plant structure & transport chapter 13 objectives: ob46: associate the transport of water and...
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Plant Structure & TransportChapter 13
Objectives:OB46: Associate the transport of water and minerals in the plant with the xylem and the transport of food in the plant with phloem
OB47: Carry out simple experiments to show the path of water through plant tissue, and show that water evaporates from the surface of a leaf by transpiration
Shoot & Root Systems
Typical plant has:a) Shoot system – all parts above the grounde.g. stem, leaves, buds, flowers
b) Root system – all parts below ground
Functions of Parts of PlantPart Function
Root 1. Anchors plant in the ground.2. Takes in water and minerals from the soil3. Some roots store food e.g. carrot
Stem 1. Holds up the leaves, flowers and fruits2. Carries water and minerals from the roots to leaves
and flowers3. Carries food made in the leaves to other parts of the
plant
Leaves 1. Makes food and oxygen in photosynthesis2. Allows for the exchange of oxygen and carbon dioxide gas.3. Allows the loss of water vapour.
Flowers 1. Sexual reproduction and to produce seeds.
Function of leaves
• Trap light energy for photosynthesis
• Exchange of gases – oxygen and carbon dioxide
Structure of leaf
Wide
Helps to catch more light energy
Thin
Helps get carbon dioxide from bottom to top of leaf for photosynthesis
Gas exchange • Leaves are designed to allow carbon dioxide to get to the main chlorophyll
layer at the top of the leaf• They have small holes called stomata on the under surface
• Each hole is open & closed by 2 guard cells
Stoma is a small hole usually on under surface of leaf
Its size is controlled by 2 guard cells
closed open
Stoma function is for gas exchange in the leaf
Carbon dioxide
oxygenGuard cell
Provided plant is photosynthesising
Stomata open and close at different times of the day
When it is light the plant needs CO2 for photosynthesis so the stoma open
At night (darkness) they close
Gas exchange
Carbon dioxide enters the leaf through the stomata for photosynthesis and oxygen leaves the leaf as a waste product of photosynthesis
Transport in PlantsPlants have a transport system to move food and
wastes around the plant.The transport tissue in a plant consists of fluid filled
tubes called xylem and phloem.
Xylem & PhloemXylem – Carries water and minerals from the roots upwards to the leaves and
flowers.
Phloem – Carries food e.g. glucose made in the leaves to all the other parts of the plant.
Passage of water and minerals through a plant
1. Water is taken into the roots of a plant from the soil
2. It travels up the stem to the leaves in the xylem3. In the leaves some of the water is used to make
food in photosynthesis4. The remaining water passes out of the leaves into
the air.
Draw fig 13.4 pg 81
Experiment to show that water is lost from a plant
Pg. 82 T/BMethod: 1.Set up apparatus as shown in diagram2.Mark the level of water in each test tube at
the start of the experiment.3.Set the tubes aside for two to three days4.Again mark the level of water in each test
tube.
Result
Result: The level of water in the test tube with the seedling (test tube A) has fallen. The level of water in the other test tube (test tube B) stays the same
Conclusion: The fall of the water level in test tube A with the seedling suggests that water has passed through the plant and out into the air.
Wheat seed
Root hairs
Fragile parts of cells that grow from the main root
They massively increase the surface area for absorption
To show the path of water through plant tissueApparatus: Beaker, knife, cutting board, celery,
Food dye.
Method:
1. Set up apparatus as shown
in diagram
1. Leave the celery for a few days.
2. Remove the piece of celery and describe the appearance of the leaves and stem.
4. Place the piece of celery on a cutting board and using a knife cut across the
stem.
5. Look at the cut stem.
Results: The veins in the leaves
of the celery will be a red colour. Tiny red dots will be found at the edge of the stem. These are the transport tubes that carry the water.
Conclusion:Water travels up through
the stem and into theLeaves. The red dots
represent the xylem tubes which carry water up the plant.
Transpiration
Transpiration is the loss of water vapour from the surface of a plant.
Water is lost through tiny openings in the leaves called stomata.
As water is lost from the stomata more water is pulled up through the plant and this process is called the transpiration stream.
Functions of Transpiration1. To bring water needed for photosynthesis from the
roots to the leaves
2. To carry minerals dissolved in water up the plant
3. To cool the plant
Experiment: To show that water evaporates from the surface of a leaf by transpiration
Required: two plants, blue cobalt chloride paper, plastic bags, rubber bands.
Note: Blue cobalt chloride paper turns pink if water is added.Method:1. Set up apparatus as shown in 2. diagram.3. Leave the plants in a warm bright place for several hours.4. The plastic bags covering the soil in each pot prevent
evaporation of water
5. After several hours remove the bag covering each plant.
6. Test the liquid formed with blue cobalt chloride paperResult: Droplets of a colourless liquid have collected inside the
plastic bag covering the leaves of the plant (a). There are no droplets of liquid in bag from plant (b).
The droplets of liquid turned the blue cobalt chloride paper pink
Conclusion: The liquid formed in bag (a) is water. No water formed
in bag (b) which was the control. Therefore water is lost from the leaves of the plant.
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