Limiting factors

Question 1

Name 3 limiting factors of photosynthesis

Answer 1

light intensity, carbon dioxide concentration and temperature

Question 2

How can you measure the effect of light intensity on photosynthesis?

Answer 2

• use an apparatus involving pondweed to measure the rate at which oxygen is given off
• vary the light intensity using bright and dim lights

Question 3

A graph measuring the rate of photosynthesis against the carbon dioxide concentration rises steadily and then remains the same

Explain each part of the graph

Answer 3

In the first part of the graph CO2 is a limiting factor, as it increases the rate of photosynthesis
More CO2 can be used to make sugars

Once CO2 concentration is high, another factor is limiting the rate of photosynthesis

Question 4

A graph measures the temperature against the rate of photosynthesis. It goes up and then down again.
Explain why.

Answer 4

Temperature is a limiting factor as it increases the kinetic energy of molecules and increases enzyme activity, speeding up the rate of photosynthesis
This causes the graph to rise

Once the temperature gets too high, enzymes start to denature and the rate of photosynthesis slows down