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1

Think about it
10.1
How is water lost in transpiration?
10.2
How are water and minerals absorbed in the roots?
10.3
How are water, minerals and organic nutrients transported inside plants?
10.4
How are plants supported?
Practical 10.1
Practical 10.4
Practical 10.7
Practical 10.2
Practical 10.5
Practical 10.8
Summary concept diagram
Practical 10.3
Practical 10.6
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2

Sally has bought a bunch of coloured flowers.
Have you seen artificially coloured flowers before?
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3

Sally has bought a bunch of coloured flowers.
How are flowers artificially made?
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4

Sally has bought a bunch of coloured flowers.
You can make coloured flowers by putting
white flowers, e.g. carnations ( 康乃馨 ), into a solution of food colouring.
The solution is absorbed and transported to the petals so that they turn to the colour of the food colouring after several days.
How are flowers artificially made?
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10.1
How is water lost in transpiration?
All organisms lose water all the time.

In plants: through transpiration ( 蒸騰作用 )
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6

10.1
How is water lost in transpiration?
The water lost must be quickly replaced .
 by absorption from soil in the roots
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10.1
How is water lost in transpiration?
Definition of transpiration:
The loss of water vapour from the surfaces of plants due to evaporation.
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8

10.1
How is water lost in transpiration?

> 90% of the total water loss from stomata
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9

10.1
How is water lost in transpiration?
 very small amount of water lost through cuticle
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10.1
How is water lost in transpiration?

< 10% of water loss through lenticels ( 皮孔 ) in woody stems
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10.1
Demonstration of the occurrence of transpiration
Procedure:
1 Set up the apparatus as shown in the diagram. intact potted plant bell jars plastic bags potted plant with the aerial parts removed
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10.1
Demonstration of the occurrence of transpiration
Procedure:
2 Leave both set-ups in bright light for 2 hours. intact potted plant bell jars plastic bags potted plant with the aerial parts removed
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10.1
Demonstration of the occurrence of transpiration
Procedure:
3 Observe any changes in the bell jars. Test any liquid formed on the walls with dry cobalt (II) chloride paper. intact potted plant bell jars plastic bags potted plant with the aerial parts removed
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10.1
How is water lost in transpiration?
Transpiration
The process of transpiration
A leaf section
1) Water on the surface of the mesophyll cells evaporates into the air space .
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10.1
How is water lost in transpiration?
Transpiration
The process of transpiration
A leaf section
2) Water vapour diffuses through the stomata to the outside down the concentration gradient .
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10.1
How is water lost in transpiration?
Transpiration
The creation of transpiration pull
A leaf section
1) Water is lost from the permeable cell wall , which is replaced by water in the cell.

Each cell then draws water from its neighbouring cells.
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10.1
How is water lost in transpiration?
Transpiration
The creation of transpiration pull
A leaf section
2) Cells draw water from the xylem vessels, pulling water up the plant.
 transpiration pull
( 蒸騰牽引力 ) is created
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10.1
How is water lost in transpiration?
Transpiration
Importance of transpiration
1) produces a cooling effect in the plant and helps leaves withstand high temperatures
2) helps in the absorption of water and minerals from the soil
3) causes the transport of water and minerals in plants
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Distribution of stomata on leaves in terrestrial and aquatic plants
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10.2
Design an investigation of the distribution of stomata on both sides of a leaf
Bobby observed that the dry cobalt (II) chloride paper on the underside of the leaf changed from blue to pink faster than the one on the upper surface. potted plant sellotape dry cobalt (ll) chloride paper on both sides of the leaf
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10.2
Design an investigation of the distribution of stomata on both sides of a leaf
He wondered if the result was due to different stomatal densities of both sides of the leaf. potted plant sellotape dry cobalt (ll) chloride paper on both sides of the leaf
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10.2
Design an investigation of the distribution of stomata on both sides of a leaf
Design and perform an experiment to compare the distribution of stomata on both sides of a leaf. potted plant sellotape dry cobalt (ll) chloride paper on both sides of the leaf
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Distribution of stomata on leaves in terrestrial and aquatic plants
Terrestrial dicotyledonous plants
• more stomata in the lower epidermis than the upper epidermis
• fewer stomata in the upper epidermis: reduce water loss
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Distribution of stomata on leaves in terrestrial and aquatic plants
Submerged leaves of aquatic plants
• no cuticle
• gases, water and minerals diffuse directly all over their surface
• few or no stomata in the upper and lower epidermis
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Distribution of stomata on leaves in terrestrial and aquatic plants
Floating leaves of aquatic plants
• have stomata in the upper epidermis only
• no stomata in the lower epidermis
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Distribution of stomata on leaves in terrestrial and aquatic plants
Plant species
Number of stomata per cm 2
Upper epidermis Lower epidermis
Terrestrial dicotyledons
Apple
Tomato
Submerged leaves of aquatic plants
0
1 200
0
14 100
13 000
0
Hydrilla
Floating leaves of aquatic plants
9 500 0
Water lily
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Extension
Measuring the rate of transpiration
• with a potometer ( 蒸騰計 ) a potometer
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Extension
10.3
Measurement of the rate of transpiration using a bubble potometer
Procedure:
1 Cut a leafy shoot from a plant and fit it tightly into the bubble potometer under water. Set up the apparatus as shown. Seal off all connections with vaseline to ensure no leakage of water. leafy shoot reservoir tap (closed) air bubble beaker water graduated capillary tube
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Extension
10.3
Measurement of the rate of transpiration using a bubble potometer
Procedure:
2 Lift the end of the capillary tube from the beaker of water for 30 s and then replace it to introduce an air bubble into the tube. leafy shoot reservoir tap (closed) air bubble beaker water graduated capillary tube
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Extension
10.3
Measurement of the rate of transpiration using a bubble potometer
Procedure:
3 Wait for the bubble to move into the horizontal graduated part of the capillary tube. leafy shoot reservoir tap (closed) air bubble beaker
4 Record the distance travelled by the bubble in a certain period of time
(e.g. 5 minutes). water graduated capillary tube
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Extension
10.4
Measurement of the amount of water absorbed and lost by a plant using a weight potometer oil layer
Procedure:
1 Cut a leafy shoot from a plant and fit it tightly into the weight potometer under water. burette water leafy shoot
2 Set up the apparatus as shown.
top pan balance
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Extension
10.4
Measurement of the amount of water absorbed and lost by a plant using a weight potometer oil layer
Procedure:
3 Record the initial water level
(V i
) in the burette and the weight (W i
) of the whole set-up. burette water leafy shoot
4 After 24 hours, record the final water level (V f
) and the weight
(W f
) of the whole set-up. top pan balance
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Extension
Effects of the environmental factors on the rate of transpiration
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Extension
10.5
Design an investigation of the effects of environmental factors on the rate of transpiration
Donna put some roses in her bedroom and some in the sitting room.
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Extension
10.5
Design an investigation of the effects of environmental factors on the rate of transpiration
Later, she found that the water level in the vase placed in the sitting room was much lower than that in the bedroom. She wondered if the environmental conditions have affected transpiration and water uptake of the flowers.
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Extension
10.5
Design an investigation of the effects of environmental factors on the rate of transpiration
Design and perform an experiment to find out the effects of an environmental factor on the rate of transpiration.
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Extension
Effects of the environmental factors on the rate of transpiration
• light intensity , the stomata open wider
 more water vapour in the air space can diffuse out
 rate of transpiration light intensity
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Extension
Effects of the environmental factors on the rate of transpiration
• temperature

(1) rate of evaporation and rate of diffusion of water vapour out of stomata

(2) relative humidity temperature
 rate of transpiration
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Extension
Effects of the environmental factors on the rate of transpiration
relative humidity
• relative humidity
 the concentration gradient of water vapour between the air space and the atmosphere
 less water vapour diffuse out through stomata
 rate of transpiration
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Extension
Effects of the environmental factors on the rate of transpiration
• air movement
 the concentration gradient of water vapour between the leaf and the drier air outside
 rate of diffusion wind velocity  rate of transpiration
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Brief Revision
1 The rate of transpiration can be measured
2 Terrestrial dicotyledonous plants usually have more / less stomata on the upper epidermis than the lower epidermis.
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Brief Revision
3 An increase in light intensity will increase / decrease the rate of transpiration.
4 An increase in relative humidity will increase / decrease the rate of transpiration.
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10.2 How are water and minerals absorbed in the roots?
Structure of the root root cap
• protects the tip of the root
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10.2 How are water and minerals absorbed in the roots?
Structure of the root epidermis
• made up of thin-walled cells
• protects the inner tissues from diseases
• not covered by cuticle
• has many root hairs
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10.2 How are water and minerals absorbed in the roots?
Structure of the root root hair
• provides a large surface area for water absorption
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10.2 How are water and minerals absorbed in the roots?
Structure of the root cortex
• consists of several layers of thin-walled cells
• stores starch
• allows the passage of water and minerals across the root
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10.2 How are water and minerals absorbed in the roots?
Structure of the root vascular bundle (維管束)
• transports materials into and out of the root
• made up of xylem ( 木質部 ) and phloem ( 韌皮部 ) tissues
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The adaptations of roots for absorption of water and minerals
1) Epidermal cells are not covered by cuticle and thus water can easily pass into them.
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The adaptations of roots for absorption of water and minerals
2) Numerous root branches and root hairs provide a large surface area for absorption of water and minerals.
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The adaptations of roots for absorption of water and minerals
3) The root hairs are long, fine structures .
 easily grow between the soil particles
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10.6
Examination of the structure of roots
Procedure:
1 Examine the external structures of the root with a hand lens. Draw a labelled diagram.
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10.6
Examination of the structure of roots
Procedure:
2 Examine the slide of the transverse section of the root with a microscope.
3 Identify the internal structures of the root. Draw a labelled diagram.
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Absorption of water in roots
1 Water moves into the root hairs by osmosis .
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Absorption of water in roots
2a Water moves into the neighbouring cortex cells by osmosis.
 it moves inwards from cell to cell
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Absorption of water in roots
2b Some water moves along the cell wall .
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Absorption of water in roots xylem vessel in the stem
3 Water is drawn up the xylem vessel by transpiration pull .
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Absorption of water in roots
4 Water evaporates from the leaf cells and diffuses out through the stomata as water vapour.
water vapour
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Absorption of minerals in the roots
Mineral salts dissolve in soil water to form ions ( 離子 ).
salts ions
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Absorption of minerals in the roots
Ions are absorbed into the roots by active transport , using energy from respiration.
salts ions
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Absorption of minerals in the roots
Some minerals are also absorbed in this way by diffusion .
salts ions
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Brief Revision
1 ____ ____ serves to protect the tip of the root.
2 _______ ______ consisting of xylem and phloem, serves to transport materials in and out of the root.
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Brief Revision
3 Root cells absorb water through osmosis
/ active transport / diffusion.
4 Minerals can be absorbed by plants through osmosis / active transport / diffusion.
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10.3 How are water, minerals and organic nutrients transported inside plants?
Transport in flowering plants is provided by the vascular tissues .
xylem phloem
Patterns ( 分佈 ) in the roots, stems and leaves are different.
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10.3 How are water, minerals and organic nutrients transported inside plants?
LEAF leaf vein mid-rib vein xylem phloem
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10.3 How are water, minerals and organic nutrients transported inside plants?
STEM phloem xylem pith ( 髓 ) epidermis cortex xylem phloem
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10.3 How are water, minerals and organic nutrients transported inside plants?
ROOT phloem xylem epidermis cortex phloem xylem
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10.7
Examination of the vascular tissues in a young dicotyledonous stem
Procedure:
1 Examine the slide of the transverse section of a young dicotyledonous stem with a microscope.
2 Identify the vascular tissues.
3 Draw a labelled diagram.
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10.3 How are water, minerals and organic nutrients transported inside plants?
Xylem
• mainly consists of xylem vessels
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10.3 How are water, minerals and organic nutrients transported inside plants?
3 characteristics:
Xylem
1) Thick cell wall
• contains cellulose ( 纖維素 ) and lignin ( 木質素 )
• provides support to the plant
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10.3 How are water, minerals and organic nutrients transported inside plants?
3 characteristics:
Xylem
2) Continuous hollow tube
• does not have cytoplasm or nuclei
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10.3 How are water, minerals and organic nutrients transported inside plants?
3 characteristics:
Xylem
3) No end wall between cells
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10.3 How are water, minerals and organic nutrients transported inside plants?
Phloem
3 components:
1) sieve plate ( 篩板 )
• the end wall between cells
• has holes for dissolved substances to pass through
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10.3 How are water, minerals and organic nutrients transported inside plants?
Phloem
3 components:
2) sieve tube ( 篩管 )
• living cylindrical cells contain cytoplasm but no nucleus
• cell wall is thin and does not contain lignin
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10.3 How are water, minerals and organic nutrients transported inside plants?
Phloem
3 components:
3) companion cell ( 伴細胞 )
• found alongside each sieve tube
• contains cytoplasm and a nucleus
• supports metabolism of sieve tubes
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Transport of water and minerals
Water and minerals are transported in xylem vessels .
 driven by transpiration pull
Transpiration pull is the suctional force generated by transpiration.
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10.8
Investigation of the plant tissue responsible for water transport
Procedure:
1 Immerse the roots of a herbaceous plant in dilute eosin solution for about
6 hours.
2 Cut transverse sections of the root, stem and leaf. Examine them with a microscope.
Identify the tissue(s) with red colour.
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Transport of organic nutrients
Organic nutrients are transported in phloem in 2 ways.
 up or down to the growing points for development
 down to the roots or other storage organs
The process is called translocation ( 輸導作用 )
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of water and minerals
1 Water and minerals are absorbed into the roots.
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of water and minerals
2 Water and minerals move up to other parts of the plant.
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of water and minerals
3a Water and minerals are used for metabolism.
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of water and minerals
3b Water is lost in transpiration.
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of organic nutrients
1 Organic nutrients are made in photosynthesis.
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of organic nutrients
2a Organic nutrients move down to growing fruit and roots for storage.
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Summary for the transport of water, minerals and organic nutrients in a plant
Transport of organic nutrients
2b Organic nutrients move up to the bud for growth and development.
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Brief Revision
1 Identify the following structures:
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Brief Revision
2 The process which organic nutrients are transported throughout the plants is
3 ______ is the main tissue which transports water in the plant, while transport of organic nutrients.
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Extension
10.4
How are plants supported?
Plants are supported in two ways:
1) Turgidity of thin-walled cells
2) Hardness of thick-walled cells
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Extension
10.4
How are plants supported?
In a condition of adequate
• water moves in by osmosis
 the cells become turgid water supply:
 press against each other plant stands upright
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Extension
10.4
How are plants supported?
In a condition of inadequate water supply:
• the cells will be plasmolysed
 become flaccid plant wilts ( 凋謝 )
 cannot press against each other
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Extension
10.4
How are plants supported?
Xylem vessels
 contain lignin , which makes them hard
 provide mechanical support to the plants
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Extension
10.4
How are plants supported?
As a woody plant ( 木質植物 ) grows, more and more xylem is formed.
new xylem cell  the older xylem tissues are pushed inwards and become wood mature xylem cell wood
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Summary concept diagram lose water in roots
Plants absorption takes place in absorb minerals by absorb water by diffusion active transport gain support by osmosis transpiration
E young woody stems
E turgidity of thin-walled cells in
E herbaceous plants
E hardness of thick-walled cells in
E woody plants
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Summary concept diagram transpiration creates transpiration pull affected by
E light intensity
E temperature
E relative humidity
E air movement
Back to summary concept diagram
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Summary concept diagram
Plants transport takes place in vascular tissues consist of xylem mainly consists of xylem vessels transport phloem transports organic nutrients water minerals
Back to summary concept diagram Back
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