plants use sunlight and water with carbon dioxide to make food. they store sugar as starch grains in...
TRANSCRIPT
Plants use sunlight and water with Carbon Dioxide to make food. They store sugar as starch grains in the chloroplasts. Oxygen gas is produced in all plants, even those which live under water.
6CO2 + 6H2O C6 H12 O6 + 6O2
light
sunlight
upper epidermis
vacuole
chloroplasts
cytoplasm
leaf vein
air spaces
palisadecells
spongylayer
Light is absorbed by the green coloured chlorophyll,
and the leaf uses the energy in the light to combine carbon
dioxide and oxygen.
Plants normally get their light from the Sun, but in this experiment the
light source is an electric bulb.
The energy changes in a light bulb are :
ELECTRICAL LIGHT + HEAT
Might the heat of the light bulb have an effect?
Is there anything that could be done to get rid of the effect of the heat?
What About the Colour of the Light?
The light bulb gives out white light, which is made of different colours & each
colour has its own wavelength.
Chlorophyll is green in colour, so green light is reflected away from the leaf – how could you test
to see which colour is best for photosynthesis?
The pondweed gives off oxygen when the light is on. Once the two minutes are up, the syringe is pulled out and the amount
of oxygen is measured.
The light is moved to different positions so that the light intensity changes.
Volume of Oxygen Produced Against Light Intensity
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
0 10 20 30 40 50 60 70 80 90 100
Light Intensity
Vo
lum
e o
f O
xyg
en
3% carbon dioxide
0.7% carbon dioxide
Evaluation
1 Explain what was done to make the experiment as accurate as possible.
2 Why were the experiments repeated?
3 Can you think of any extra measurements that could have been carried out.
4 Did the prediction come true?
5 Can you think of how the experiment can be improved?
Using an oxygen probe to
measure the concentratio
n in the water.
Putting sodium Bicarbonate into
the water to saturate it with Carbon dioxide.
Carbon filament lamps give out
better wavelength
distributions.Darken room to ensure that light
intensity is constant.
Putting a glass block between the plant and
the light source to prevent the heat reaching
the plant.
Add different concentrations of Carbon Dioxide into the water to see how it affects
the rate of photosynthesis.
Using the oxygen probe to measure the % Dissolved
Oxygen concentration in the water.
Once you have identified the best distance then you can identify the best Carbon
Dioxide concentration.
ALL THE BEST