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
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.
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.
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.
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
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.
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
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).
42.
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.
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.
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.
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)
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.
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.
