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10 Transpiration, transport and
support in plants
10.1 Transpiration in plants
(Book 1B, p. 10-3)
(1) _______________ (蒸騰) is the loss of water in the form of water vapour from its surface
into the atmosphere.
Transpiration takes place mainly through the (2) _______________ of the leaves and young
stems. It also takes place through the (3) _______________ of the leaves and young stems, and
(4) _______________ on the woody stems.
Go to
Practical 10.1
Demonstration of the occurrence of transpiration
(Book 1B, p. 10-3; Practical Workbook for SBA 1B, p. 10-1)
A
How does transpiration take place through stomata?
(Book 1B, p. 10-4)
Water on the surfaces of the mesophyll cells (5) _______________ into the air space. The
air space becomes almost (6) _______________ (飽和) with water vapour.
The water vapour concentration in the air space is now (7) _______________ than that in the
atmosphere outside the leaf. Water vapour (8) _______________ through the stomata into
the atmosphere.
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B
Creation of transpiration pull
(Book 1B, p. 10-5)
During (9) _______________, mesophyll cells near the air space lose water continuously into
the air space. The water potentials of these mesophyll cells therefore (10) _______________.
Water is then drawn from the adjacent cells to these mesophyll cells by
(11) _______________.
The adjacent cells, in turn, draw water from their neighbouring cells.
Eventually, water is drawn from the (12) _______________ _______________.
(13) _______________ _______________ (蒸騰拉力) is created to pull water up the xylem
vessels from the roots.
C
1
Significance of transpiration
(Book 1B, p. 10-5)
Transpiration creates transpiration pull for the transport of (14) _______________ and
(15) _______________ in the xylem vessels.
2
Transpiration pull also helps the (16) _______________ of water by the roots.
3
During transpiration, the evaporation of water from the mesophyll cells removes
(17) _______________ from the leaves. This produces a cooling effect to prevent plants from
being (18) _______________ under hot conditions.
D
How are stomata distributed on leaves?
(Book 1B, p. 10-6)
Different types of plants have different numbers and distribution of stomata on their leaves.
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Type of plant
Distribution of stomata and other features on leaves
Terrestrial
Stomatal density on the upper epidermis is
dicotyledonous plants
(19) _______________ than that on the lower epidermis
(陸生雙子葉植物)
Submerged plants
Few or no stomata on both the upper and lower epidermis
Not covered with (20) _______________
Dissolved gases, water and minerals (21) _______________
directly into the leaves through all surfaces
Floating plants
Stomata on the (22) _______________ epidermis only
(23) _______________ epidermis not covered with cuticle
Gas exchange takes place mainly through the stomata on the
upper epidermis
Water and minerals diffuse directly into the leaves through the
lower epidermis
E
Structural adaptations of leaves to prevent excessive loss of
water through transpiration (Book 1B, p. 10-7)
Feature
Adaptation
Epidermis covered with
Cuticle is almost impermeable to water. This reduces
(24) _______________
water loss through leaf surfaces.
Few or no stomata on the
The upper epidermis is directly illuminated by the sun and
(25) _______________ epidermis
its temperature is (26) _______________. Few or no
of dicotyledonous leaves
stomata on it helps reduce water loss due to transpiration.
(27) _______________
(28) _______________ of the stomata reduces water loss
_______________ control the
through transpiration when plants are deficient in water.
opening and closing of stomata
Go to
Practical 10.2
Design an investigation of the relative abundance of stomata on both sides of a leaf
(Book 1B, p. 10-8; Practical Workbook for SBA 1B, p. 10-4)
Practical 10.3
Investigation of the stomatal density on the upper and lower epidermis of a leaf
(Book 1B, p. 10-9; Practical Workbook for SBA 1B, p. 10-9)
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F
Factors affecting the rate of transpiration
(Book 1B, p. 10-10)
A (29) _______________ (蒸騰計) can be used to measure the rate of transpiration of a plant.
Effects of different environmental factors on the rate of transpiration:
Factor
Effect on rate of transpiration
Reason
Light
The rate (30) _______________
As light intensity increases, the stomata
intensity
with an increase in light
open (31) _______________. The
intensity.
cross-sectional area for the diffusion of
rate of
transpiration
water vapour (32) _______________.
Water vapour diffuses out more rapidly.
In darkness, the stomata are closed. Only a
small amount of water vapour diffuses out.
light intensity
Temperature The rate (33) _______________
As temperature increases, the rate of
with an increase in
(34) _______________ of water from the
temperature.
surfaces of mesophyll cells increases.
rate of
transpiration
Water vapour diffuses out more rapidly.
temperature
Air
The rate (35) _______________
Wind blows away water vapour around the
movement
in windy conditions.
stomata. This helps maintain a steep
rate of
transpiration
(36) _______________ _______________
of water vapour between the air space and
the surrounding air. The rate of diffusion
increases.
wind speed
Relative
The rate (37) _______________
A higher relative humidity of the
humidity
with an increase in the relative
surrounding air (38) _______________ the
humidity of the surrounding air.
concentration gradient of water vapour
rate of
transpiration
between the air space and the surrounding
air. Less water vapour diffuses out.
relative humidity
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Go to
Practical 10.4
Measurement of the rate of transpiration using a bubble potometer
(Book 1B, p. 10-10; Practical Workbook for SBA 1B, p. 10-13)
Practical 10.5
Measurement of the amount of water absorbed and lost by a plant using a weight
potometer
(Book 1B, p. 10-11; Practical Workbook for SBA 1B, p. 10-16)
Practical 10.6
Design an investigation of the effects of environmental factors on the rate of
transpiration
(Book 1B, p. 10-13; Practical Workbook for SBA 1B, p. 10-19)
Practical 10.7
Design an investigation of the effect of leaf surface area on the rate of transpiration
(Book 1B, p. 10-14; Practical Workbook for SBA 1B, p. 10-25)
10.2 Absorption of water and minerals in plants
(Book 1B, p. 10-18)
In terrestrial plants, water and minerals are absorbed from the soil by the (1) ______________.
The absorption process is mainly driven by (2) _______________ _______________.
A
What is the structure of the root?
(Book 1B, p. 10-18)
(3) _______________
(4) _______________ (皮層)
xylem
vascular bundle
phloem
(5) _______________
_______________ (根冠)
▲ Structure of a dicotyledonous root
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Structure
Feature and function
Not covered with (6) _______________
Made up of thin-walled cells
Protects the inner tissues from (7) _______________ (感染)
Epidermis
With (8) _______________ _______________ (根毛) which provide a
large (9) _______________ _______________ for the absorption of
water and minerals
Made up of several layers of thin-walled cells
Cortex
Stores food in the form of (10) _______________
Allows the passage of water and minerals across the root
Xylem transports (11) _______________ and (12) _______________
Vascular bundle
Phloem transports (13) _______________
Protects the tip of the root
Root cap
Continually rubbed away and replaced by new cells
Adaptive features of roots for the absorption of water and minerals:
Feature
Adaptation
Provide a large (14) _______________ _______________
Highly branched
for the absorption of water and minerals
Epidermis not covered with
Allows water and minerals to pass through the epidermis
(15) _______________ and thus
into the root easily
permeable to water
Numerous (16) _______________ Provide a large surface area for the absorption of water
_______________
and minerals
(17) _______________ and fine
Help absorb water and minerals as they are in close contact
root hairs which can easily grow
with soil particles
between soil particles
Go to
Practical 10.8
Examination of the structure of roots
(Book 1B, p. 10-19; Practical Workbook for SBA 1B, p. 10-31)
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B
1
How are water and minerals absorbed by roots?
(Book 1B, p. 10-20)
Absorption of water
In leaves, water is lost continuously due to (18) _______________.
Water is drawn up the (19) _______________ _______________ by the
(20) _______________ _______________ from the roots to the leaves.
Water in the cortex cells near the xylem vessels of the roots enters the xylem vessels. This
decreases the (21) _______________ _______________ of the cytoplasm of the cortex
cells.
Water moves from the neighbouring cells to these cells by (22) _______________. A
water potential gradient set up across the cortex causes water to move inwards from cell
to cell by osmosis. Some water moves inwards along the (23) _______________
______________ without entering their cytoplasm.
As water is drawn into the inner cells, the water potentials of the root hair cells become
lower. The water potential of the soil is now (24) _______________ than those of the root
hair cells. Therefore, water in the soil enters the root hair cells by (25) _______________.
2
Absorption of minerals
The concentrations of minerals in the soil are usually lower than that in the root hair cells.
Minerals are mainly absorbed against the concentration gradient by
(26) _______________ ______________.
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10.3 Transport in plants
A
(Book 1B, p. 10-22)
What structures are responsible for transport in flowering
plants? (Book 1B, p. 10-22)
Xylem and phloem are (1) _______________ _______________ (維管組織) specialized for the
transport of substances in flowering plants.
1
Xylem
It is responsible for transporting water and minerals.
It mainly consists of (2) _______________ _______________ (木質導管).
Structure of xylem vessels:
thick and (3) _______________ (木質化的) cell wall:
provides (4) _______________ to the plant
continuous hollow tube with no (5) _______________ or nucleus:
allows water to flow with little resistance
no (6) _______________ _______________ between cells:
allows water to flow freely from one cell to another
2
Phloem
It is responsible for transporting organic nutrients.
Structure of phloem:
(7) _______________ _______________ (篩管)
contains cytoplasm but no (8) _______________
allows organic nutrients to move with little resistance
(9) _______________ _______________ (篩板)
with pores which allow organic nutrients to pass through
(10) _______________ _______________ (伴細胞)
contains cytoplasm and a nucleus
supports metabolism of the sieve tube
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B
How is vascular tissue distributed in flowering plants?
(Book 1B, p. 10-23)
Xylem and phloem are arranged in large, separate strands called (11) _______________
_______________ in flowering plants.
Distribution of the vascular bundles in the roots, stems and leaves of dicotyledonous plants:
In leaves:
Vascular bundles are found in the large
xylem phloem
central (12) _______________ and the
network of small veins.
small
vein
Xylem lies at the (13) _______________
midrib
vein
of phloem.
In stems:
xylem
Vascular bundles are separate and usually
phloem
arranged in a ring at the
(14) _______________.
(15) _______________ is located in the
inner region and (16) _______________
pith
in the outer region.
cortex
epidermis
In roots:
Vascular bundles are located at the
xylem phloem
(17) _______________.
Phloem is found between xylem.
cortex
epidermis
Go to
Practical 10.9
Examination of the vascular tissues of a young dicotyledonous plant
(Book 1B, p. 10-25; Practical Workbook for SBA 1B, p. 10-34)
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C
How are water and minerals transported in flowering plants?
(Book 1B, p. 10-25)
xylem vessels
Water is lost from leaves through (18) _______________. Transpiration pull is created.
The continuous hollow tube-like structure of xylem vessels allows a continuous stream of
water to be formed inside them. Water is drawn up the (19) _______________
_______________ by transpiration pull as a continuous stream. Minerals dissolved in water
are transported up the plant along with the water.
Water and minerals in the soil are absorbed into roots.
Go to
Practical 10.10
Investigation of the plant tissue responsible for water transport
(Book 1B, p. 10-26; Practical Workbook for SBA 1B, p. 10-40)
D
How are organic nutrients transported in flowering plants?
(Book 1B, p. 10-27)
Organic nutrients are transported from the site of production (e.g. leaves) to the parts where
they are consumed or (20) _______________.
The transport of organic nutrients in plants is called (21) _______________ (輸導).
Organic nutrients are transported in (22) _______________.
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10.4 Support in plants
(Book 1B, p. 10-29)
The importance of support in terrestrial plants:
1
To hold the leaves in the best position to receive the maximum amount of
(1) _______________ for photosynthesis
2
To raise their flowers to a higher position that favours (2) _______________ and
(3) _______________ of fruits and seeds
Support (支持) in plants is mainly provided by the (4) _______________ of thin-walled cells
and the (5) _______________ of thick-walled cells.
A
Turgidity of thin-walled cells
(Book 1B, p. 10-29)
Thin-walled cells provide support to herbaceous stems and other non-woody parts of plants.
Support provided by thin-walled cells is affected by the water supply:
When water supply is adequate
When water supply is inadequate
The thin-walled cells become
The thin-walled cells become
(6) _______________ and press against each
(7) _______________.
other.
The plant stands straight.
B
The plant (8) _______________ (凋謝).
Rigidity of thick-walled cells
(Book 1B, p. 10-30)
Thick-walled cells are mostly (9) _______________ _______________. Their cell walls
contain (10) _______________ (木質素), which makes them hard and rigid.
Support provided by thick-walled cells is independent of the water content of the plant.
As woody plants grow, more lignin is deposited in the cell walls of the older xylem. The older
xylem finally becomes (11) _______________, which provides great support to the plants.
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Answers
Ch 10 Transpiration, transport and support in plants
10.1
1
Transpiration
2
stomata
3
cuticle
4
lenticels
5
evaporates
6
saturated
7
higher
8
diffuses
9
transpiration
10
decrease
11
osmosis
12
xylem vessels
13
Transpiration pull 14
water
15
minerals
16
absorption
17
heat
18
overheated
19
lower
20
cuticle
21
diffuse
22
upper
23
Lower
24
cuticle
25
upper
26
higher
27
Guard cells
28
Closing
29
potometer
30
increases
31
wider
32
increases
33
increases
34
evaporation
35
increases
36
concentration gradient
37
decreases
38
decreases
10.2
1
roots
2
transpiration pull
3
epidermis
4
cortex
5
root cap
6
cuticle
7
infection
8
root hairs
9
surface area
10
starch
11
water / minerals
12
minerals / water
13
food
14
surface area
15
cuticle
16
root hairs
17
Long
18
transpiration
19
xylem vessels
20
transpiration pull
21
water potential
22
osmosis
23
cell walls
24
higher
25
osmosis
26
active transport
10.3
1
vascular tissues
2
xylem vessels
3
lignified
4
support
5
cytoplasm
6
end wall
7
sieve tube
8
nucleus
9
sieve plate
10
companion cell
11
vascular bundles
12
midrib
13
top
14
periphery
15
Xylem
16
phloem
17
centre
18
transpiration
19
xylem vessels
20
stored
21
translocation
22
phloem
10.4
1
sunlight
2
pollination
3
dispersal
4
turgidity
5
rigidity
6
turgid
7
flaccid
8
wilts
9
xylem vessels
10
lignin
11
wood
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