The Law of Limiting Factors

What can you remember about the Calvin Cycle?

• Glycerate-3-phosphate combines with CO2 to produce Triose Phosphate

• FALSE

• RuBP combines with CO2 to make Glycerate-3-phosphate

• Ribulose Bisphosphate has 5 carbon atoms

• TRUE

• The Calvin Cycle occurs in the grana

• FALSE

• It occurs in the stroma of the chloroplast

• Reduced NADP provides the electrons to reduce GP to Triose Phosphate

• TRUE

• Very little Triose Phosphate is used to regenerate RuBP

• FALSE

• 5 out of every 6 molecules is used

• Triose Phosphate has 6 carbon atoms

• FALSE

• It has three!

• The Calvin Cycle only occurs in the dark

• FALSE

• It happens all the time – it just doesn’t directly use light for the reactions

• Triose Phosphate is used to make glucose

• TRUE

Aim

• To remember the law of limiting factors.• To know factors which limit the rate of

photosynthesis• To be able to interpret limiting factor

graphs• To know how farmers control limiting

factors in commercial greenhouses.

• What environmental factors affect the rate of photosynthesis?

The law of limiting factors

• Photosynthesis will only proceed at the rate determined by the factor in shortest supply

How can we investigate the rate of photosynthesis?

• Volume of oxygen produced• Volume of carbon dioxide used up

Factors affecting the rate of photosynthesis

0

10

20

30

40

50

0 10 20 30 40 50

Light intensity/%

Nu

mb

er o

f b

ub

ble

s m

in-1

250C

100C

• Complete summary questions 1 and 2 page 43

How does this relate to growing crops?

• What sort of problems might this entail?

• Now follow the instructions at the top of page 17 in your booklet.

• Make a few notes on the different ways farmers control the productivity in greenhouses – ensure you link each to the rate of photosynthesis.

• Answer the questions from the text book pages 49 and 50.

Summary questions

• Page 43 text book• Q1 page 9 booklet

Question 3

• Increase the carbon dioxide or increase the temperature?

Answers

3. Increasing the CO2 concentration will have more effect because this increases the rate of photosynthesis more than raising the temperature

Question 4

• Why is it not worth heating the greenhouse on a dull day?

4. Because the light intensity will be limiting the rate of photosynthesis so increasing the temperature will have no effect.

Question 5

• Why does increasing the level of carbon dioxide increase the amount of glucose?

5. More CO2 is available to combine with RuBP to form more GP which will in turn be converted to triose phosphate and glucose