Factors affecting photosynthesis - Light intensity

There are several ways of measuring the rate of photosynthesis in the lab. These include:

  • the rate of oxygen production (number of bubbles or volume of oxygen gas given off in a set time)
  • the rate of carbon dioxide uptake
  • the rate of glucose production

Several factors can affect the rate of photosynthesis:

  • light intensity
  • carbon dioxide concentration
  • temperature

Light intensity

Without enough light, a plant cannot photosynthesise very quickly - even if there is plenty of water and carbon dioxide.

Increasing the light intensity increases the rate of photosynthesis, until some other factor - a limiting factor - becomes in short supply.

Graph showing how increasing the light intensity increases the rate of photosynthesis

The rate of photosynthesis is directly proportional to the light intensity until another factor becomes limiting.

At very high light intensities, photosynthesis is slowed, but these light intensities do not occur in nature.