Transcript Plants

Plant Structure & Transport
Chapter 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
Typical
Plants
Have:
Leaves
stem
roots
Flowers
Shoot & Root Systems
Typical plant has:
a) Shoot system – all parts above the ground
e.g. stem, leaves, buds, flowers
b) Root system – all parts below ground
Functions of Parts of Plant
Part
Function
Root
1. Anchors plant in the ground.
2. Takes in water and minerals from the soil
3. Some roots store food e.g. carrot
Stem
1.
2.
3.
Holds up the leaves, flowers and fruits
Carries water and minerals from the roots to leaves
and flowers
Carries food made in the leaves to other parts of the
plant
Leaves
1. Makes food and oxygen in photosynthesis
2. 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
Leaf structure
Greener on top
CO2 gets in
here
Leaf diagram – palisade layer
Most
chlorophyll
CO2
Leaf cell
Position?
Upper surface of leaf
Features?
Box shape
Chloroplasts
Function?
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
Guard
cell
oxygen
Provided plant is
photosynthesising
Carbon
dioxide
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 Plants
Plants 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 & Phloem
Xylem – 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 xylem
3. In the leaves some of the water is used to make
food in photosynthesis
4. 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/B
Method:
1. Set up apparatus as shown in diagram
2. Mark the level of water in each test tube at
the start of the experiment.
3. Set the tubes aside for two to three days
4. 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
Root hair cells
(x150)
Root ‘B’ has had
the hairs damaged -
Toughened root cap
To show the path of water through plant tissue
Apparatus: 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 the
Leaves. 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 Transpiration
1. 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 paper
Result:
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.
Junior Cert Past Papers
2009 Paper > Question 1 > Part a