Transcript Photosynthesis Testing leaves for Starch

Photosynthesis
In these lessons we will:
» Revise photosynthesis
» Use a practical activity to look at the
conditions needed for photosynthesis to
happen
» Investigate photosynthesis using algae
Revising photosynthesis
What is photosynthesis?
Why do plants do it?
How would a person tell if a plant is
photosynthesisng?
Photosynthesis
Carbon
dioxide
light
energy
Water
Glucose
Chlorophyll
Oxygen
So photosynthesis makes oxygen and glucose.
How could a plant be tested for these?
An alternative is to test for a substance that
plants make from glucose.
What do plants make from glucose?
STARCH !
So the plant could be tested for starch
to show it had been photosynthesising.
Now the class will carry out some practical work
on Geranium plants.
Each group is trying to find out what is
necessary for photosynthesis
Starch will be present if
the plant has been
photosynthesising.
» Step
» Boil leaf in water for a
few minutes
» Boil leaf in alcohol for
a few minutes
» Place leaf in hot water
for 30 seconds
» Add Iodine to leaf
» Reason
» To soften cells in leaf
» To remove green pigment
(chlorophyll)
» To re-soften cells in leaf
» To stain any starch in leaf
Use a white board to collect and record the results
Leaf group 1
Leaf group 2
Leaf group 3
Leaf group 4
What have you learned?
• Which leaves had starch present?
• What is necessary for photosynthesis?
So for photosynthesis plants need?
Carbon
dioxide
light
energy
Water
Glucose
Chlorophyll
Oxygen
Write – up your practical.
• Describe what you did
• Describe your results
• Explain what the results mean.
Practicals
Using algal cells to investigate photosynthesis
The class will now carry out some practicals
to investigate photosynthesis using algal cells.
Initially the algal cells will need to be immobilised
using a simple immobilisation technique
that your teacher will show you.
Refer to guide as necessary
Investigations into photosynthesis
The immobilised algal cells can be used to investigate
the effects of a variety of factors on photosynthesis.
When completing an investigation it would be
good practice to complete it in the standard format.
The teacher will advise you on this.
You should by now have a good understanding of
the factors that affect the rate of photosynthesis.
Write down what they are and what affect they have
on a plants rate of photosynthesis.