The Effect of 3 Factors on Photosynthesis (OCR Gateway GCSE Biology: Combined Science)

• In order to photosynthesise a plant needs light, water and carbon dioxide
• The availability of light and carbon dioxide can affect how much and how quickly (the rate) photosynthesis occurs
  • Water is not considered a limiting factor as there is usually enough water for photosynthesis
• The other major environmental factor that affects the rate of photosynthesis is temperature
• Chlorophyll can also be a limiting factor - disease or environmental stress (like lack of nutrients) can affect the amount of chlorophyll present in a plant

Temperature

• The temperature of the environment affects how much kinetic energy all particles have – so temperature affects the speed at which carbon dioxide and water move through a plant
• The lower the temperature, the less kinetic energy particles have, resulting in fewer successful collisions occurring over a period of time
• Increasing temperature increases the kinetic energy of particles, increasing the likelihood of collisions between reactants and enzymes which results in the formation of products
• At very high temperatures, however, enzymes that control the processes of photosynthesis can be denatured (where the active site changes shape and is no longer complementary to its substrate) – this reduces the overall rate

Graph showing the effect of temperature on the rate of photosynthesis

Light

• The intensity of the light available to the plant will depend on the amount of energy that it has to carry out photosynthesis
• The more light a plant receives, the faster the rate of photosynthesis
• This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply

 

Graph showing the effect of light intensity on the rate of photosynthesis

Carbon dioxide concentration

• Carbon dioxide is one of the raw materials required for photosynthesis
• This means the more carbon dioxide that is present, the faster the reaction can occur
• This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply

 

A graph showing the effect of the concentration of carbon dioxide on the rate of photosynthesis