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Think about… 10.1 Transpiration 10.2 Transport in flowering plants 10.3 Support in plants Recall ‘Think about…’ Summary concept map
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A hollow tree
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A hollow tree The centre of the trunk has rotted away. But the tree is still growing actively!
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1 How can the tree transport water and food between its roots and leaves with the centre of its trunk rotted away
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2 What would happen to the tree if the decay occurred in the centre of its roots instead of the trunk Why
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3 How can the tree remain upright though its trunk is hollow
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10.1 Transpiration water lost from plant surface due to evaporation water absorbed through roots
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transpiration (蒸騰) 10.1 Transpiration
water lost from plant surface due to evaporation transpiration (蒸騰) water absorbed through roots
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Demonstration of the occurrence of transpiration A B
10.1 Transpiration 10.1 Demonstration of the occurrence of transpiration A B 1 Use plastic bags to enclose the lower parts of the plants and the pots. plastic bags
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10.1 Transpiration 10.1 2 Put the intact potted plant (A) inside a bell jar. This is the experimental set-up. A B plastic bags
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10.1 Transpiration 10.1 3 Put the potted plant (B) with the aerial parts, i.e. parts above the ground, removed inside another bell jar. This is the control set-up. A B plastic bags
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4 Leave both set-ups in bright light for 2 hours. A B
10.1 Transpiration 10.1 4 Leave both set-ups in bright light for hours. A B plastic bags
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10.1 Transpiration 10.1 5 Observe any changes in the bell jars. Test any liquid formed on the walls with dry cobalt(II) chloride paper. A B plastic bags
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Results and discussion
10.1 Transpiration 10.1 Results and discussion A layer of moisture and drops of liquid are formed on the wall of bell jar A. The liquid turns dry cobalt(II) chloride paper from blue to pink, indicating the presence of water.
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Results and discussion
10.1 Transpiration 10.1 Results and discussion Set-up B is the control. The bell jar remains clear. No liquid is formed inside the bell jar. The results show that water vapour is released from plant A but not from plant B. This indicates that transpiration takes place in the aerial parts of the plant.
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Results and discussion
10.1 Transpiration 10.1 Results and discussion The purpose of the pots enclosed in plastic bags is to prevent the respiration of soil organisms and the evaporation of soil water from affecting the results.
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Where does transpiration take place?
10.1 Transpiration Where does transpiration take place?
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10.1 Transpiration leaf stem
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10.1 Transpiration stem leaf
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10% of water lost through cuticle
10.1 Transpiration leaf 10% of water lost through cuticle 90% of water lost through stomata
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very small proportion of water lost through lenticels of woody plants
10.1 Transpiration stem very small proportion of water lost through lenticels of woody plants
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How does transpiration take place in leaves?
10.1 Transpiration How does transpiration take place in leaves? Animation 1 Water on the surface of mesophyll cells evaporates into the air space.
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How does transpiration take place in leaves?
10.1 Transpiration How does transpiration take place in leaves? 2 Water vapour in the air space diffuses to the atmosphere through the stoma.
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Creation of transpiration pull
10.1 Transpiration Creation of transpiration pull 1 Water lost from the surface of mesophyll cells is replaced by water in these cells.
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Creation of transpiration pull
10.1 Transpiration Creation of transpiration pull 2 Water is drawn from the neighbouring cells by osmosis.
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Creation of transpiration pull
10.1 Transpiration Creation of transpiration pull 3 Water is finally drawn from the xylem vessels, creating the transpiration pull (蒸騰拉力).
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Significance of transpiration
10.1 Transpiration Significance of transpiration 1 During transpiration, evaporation of water absorbs heat from the leaves. cooling effect
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transport of water and minerals along xylem vessels
10.1 Transpiration Significance of transpiration 2 Transpiration pulls water up through the plants. transport of water and minerals along xylem vessels
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absorption of water and minerals
10.1 Transpiration Significance of transpiration 3 Water and minerals are drawn into the roots from soil during transpiration. absorption of water and minerals
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By using a potometer (蒸騰計).
10.1 Transpiration How do we measure the rate of transpiration? By using a potometer (蒸騰計).
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Measurement of the rate of transpiration using a bubble potometer
10.1 Transpiration 10.2 Video Measurement of the rate of transpiration using a bubble potometer A bubble potometer can be used to measure the rate of water uptake by a leafy shoot. Since most of the water taken up by plants will eventually be lost through transpiration, it is assumed that the rate of water uptake is the same as the rate of transpiration.
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10.1 Transpiration 10.2 1 Cut a leafy shoot from a plant and fit it tightly into the bubble potometer under water.
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graduated capillary tube tap (closed)
10.1 Transpiration 10.2 2 Set up the apparatus. leafy shoot reservoir graduated capillary tube tap (closed) bubble water
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3 Seal off all connections with vaseline to ensure no water leakage.
10.1 Transpiration 10.2 3 Seal off all connections with vaseline to ensure no water leakage. 4 Lift the end of the capillary tube from the beaker of water for 30 seconds and then replace it to introduce an air bubble into the tube.
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10.1 Transpiration 10.2 5 Wait for the bubble to move into the horizontal graduated part of the capillary tube. 6 Record the distance travelled by the bubble in a certain period of time (e.g. 5 minutes).
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Results and discussion
10.1 Transpiration 10.2 Results and discussion The rate of water uptake can be found out by calculating the rate of movement of the air bubble, i.e. distance travelled by the air bubble per unit time. This is an indirect measurement of the rate of transpiration.
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Results and discussion
10.1 Transpiration 10.2 Results and discussion The leafy shoot should be cut and fit into the potometer under water. This prevents air bubbles from entering the xylem vessels of the plant and blocking water uptake.
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A weight potometer is comprised of two parts:
10.1 Transpiration 10.3 Video Measurement of the amount of water absorbed and lost by a plant using a weight potometer A weight potometer is comprised of two parts: (1) the burette which is used to measure the rate of water uptake by a leafy shoot (2) the balance which is used to measure the rate of water loss by the leafy shoot.
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2 Set up the apparatus as shown.
10.1 Transpiration 10.3 1 Cut a leafy shoot from a plant and fit it tightly into the weight potometer under water. 2 Set up the apparatus as shown.
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10.3 oil layer burette leafy shoot water top pan balance 10.1
Transpiration 10.3 oil layer burette leafy shoot water top pan balance
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10.1 Transpiration 10.3 3 Record the initial water level (Vi) in the burette and the weight (Wi) of the entire set-up. 4 After 24 hours, record the final water level (Vf) in the burette and the weight (Wf) of the entire set-up.
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Results and discussion
10.1 Transpiration 10.3 Results and discussion The amount of water absorbed by the plant = the change in volume of water in the burette = (Vf –Vi) The amount of water lost by the plant = the change in weight of the entire set-up = (Wf –Wi)
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Results and discussion
10.1 Transpiration 10.3 Results and discussion The amount of water absorbed is slightly greater than the amount of water lost by the plant. This is because some water is used in photosynthesis, growth and other metabolic activities.
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Factors affecting the rate of transpiration
10.1 Transpiration Factors affecting the rate of transpiration 1 Light intensity 2 Air movement 3 Relative humidity
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more water vapour diffuses out
10.1 Transpiration 1 Light intensity rate of transpiration light intensity stomata open wider more water vapour diffuses out transpiration rate light intensity
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2 Air movement rate of transpiration
10.1 Transpiration 2 Air movement rate of transpiration wind blows away water vapour around the stomata steep concentration gradient of water vapour maintained wind speed
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2 Air movement rate of transpiration diffusion rate
10.1 Transpiration 2 Air movement rate of transpiration diffusion rate transpiration rate wind speed
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3 Relative humidity rate of transpiration
10.1 Transpiration 3 Relative humidity rate of transpiration relative humidity of surrounding air concentration gradient of water vapour relative humidity
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less water vapour diffuses out
10.1 Transpiration 3 Relative humidity rate of transpiration less water vapour diffuses out transpiration rate relative humidity
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Donna put some roses in her bathroom and some in the sitting room.
10.1 Transpiration 10.4 Simulation Design an investigation of the effects of environmental factors on the rate of transpiration Donna put some roses in her bathroom and some in the sitting room.
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10.1 Transpiration 10.4 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 that environmental conditions had affected transpiration and water uptake by the plants.
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10.1 Transpiration 10.4 Design and perform an investigation to find out the effect of an environmental factor on the rate of transpiration.
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10.1 Transpiration 1 Transpiration is the loss of water vapour from the surface of plants due to evaporation It occurs through of leaves, of woody stems and stomata lenticels cuticle
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2a During transpiration, water flows from:
10.1 Transpiration 2a During transpiration, water flows from: xylem in leaves mesophyll cells air space atmosphere
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10.1 Transpiration 2b When water is continuously removed from the xylem vessels in leaves, a force called transpiration pull is created to pull water up the xylem vessels from the roots. transpiration pull
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3 Importance of transpiration to plants:
10.1 Transpiration 3 Importance of transpiration to plants: produces a effect on plants cooling results in transport of and along xylem vessels water minerals
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3 Importance of transpiration to plants:
10.1 Transpiration 3 Importance of transpiration to plants: aids in of water and minerals from the soil into the roots absorption
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rate of transpiration increases
10.1 Transpiration 4 Factors affecting rate of transpiration: increases light intensity increases air movement rate of transpiration increases
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rate of transpiration decreases
10.1 Transpiration 4 Factors affecting rate of transpiration: increases relative humidity rate of transpiration decreases
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10.2 Transport in flowering plants
Do flowering plants have a transport system like ours?
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their distribution in roots, stems and leaves are different
10.2 Transport in flowering plants transport in flowering plants is provided by vascular bundles (維管組織) xylem phloem 3D animation their distribution in roots, stems and leaves are different
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles LEAF midrib vein leaf vein in large central midrib and network of small veins
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles LEAF xylem phloem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles LEAF xylem phloem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles STEM arranged in a ring at the periphery xylem phloem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles STEM xylem phloem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles STEM xylem phloem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles at the centre ROOT phloem xylem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles ROOT xylem phloem
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Distribution of vascular bundles
10.2 Transport in flowering plants Distribution of vascular bundles ROOT xylem phloem
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Examination of the vascular tissues of a young dicotyledonous plant
10.2 Transport in flowering plants 10.5 Video Examination of the vascular tissues of a young dicotyledonous plant 1 Prepare temporary mounts of the transverse sections of the leaf, stem and root of a young dicotyledonous plant. Examine them or prepared slides under low power magnification.
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10.2 Transport in flowering plants 10.5 2 Identify the vascular tissues in each of the slides. Draw labelled diagrams of them.
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How are xylem and phloem adapted to transport substances?
10.2 Transport in flowering plants How are xylem and phloem adapted to transport substances?
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1 Xylem transports water and minerals consists of xylem vessels (木質導管)
10.2 Transport in flowering plants 1 Xylem transports water and minerals consists of xylem vessels (木質導管)
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1 Xylem thick and lignified cell wall provides support 10.2
Transport in flowering plants 1 Xylem thick and lignified cell wall provides support
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1 Xylem continuous hollow tube no cytoplasm or nuclei 10.2
Transport in flowering plants 1 Xylem continuous hollow tube no cytoplasm or nuclei
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1 Xylem continuous hollow tube
10.2 Transport in flowering plants 1 Xylem continuous hollow tube allows water to move with little resistance
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1 Xylem no end wall between cells
10.2 Transport in flowering plants 1 Xylem no end wall between cells allows water to move from one cell to another
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Investigation of the plant tissue responsible for water transport
10.2 Transport in flowering plants 10.6 Video Investigation of the plant tissue responsible for water transport Eosin is a red dye. When a plant absorbs the eosin solution, the tissue responsible for transporting water would be stained red.
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10.2 Transport in flowering plants 10.6 1 Immerse the roots of a herbaceous plant in dilute eosin solution for about 30 minutes. eosin solution
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10.2 Transport in flowering plants 10.6 2 Cut transverse sections of the root, stem and leaf of the plant. Examine them under a microscope. Identify the tissue(s) stained red. eosin solution
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Results and discussion
10.2 Transport in flowering plants 10.6 Results and discussion In the root, stem and leaf sections, only the xylem vessels are stained red. This shows that water is transported along the xylem vessels in the plant.
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2 Phloem transports organic nutrients
10.2 Transport in flowering plants 2 Phloem transports organic nutrients consists of sieve tubes (篩管) and companion cells (伴細胞)
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2 Phloem living sieve tube has cytoplasm but no nucleus 10.2
Transport in flowering plants 2 Phloem living sieve tube has cytoplasm but no nucleus
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2 Phloem living sieve tube
10.2 Transport in flowering plants 2 Phloem living sieve tube allows nutrients to move with little resistance
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2 Phloem sieve plate (篩板) has pores for nutrients to pass through 10.2
Transport in flowering plants 2 Phloem sieve plate (篩板) has pores for nutrients to pass through
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2 Phloem companion cell has cytoplasm and a nucleus 10.2
Transport in flowering plants 2 Phloem companion cell has cytoplasm and a nucleus
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2 Phloem companion cell supports metabolism of sieve tubes 10.2
Transport in flowering plants 2 Phloem companion cell supports metabolism of sieve tubes
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How are water and minerals transported?
10.2 Transport in flowering plants How are water and minerals transported? Water and minerals are absorbed in roots
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The main driving force is the transpiration pull
10.2 Transport in flowering plants How are water and minerals transported? The main driving force is the transpiration pull Water and minerals are absorbed in roots
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upper epidermis of the leaf
10.2 Transport in flowering plants How are water and minerals transported? upper epidermis of the leaf xylem vessel in leaf xylem vessel in stem stoma root hair
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How are water and minerals transported?
10.2 Transport in flowering plants How are water and minerals transported? 1 Water evaporates from the mesophyll cells and diffuses out through stomata.
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How are water and minerals transported?
10.2 Transport in flowering plants How are water and minerals transported? 2 Water is drawn from neighbouring cells, then from the xylem vessel.
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How are water and minerals transported?
10.2 Transport in flowering plants How are water and minerals transported? 3 Water is drawn up the xylem vessel by transpiration pull.
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How are water and minerals transported?
10.2 Transport in flowering plants How are water and minerals transported? 4 Water is drawn into the roots from the soil by osmosis.
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How are organic nutrients transported?
10.2 Transport in flowering plants How are organic nutrients transported? bud leaf stem fruit roots
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How are organic nutrients transported?
10.2 Transport in flowering plants How are organic nutrients transported? 1 Organic nutrients are made in leaves by photosynthesis.
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How are organic nutrients transported?
10.2 Transport in flowering plants How are organic nutrients transported? 2a Nutrients move down to growing fruits and roots for storage.
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How are organic nutrients transported?
10.2 Transport in flowering plants How are organic nutrients transported? 2b Nutrients move up to buds for growth and development.
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How are organic nutrients transported?
10.2 Transport in flowering plants How are organic nutrients transported? 2b Nutrients move up to buds for growth and development. translocation (輸導)
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10.2 Transport in flowering plants 1 In flowering plants, materials are transported in vascular bundles that consist of and phloem . xylem phloem
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10.2 Transport in flowering plants 2 Xylem mainly consists of vessels which are continuous hollow tubes made up of dead cells joined end to end. xylem vessels hollow
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3a Phloem consists of and .
10.2 Transport in flowering plants 3a Phloem consists of and sieve tubes companion cells
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10.2 Transport in flowering plants 3b Each sieve tube is a column of sieve cells joined end to end. The end walls between cells have many pores , forming the sieve plates . pores sieve plates
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10.2 Transport in flowering plants 4 In flowering plants, water and minerals are transported in xylem vessels from the roots up to the other parts of the plant. It is mainly driven by xylem vessels transpiration pull
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10.2 Transport in flowering plants 5 In flowering plants, organic nutrients are transported along from the leaves to the growing regions or storage organs. This process is called phloem translocation
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10.3 Support in plants Terrestrial plants need to stand upright and stretch out their branches to: receive maximum amount of sunlight favour pollination and dispersal of fruits and seeds
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turgidity of thin-walled cells rigidity of thick-walled cells
10.3 Support in plants support (支持) in plants turgidity of thin-walled cells rigidity of thick-walled cells
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turgidity of thin-walled cells
10.3 Support in plants turgidity of thin-walled cells cortex pith
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Turgidity of thin-walled cells
10.3 Support in plants Turgidity of thin-walled cells When water supply is adequate … xylem has a higher water potential than the cells in cortex and pith xylem
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Turgidity of thin-walled cells
10.3 Support in plants Turgidity of thin-walled cells When water supply is adequate … water moves from the xylem into these cells by osmosis
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Turgidity of thin-walled cells
10.3 Support in plants Turgidity of thin-walled cells When water supply is adequate … cells become turgid and press against each other
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Turgidity of thin-walled cells
10.3 Support in plants Turgidity of thin-walled cells When water supply is adequate … turgidity makes the whole stem strong enough to stand upright
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Turgidity of thin-walled cells
10.3 Support in plants Turgidity of thin-walled cells When water supply is inadequate … cells in the cortex and pith will become flaccid
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Turgidity of thin-walled cells
10.3 Support in plants Turgidity of thin-walled cells When water supply is inadequate … cells can no longer support the stem and the plant wilts (凋謝)
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turgidity of thin-walled cells rigidity of thick-walled cells
10.3 Support in plants support (支持) in plants turgidity of thin-walled cells rigidity of thick-walled cells
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thick, lignified cell wall
10.3 Support in plants hard and rigid thick, lignified cell wall rigidity of thick-walled cells xylem vessels
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cross-section of a young woody stem
10.3 Support in plants Rigidity of thick-walled cells xylem cells new xylem cell cross-section of a young woody stem As a woody plant grows, more and more xylem is formed
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cross-section of a young woody stem
10.3 Support in plants Rigidity of thick-walled cells next new xylem cell mature xylem cell cross-section of a young woody stem The older xylem tissues in stems are pushed inwards
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cross-section of a young woody stem
10.3 Support in plants Rigidity of thick-walled cells new xylem cell mature xylem cell wood cross-section of a young woody stem They finally become hard wood tissues provide support
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10.3 Support in plants 1 Dicotyledonous plants are supported by the of thin-walled cells in the cortex and pith of stem. turgidity
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10.3 Support in plants 2 Woody plants are supported mainly by the of thick-walled cells containing rigidity lignin
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1 How can the tree transport water and
food between its roots and leaves with the centre of its trunk rotted away? The vascular tissues remain unaffected because they are located at the periphery.
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2 What would happen to the tree if the
decay occurred in the centre of its roots instead of the trunk? Why? No substances can be transported and the tree will die soon because the vascular tissues are located at the central part.
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3 How can the tree remain upright though its trunk is hollow?
The thick-walled cells at the periphery of the stem are strong enough to provide support.
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Plants transpiration transpiration pull light intensity air movement
lose water in transpiration transpiration pull creates affected by light intensity air movement relative humidity
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Plants vascular tissue xylem phloem
transport takes place in vascular tissue consists of xylem phloem
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xylem xylem vessels water minerals
mainly consists of xylem vessels transport water minerals
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phloem sieve tubes companion cells organic nutrients
consists of sieve tubes companion cells transport organic nutrients
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turgidity of thin-walled cells rigidity of thick-walled cells
Plants gain support by turgidity of thin-walled cells rigidity of thick-walled cells
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