
4. Sunken stomata.

84. THE END