Limiting factors

The rate of photosynthesis depends on temperature and the availability of light and carbon dioxide.

If photosynthesis is to happen at its maximum rate, all environmental factors must be present at the optimum levels.

If one or more factors are in short supply, the rate of photosynthesis will be limited.

These factors are then limiting factors and the rate of photosynthesis will be determined by the factor that is in shortest supply.

Light

As light intensity increases so too does the rate of photosynthesis until a certain point where the graph levels off.

At lower light intensities, light is the limiting factor because an increase in light causes an increase in photosynthesis.

At higher light intensities (plateau of graph), further increasing the light intensity does not increase the rate of photosynthesis meaning that another factor is limiting photosynthesis.

On a hot day, photosynthesis happens at a higher rate when compared to the cooler day, showing that temperature has an effect and is the limiting factor on a cooler day.

Photosynthesis limiting temperature

An increased level of carbon dioxide leads to a higher rate of photosynthesis when compared to the lower carbon dioxide level.

Photosynthesis limiting factor CO2

This shows that the carbon dioxide level has an effect and is now limiting the rate of photosynthesis.

Carbon dioxide

As carbon dioxide concentrations increase, so too does the rate of photosynthesis until a certain point where the graph levels off.

At lower carbon dioxide concentrations carbon dioxide is the limiting factor because an increase in carbon dioxide causes an increase in photosynthesis.

At higher carbon dioxide concentrations (plateau of graph), further increasing the carbon dioxide concentration does not increase the rate of photosynthesis meaning another factor is limiting photosynthesis.

Temperature

Temperature affects all reactions because an increase in temperature causes the molecules involved to gain kinetic energy and therefore react more frequently.

However, a very high temperature can denature the enzymes involved in these reactions, reducing or even stopping the reaction completely.

Commercial growth

When growing crops it is important to reduce these limiting factors to increase the rate of crop growth and increase profits.