Limiting factors Questions

Question 1

A graph shows the rate of photosynthesis of a plant at different light intensities. At point A the graph is rising. At point B it is steady.

Explain the shape of the graph at points A and B.

Answer 1

At A, light intensity is limiting photosynthesis, because increasing the light intensity increases the rate of photosynthesis.

At B, light intensity is no longer the limiting factor because increasing the light intensity does not change the rate of photosynthesis.
Another factor, such as CO2 concentration or temperature, is limiting the rate of photosynthesis.

Question 2

Define the term limiting factor.

Answer 2

Something that limits the rate of photosynthesis when it is at a low level.

Question 3

Explain why measuring the oxygen given off by a plant is a way of measuring the rate of photosynthesis.

Answer 3

Photosynthesis produces oxygen. The more rapidly oxygen is released, the faster the photosynthesis reactions must be happening.