Class:
Name:

)
Date:
Transpiration, transport and
support in plants
10
10.1
(
Transpiration (Book 1B, p. 10-3)
Transpiration (蒸騰) is the loss of water vapour to the atmosphere from the surface of plants
due to (1) _______________.
 Go to …
Practical 10.1 Demonstration of the occurrence of transpiration
(Book 1B, p. 10-3; Practical Workbook for SBA 1B, p. 10-1)
Where does transpiration take place? (Book 1B, p. 10-4)
A

Transpiration takes place in different parts of a plant.
1
Most water lost through the (2) _______________ of
the leaves and young stems.
water loss
water loss
2
Some water lost through the (3) _______________ of
the leaves and young stems.
3
In woody plants, a very small proportion of water
lost through the (4) _______________ of the woody
water loss
stems.
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How does transpiration take place in leaves? (Book 1B, p. 10-5)
B
iii
ii
i
a
b
 Process of transpiration and creation of transpiration pull in the leaves
Process of transpiration
a
Water on the surface of mesophyll cells
Water loss from the mesophyll cells
decreases the water potential of the cells.
(5) _______________ ______________.
Water is drawn from the neighbouring
The air space becomes
cells by (8) _______________.
ii
The neighbouring cells continue to
Water vapour in the air space diffuses to
drawn water from their neighbouring
the atmosphere through the
cells in the same way.
(7) _______________ due to higher
iii
Water is finally drawn from the
water vapour concentration in the air
(9) _______________ vessels, creating
space.
the transpiration pull (蒸騰拉力).
What is the significance of transpiration? (Book 1B, p.10-6)
C

i
evaporates into the
(6) _______________ with water vapour.
2
Creation of transpiration pull
Transpiration produces a (10) _______________ _______________ to prevent the plants from
being overheated in hot conditions.

Transpiration creates transpiration pull which transports water and
(11) _______________ along the xylem vessels and helps absorption of water and
minerals from the soil into the roots.
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D

How do we measure the rate of transpiration? (Book 1B, p. 10-7)
The rate of transpiration can be measured with a (12) _______________ (蒸騰計).
 Go to …
Practical 10.2 Measurement of the rate of transpiration using a bubble potometer
(Book 1B, p. 10-7; Practical Workbook for SBA 1B, p. 10-3)
Practical 10.3 Measurement of the amount of water absorbed and lost by a plant using a weight
potometer
(Book 1B, p. 10-8; Practical Workbook for SBA 1B, p. 10-6)
E
What environmental factors affect the rate of transpiration?
(Book 1B, p. 10-8)
Factor
Light intensity
Effect on the rate of transpiration

rate of
transpiration
The rate of transpiration (13) decreases/increases with an
increase in light intensity.

In darkness, the stomata (14) close/open, so that the rate of
transpiration (15) decreases/increases.

As the light intensity increases, the stomata open wider.
(16) Less/More water vapour in the air space diffuses out
light intensity
Air movement
through the stomata.

rate of
transpiration
The rate of transpiration (17) decreases/increases in windy
conditions.

In still air, the water vapour that diffuses out of the leaves
accumulates around the stomata.

Wind blows away the water vapour and prevents the
(18) decrease/increase in the concentration gradient of water
wind speed
Relative humidity
vapour, hence (19) decreases/increases the rate of diffusion.

rate of
transpiration
The rate of transpiration (20) decreases/increases with an
increase in the relative humidity.

A higher relative humidity of the surrounding air
(21) decreases/increases the concentration gradient of water
vapour between the air space and the surrounding air.
(22) Less/More water vapour diffuses out through the stomata.
relative humidity
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 Go to …
Practical 10.4 Design an investigation of the effects of environmental factors on the rate of transpiration
(Book 1B, p. 10-9; Practical Workbook for SBA 1B, p. 10-9)
Quick check
10.2
(Book 1B, p. 10-10)
Transport in flowering plants (Book 1B, p. 10-11)
Where does transport take place in flowering plants? (Book 1B, p. 10-11)
A

In flowering plants, substances are transported through the vascular tissue (維管組織).

The vascular tissue consists of (1) _______________ and (2) _______________. It is
arranged in long, separate strands called (3) _______________ _______________.
The distribution of the vascular bundles in dicotyledonous plants:
In the leaves,

xylem
the vascular bundles are in the large central
(4) _______________ and a network of small veins.
phloem
In the stems,

phloem
the vascular bundles are separate and usually arranged
xylem
in a ring at the (5) _______________.

(6) _______________ is located in the inner
region; (7) _______________ is located in the
outer region.
In the roots,

the vascular bundles are located at the
phloem
(8) _______________.

phloem tissue is found between the xylem tissues.
xylem
 Go to …
Practical 10.5 Examination of the vascular tissues of a young dicotyledonous plant
(Book 1B, p. 10-12; Practical Workbook for SBA 1B, p. 10-15)
40
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B
How do vascular tissues adapt to transport substances?
(Book 1B, p. 10-13)
1
Xylem (Book 1B, p. 10-13)

Xylem serves to transport (9) _______________ and (10) _______________ in the plants.

It mainly consists of xylem vessels (木質導管).
thick and (11) _______________ (木質化的) cell wall

provides support to the plant
continuous (12) _______________ tube

allows water to move along the vessel with little
resistance
no (13) _______________ ______________ between cells

allows water to move freely from one cell to another
 Structure of xylem vessels
2
Phloem (Book 1B, p. 10-14)

Phloem serves to transport (14) _______________ _______________ in the plants.
(15) _______________ _______________ (篩板)

with pores for organic nutrients to pass through
(16) _______________ _______________ (篩管)

living cell containing cytoplasm but no nucleus

allows organic nutrients to move along with little
resistance
(17) _______________ _______________ (伴細胞)

narrow cell beside each sieve tube

supports metabolism of sieve tubes
 Structure of phloem
 Go to …
Practical 10.6 Investigation of the plant tissue responsible for water transport
(Book 1B, p. 10-13; Practical Workbook for SBA 1B, p. 10-18)
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How are water and minerals transported in flowering plants?
C
(Book 1B, p. 10-15)
3
leaf
Water is drawn up the
xylem vessel by
4
2
Water is drawn from
(21) _______________
neighbouring cells, and
_______________.
eventually from the
Water is drawn into the
(20) _______________
roots from the soil by
_______________ in the
(22) _______________.
leaf.
1
Water (18) ___________
from the mesophyll
cells and
(19) _____________ out
of the stomata.
root
xylem vessel
 Pathway of water movement in plants

Minerals dissolve in the soil water and transported up the plant along with water.
How are organic nutrients transported in flowering plants?
D
(Book 1B, p. 10-16)

(23) _______________ (輸導) refers to the transport of (24) _______________
_______________ produced in the leaves by photosynthesis along (25) _______________
to the growing regions like buds or storage organs like fruits and roots.
 Go to …
Quick check
10.3
(Book 1B, p. 10-17)
Support in plants (Book 1B, p. 10-18)
The need of support in terrestrial plants:

To receive the (1) _______________ amount of sunlight for photosynthesis by holding the
leaves in the best position

To increase the chance of (2) _______________ and for better dispersal of fruits and seeds
by raising their flowers to a higher position
42
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Support in plants is provided by:
1
(3) _______________ of thin-walled cells;
2
(4) _______________ of thick-walled cells.
A

Turgidity of thin-walled cells (Book 1B, p. 10-18)
Young stems and (5) _______________ parts of dicotyledonous plants are mainly
supported by the turgidity of thin-walled cells in the (6) _______________ and pith.
When water supply is adequate


B

The cells are (7) _______________ and
When water supply is inadequate

The cells are (8) _______________ and
press against each other to give support to
cannot press against each other and give
the plant.
no support to the plant.
The plant stands upright.

The plant (9) _______________ (凋謝).
Rigidity of thick-walled cells (Book 1B, p. 10-19)
Thick-wall cells in stems are mostly (10) _______________ _______________, which have
thick cell walls and contain (11) _______________. They are hard and rigid which is
independent of the water content of the plant.

(12) _______________ plants are mainly supported by the hard wood tissues formed by old
xylem tissues.
 Go to …
Quick check
(Book 1B, p. 10-20)
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Exercise
The diagram below shows a potometer which can be used to estimate the transpiration rate of a
leafy shoot.
leafy shoot
reservoir
graduated air
capillary
bubble
tube
water
A student used the potometer to investigate the effect of air movement on the rate of
transpiration. He placed the potometer near a fan for 15 minutes. He then switched on the fan
for another 15 minutes. The results are shown in the table below.
Initial reading
Final reading
First 15 minutes (fan switched off)
0 mm
24 mm
Following 15 minutes (fan switched on)
24 mm
54 mm
a
Calculate the rate of transpiration, in mm/minute,
i
in the first 15 minutes.
(1 mark)
________________________________________________________________________
ii
in the following 15 minutes.
(1 mark)
________________________________________________________________________
b
Compare the answers in ai and aii. Account for the difference.
(4 marks)
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
c
Explain why the actual values should be smaller than the values calculated in a.
(2 marks)
____________________________________________________________________________
____________________________________________________________________________
44
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d
Another student tries to investigate the effect of light on the rate of transpiration using the
potometer. He placed a lamp near the potometer and switched it on. Explain how the
transpiration rate would be affected by the increase in light intensity.
(3 marks)
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
Total: 11 marks
－ END －
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Answers
Ch 10 Transpiration, transport and support in plants
10.1
1
evaporation
2
stomata
3
cuticle
4
lenticels
5
air space
6
saturated
7
stoma
8
osmosis
9
xylem
10
cooling effect
11
minerals
12
potometer
13
decreases/increases 14
close/open
15
decreases/increases
16
Less/More
17
decreases/increases 18
decrease/increase
19
decreases/increases 20
decreases/increases
21
decreases/increases 22
Less/More
1
xylem
2
phloem
3
vascular bundles
4
midrib
5
periphery
6
xylem
7
phloem
8
centre
9
water
10
minerals
11
lignified
12
hollow
13
end wall
14
organic nutrients
15
sieve plate
16
sieve tube
17
companion cell
18
evaporates
19
diffuses
20
xylem vessel
21
transpiration pull
22
osmosis
23
Translocation
24
organic nutrients
25
phloem
1
maximum
2
pollination
3
turgidity
4
rigidity
5
non-woody
6
cortex
7
turgid
8
flaccid
9
wilts
10
xylem vessels
11
lignin
12
Woody
10.2
10.3
Exercise
a
b
i
(24–0) / 15 = 1.6 mm/min
1m
ii
(54–24) / 15 = 2 mm/min
1m
The transpiration rate in the following 15 minutes is higher than that in the first 15 minutes.
1m
The wind blows away the water vapour accumulated around the stomata.
1m
This prevents the decrease in the concentration gradient of water vapour. between the air space in the leaf and the surrounding
c
air.
1m
The rate of diffusion of water vapour out of the stomata increases, thus the rate of transpiration increases.
1m
The potometer measures the rate of water absorption instead of the rate of transpiration.
1m
The rate of water absorption is higher than the rate of transpiration because some of the water absorbed is used by the plant for
d
growth.
1m
The transpiration rate would increase.
1m
Under high light intensity, the stomata open wider.
1m
More water vapour diffuses out of the stomata.
1m
46
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