1. Lesson 4 – Factors affecting photosynthesis

2. Learning outcomes Success criteria
By the end of this lesson I will know –
The principles of limiting factors as applied to the effects of temperature, carbon dioxide concentration and light intensity on the rate of photosynthesis
I will achieve these outcomes by-
Using your knowledge of limiting factors to enhance growth in commercial glasshouses
Evaluating applications using data

3. Starter Write down your own definition of a limiting factor.
It limits the rate at which the process can take place. The rate of process at any given time is not affected by all factors, but rather by the one whose level is at the least favourable.
Give an example of a limiting factor
Light intensity, amount of carbon dioxide and temperature

4. How light intensity affects the rate of photosynthesis
Using knowledge from KS4 describe what would happen in the following conditions.
In complete darkness
Providing more light
Maximum light intensity
Try to refer to carbon dioxide or temperature in your answers to 1 and 3

5. Using pages 72-73 peer assess your answers, add to your answers if necessary
Complete darkness – Even if we were to change the amount of carbon dioxide and temperature there would be no photosynthesis.
Increasing the amount of light would gradually increase the rate of photosynthesis
There becomes a point where increase in light intensity has no effect on the rate of photosynthesis. At this point some other factor such as carbon dioxide is in short supply so limits the process . Carbon dioxide is now the limiting factor and so on.
At any given moment , the rate of physiological process is limited by the factor that is at its least favourable value = law of limiting factors

6. Tasks Read through page 72-73
Describe what kind of conditions are needed in a glasshouse for optimal growth and why?
You must include
– Biochemical explanations.
Why each factor is needed?
Using your knowledge of the light independent reaction explain why at 25oC, raising the level of carbon dioxide from 0.04% to 0.1% increases the amount of carbon dioxide produced.

7. Plenary
Describe to your neighbour what is happening at each stage of the graph

9. Learning outcomes Success criteria
By the end of this lesson I will know –
The principles of limiting factors as applied to the effects of temperature, carbon dioxide concentration and light intensity on the rate of photosynthesis
I will achieve these outcomes by-
Using your knowledge of limiting factors to enhance growth in commercial glasshouses
Evaluating applications using data